Attributes

name

This is a string, with a minimum of 2 and a maximum of 50 characters (though shorter names are recommended), that defines the package name. It will be the <pkgName>/version@user/channel of the package reference. It should match the following regex ^[a-zA-Z0-9_][a-zA-Z0-9_\+\.-]{1,50}$, so start with alphanumeric or underscore, then alphanumeric, underscore, +, ., - characters.

The name is only necessary for export-ing the recipe into the local cache (export and create commands), if they are not defined in the command line. It might take its value from an environment variable, or even any python code that defines it (e.g. a function that reads an environment variable, or a file from disk). However, the most common and suggested approach would be to define it in plain text as a constant, or provide it as command line arguments.

version

The version attribute will define the version part of the package reference: pkgName/<version>@user/channel It is a string, and can take any value, matching the same constraints as the name attribute. In case the version follows semantic versioning in the form X.Y.Z-pre1+build2, that value might be used for requiring this package through version ranges instead of exact versions.

The version is only strictly necessary for export-ing the recipe into the local cache (export and create commands), if they are not defined in the command line. It might take its value from an environment variable, or even any python code that defines it (e.g. a function that reads an environment variable, or a file from disk). Please note that this value might be used in the recipe in other places (as in source() method to retrieve code from elsewhere), making this value not constant means that it may evaluate differently in different contexts (e.g., on different machines or for different users) leading to unrepeatable or unpredictable results. The most common and suggested approach would be to define it in plain text as a constant, or provide it as command line arguments.

description

This is an optional, but strongly recommended text field, containing the description of the package, and any information that might be useful for the consumers. The first line might be used as a short description of the package.

class HelloConan(ConanFile):
    name = "hello"
    version = "0.1"
    description = """This is a Hello World library.
                    A fully featured, portable, C++ library to say Hello World in the stdout,
                    with incredible iostreams performance"""

homepage

Use this attribute to indicate the home web page of the library being packaged. This is useful to link the recipe to further explanations of the library itself like an overview of its features, documentation, FAQ as well as other related information.

class EigenConan(ConanFile):
    name = "eigen"
    version = "3.3.4"
    homepage = "http://eigen.tuxfamily.org"

url

It is possible, even typical, if you are packaging a third party lib, that you just develop the packaging code. Such code is also subject to change, often via collaboration, so it should be stored in a VCS like git, and probably put on GitHub or a similar service. If you do indeed maintain such a repository, please indicate it in the url attribute, so that it can be easily found.

class HelloConan(ConanFile):
    name = "hello"
    version = "0.1"
    url = "https://github.com/conan-io/hello.git"

The url is the url of the package repository, i.e. not necessarily the original source code. It is optional, but highly recommended, that it points to GitHub, Bitbucket or your preferred code collaboration platform. Of course, if you have the conanfile inside your library source, you can point to it, and afterwards use the url in your source() method.

This is a recommended, but not mandatory attribute.

license

This field is intended for the license of the target source code and binaries, i.e. the code that is being packaged, not the conanfile.py itself. This info is used to be displayed by the conan info command and possibly other search and report tools.

class HelloConan(ConanFile):
    name = "hello"
    version = "0.1"
    license = "MIT"

This attribute can contain several, comma separated licenses. It is a text string, so it can contain any text, including hyperlinks to license files elsewhere.

However, we strongly recommend packagers of Open-Source projects to use SPDX identifiers from the SPDX license list instead of free-formed text. This will help people wanting to automate license compatibility checks, like consumers of your package, or you if your package has Open-Source dependencies.

This is a recommended, but not mandatory attribute.

author

Intended to add information about the author, in case it is different from the Conan user. It is possible that the Conan user is the name of an organization, project, company or group, and many users have permissions over that account. In this case, the author information can explicitly define who is the creator/maintainer of the package

class HelloConan(ConanFile):
    name = "hello"
    version = "0.1"
    author = "John J. Smith (john.smith@company.com)"

This is an optional attribute.

topics

Topics provide a useful way to group related tags together and to quickly tell developers what a package is about. Topics also make it easier for customers to find your recipe. It could be useful to filter packages by topics.

The topics attribute should be a tuple with the needed topics inside.

class ProtocInstallerConan(ConanFile):
    name = "protoc_installer"
    version = "0.1"
    topics = ("protocol-buffers", "protocol-compiler", "serialization", "rpc")

This is an optional attribute.

user, channel

These fields are optional in a Conan reference, they could be useful to identify a forked recipe from the community with changes specific for your company. Using these fields you may keep the same name and version and use the user/channel to disambiguate your recipe.

The value of these fields can be accessed from within a conanfile.py:

from conans import ConanFile

class HelloConan(ConanFile):
    name = "hello"
    version = "0.1"

    def requirements(self):
        self.requires("common-lib/version")
        if self.user and self.channel:
            # If the recipe is using them, I want to consume my fork.
            self.requires("say/0.1@%s/%s" % (self.user, self.channel))
        else:
            # otherwise, I'll consume the community one
            self.requires("say/0.1")

Only packages that have already been exported (packages in the local cache or in a remote server) can have a user/channel assigned. For package recipes working in the user space, there is no current user/channel by default, although they can be defined at conan install time with:

$ conan install <path to conanfile.py> user/channel

See also

FAQ: Is there any recommendation regarding which <user> or <channel> to use in a reference?

Warning

Environment variables CONAN_USERNAME and CONAN_CHANNEL that were used to assign a value to these fields are now deprecated and will be removed in Conan 2.0. Don’t use them to populate the value of self.user and self.channel.

default_user, default_channel

For package recipes working in the user space, with local methods like conan install . and conan build ., there is no current user/channel. If you are accessing to self.user or self.channel in your recipe, you need to declare the environment variables CONAN_USERNAME and CONAN_CHANNEL or you can set the attributes default_user and default_channel. You can also use python @property:

from conans import ConanFile

class HelloConan(ConanFile):
    name = "hello"
    version = "0.1"
    default_user = "myuser"

    @property
    def default_channel(self):
        return "mydefaultchannel"

    def requirements(self):
        self.requires("pkg/0.1@%s/%s" % (self.user, self.channel))

settings

There are several things that can potentially affect a package being created, i.e. the final package will be different (a different binary, for example), if some input is different.

Development project-wide variables, like the compiler, its version, or the OS itself. These variables have to be defined, and they cannot have a default value listed in the conanfile, as it would not make sense.

It is obvious that changing the OS produces a different binary in most cases. Changing the compiler or compiler version changes the binary too, which might have a compatible ABI or not, but the package will be different in any case.

For these reasons, the most common convention among Conan recipes is to distinguish binaries by the following four settings, which is reflected in the conanfile.py template used in the conan new command:

settings = "os", "compiler", "build_type", "arch"

When Conan generates a compiled binary for a package with a given combination of the settings above, it generates a unique ID for that binary by hashing the current values of these settings.

But what happens for example to header only libraries? The final package for such libraries is not binary and, in most cases it will be identical, unless it is automatically generating code. We can indicate that in the conanfile:

from conans import ConanFile

 class HelloConan(ConanFile):
     name = "hello"
     version = "0.1"
     # We can just omit the settings attribute too
     settings = None

     def build(self):
         #empty too, nothing to build in header only

You can restrict existing settings and accepted values as well, by redeclaring the settings attribute:

class HelloConan(ConanFile):
    settings = {"os": ["Windows"],
        "compiler": {"Visual Studio": {"version": [11, 12]}},
        "arch": None}

In this example we have just defined that this package only works in Windows, with VS 10 and 11. Any attempt to build it in other platforms with other settings will throw an error saying so. We have also defined that the runtime (the MD and MT flags of VS) is irrelevant for us (maybe we using a universal one?). Using None as a value means, maintain the original values in order to avoid re-typing them. Then, “arch”: None is totally equivalent to “arch”: [“x86”, “x86_64”, “arm”] Check the reference or your ~/.conan/settings.yml file.

As re-defining the whole settings attribute can be tedious, it is sometimes much simpler to remove or tune specific fields in the configure() method. For example, if our package is runtime independent in VS, we can just remove that setting field:

settings = "os", "compiler", "build_type", "arch"

def configure(self):
    self.settings.compiler["Visual Studio"].remove("runtime")

It is possible to check the settings to implement conditional logic, with attribute syntax:

def build(self):
    if self.settings.os == "Windows" and self.settings.compiler.version == "15":
        # do some special build commands
    elif self.settings.arch == "x86_64":
        # Other different commands

Those comparisons do content checking, for example if you do a typo like self.settings.os == "Windows", Conan will fail and tell you that is not a valid settings.os value, and the possible range of values.

Likewise, if you try to access some setting that doesn’t exist, like self.settings.compiler.libcxx for the Visual Studio setting, Conan will fail telling that libcxx does not exist for that compiler.

If you want to do a safe check of settings values, you could use the get_safe() method:

def build(self):
    # Will be None if doesn't exist
    arch = self.settings.get_safe("arch")
    # Will be None if doesn't exist
    compiler_version = self.settings.get_safe("compiler.version")
    # Will be the default version if the return is None
    build_type = self.settings.get_safe("build_type", default="Release")

The get_safe() method will return None if that setting or subsetting doesn’t exist and there is no default value assigned.

If you want to do a safe deletion of settings, you could use the rm_safe() method. For example, in the configure() method a typical pattern for a C library would be:

def configure(self):
    self.settings.rm_safe("compiler.libcxx")
    self.settings.rm_safe("compiler.cppstd")

options

Conan provides this attribute to declare traits which will affect only one reference, unlike the settings that are typically the same for all the recipes in a Conan graph. Options are declared per recipe, this attribute consist on a dictionary where the key is the option name and the value is the list of different values that the option can take.

Important

All the options with their values are encoded into the package ID, as everything that affects the generated binary. See configure(), config_options() and package_id() methods for information about removing certain options for some configurations.

A very common one is the option shared with allowed values of [True, False] that many recipes declare and use to configure the build system to produce a static library or a shared library.

Values for each option can be typed or plain strings ("value", True, None, 42,…) and there is a special value, "ANY", for options that can take any value. When an option uses "ANY", but its default value is None, then it should be added to the possible option values too.

class MyPkg(ConanFile):
    ...
    options = {
        "shared": [True, False],
        "option1": ["value1", "value2"],
        "option2": ["ANY"],
        "option3": [None, "value1", "value2"],
        "option4": [True, False, "value"],
        "option5": [None, "ANY"],
    }

Every option in a recipe needs to be assigned a value from the ones declared in the options attribute. The consumer can define options using different methods: command line, profile or consumer recipes; an uninitialized option will get the value None and it will be a valid value if it is contained in the list of valid values. Invalid values will produce an error. See attribute default_options for a way to declare a default value for options in a recipe.

Tip

• You can inspect available package options reading the package recipe, which can be done with the command conan inspect mypkg/0.1@user/channel.

Tip

• Options "shared": [True, False] and "fPIC": [True, False] are automatically managed in CMake and AutoToolsBuildEnvironment (configure/make) build helpers.

Define the value of an option

As we mentioned before, values for options in a recipe can be defined using different ways, let’s go over all of them for the example recipe mypkg defined above:

• In the recipe that declares the option:

  • Using the attribute default_options in the recipe itself.

  • In the config_options() method of the recipe.

  • In the configure() method of the recipe itself (this one has the highest precedence, this value can’t be overriden)

    class MyPkg(ConanFile):
    
        options = {
            "shared": [True, False],
            "option1": ["value1", "value2"],
            "option2": ["ANY"],
        }
    
        def configure(self):
            if some_condition:
                self.options.shared = False
    

• From a recipe that requires this one:

  • using the default_options attribute of the consumer:

    class OtherPkg(ConanFile):
        requires = "mypkg/0.1@user/channel"
        default_options = {"mypkg:shared": False}
    

  • in the configure() method of the consumer (highest precedence after configure() in the recipe itself):

    class OtherPkg(ConanFile):
        requires = "mypkg/0.1@user/channel"
    
        def configure(self):
            self.options['mypkg'].shared = False
    

    This method allows to assign values based on other conditions, it can have some drawbacks as it is explainded in the mastering section.

• In the conanfile.txt file:

  [requires]
  mypkg/0.1@user/channel
  
  [options]
  mypkg:shared=False
  

• It is also possible to define default values for the options of a recipe using profiles. They will apply whenever that recipe is used:

  [settings]
  setting=value
  
  [options]
  mypkg:shared=False
  

• Last way of defining values for options is to pass these values using the command argument -o,--option in the command line:

  $ conan install . -o mypkg:shared=True
  

Regarding the precedence of all these ways of assigning a value to an option, it works like any other configuration element in Conan: the closer to the consumer and the command line the higher the precedence. The list above is ordered from the less priority to the highest one (with the exceptional assignment in configure() method which cannot be overridden).

Get the value of an option

Values from options can be retrieved after they are assigned. For options that belong to the same recipe, the value can be retrieved in any method to run logic conditional to their values. Options from required packages can be retrieved only after the full graph has been resolved, this means that the value will be available in the methods validate(), build(), package(), package_info(). Accessing those values in other methods can lead to unexpected results.

class OtherPkg(ConanFile):
    requires = "mypkg/0.1@user/channel"

    def validate(self):
        if self.options['mypkg'].shared:
            raise ConanInvalidConfiguration("Cannot use shared library of requirement 'mypkg'")

If you want to retrieve the value of an option and fallback to a known value if the option doesn’t exist you can use the get_safe() method:

def build(self):
    # Will return None if doesn't exist
    fpic = self.options.get_safe("fPIC")
    # Will return the default value if the return is None
    shared = self.options.get_safe("shared", default=False)

The get_safe() method will return None if that option doesn’t exist and there is no default value assigned.

If you want to do a safe deletion of options, you could use the rm_safe() method. For example, in the config_options() method a typical pattern for Windows library would be:

def config_options(self):
    if self.settings.os == "Windows":
        self.options.rm_safe("fPIC")

Evaluate options

It is very important to know how the options are evaluated in conditional expressions and how the comparison operator works with them:

• Evaluation for the typed value and the string one is the same, so all these inputs would behave the same:

  • default_options = {"shared": True, "option": None}

  • default_options = {"shared": "True", "option": "None"}

  • mypkg:shared=True, mypkg:option=None on profiles, command line or conanfile.txt

• Implicit conversion to boolean is case insensitive, so the expression bool(self.options.option):

  • equals True for the values True, "True" and "true", and any other value that would be evaluated the same way in Python code.

  • equals False for the values False, "False" and "false", also for the empty string and for 0 and "0" as expected.

• Comparison using is is always equals to False because the types would be different as the option value is encapsulated inside a Python class.

• Explicit comparisons with the == symbol are case sensitive, so:

  • self.options.option = "False" satisfies assert self.options.option == False, assert self.options.option == "False", but assert self.options.option != "false".

• A different behavior has self.options.option = None, because assert self.options.option != None.

default_options

The attribute default_options has the purpose of defining the default values for the options if the consumer (consuming recipe, project, profile or the user through the command line) does not define them. This attribute should be defined as a python dictionary:

class MyPkg(ConanFile):
    ...
    options = {"build_tests": [True, False],
               "option1": ["value1", "value2"],
               "option2": ["ANY"],
               "option3": [None, "ANY"],
               }
    default_options = {"build_tests": True,
                       "option1": "value1",
                       "option2": 42,
                       "option3": None,
                       }

    def build(self):
        cmake = CMake(self)
        cmake.definitions['BUILD_TESTS'] = self.options.build_tests
        cmake.configure()
        ...

Remember that you can also assign default values for options of your requirements as we’ve seen in the attribute options.

You can also set the options conditionally to a final value with configure() instead of using default_options:

class OtherPkg(ConanFile):
    settings = "os", "arch", "compiler", "build_type"
    options = {"some_option": [True, False]}
    # Do NOT declare 'default_options', use 'config_options()'

    def configure(self):
        if self.options.some_option == None:
            if self.settings.os == 'Android':
                self.options.some_option = True
            else:
                self.options.some_option = False

Take into account that if a value is assigned in the configure() method it cannot be overridden.

Important

Default options can be specified as a dictionary only for Conan version >= 1.8.

See also

Read more about the config_options() method.

requires

Specify package dependencies as a list or tuple of other packages:

class MyLibConan(ConanFile):
    requires = "hello/1.0@user/stable", "OtherLib/2.1@otheruser/testing"

You can specify further information about the package requirements:

class MyLibConan(ConanFile):
    requires = [("hello/0.1@user/testing"),
                ("say/0.2@dummy/stable", "override"),
                ("bye/2.1@coder/beta", "private")]

class MyLibConan(ConanFile):
    requires = (("hello/1.0@user/stable", "private"), )

Requirements can be complemented by 2 different parameters:

private: a dependency can be declared as private if it is going to be fully embedded and hidden from consumers of the package. It might be necessary in some extreme cases, like having to use two different versions of the same library (provided that they are totally hidden in a shared library, for example), but it is mostly discouraged otherwise.

override: packages can define overrides of their dependencies, if they require the definition of specific versions of the upstream required libraries, but not necessarily direct dependencies. For example, a package can depend on A(v1.0), which in turn could conditionally depend on Zlib(v2), depending on whether the compression is enabled or not. Now, if you want to force the usage of Zlib(v3) you can:

class HelloConan(ConanFile):
    requires = ("ab/1.0@user/stable", ("zlib/3.0@other/beta", "override"))

This will not introduce a new dependency, it will just change zlib/2.0 to zlib/3.0 if ab actually requires it. Otherwise zlib will not be a dependency of your package.

Note

To prevent accidental override of transitive dependencies, check the config variable general.error_on_override or the environment variable CONAN_ERROR_ON_OVERRIDE.

version ranges

The syntax is using brackets:

class HelloConan(ConanFile):
    requires = "pkg/[>1.0 <1.8]@user/stable"

Expressions are those defined and implemented by [python node-semver](https://pypi.org/project/node-semver/). Accepted expressions would be:

>1.1 <2.1    # In such range
2.8          # equivalent to =2.8
~=3.0        # compatible, according to semver
>1.1 || 0.8  # conditions can be OR'ed

Go to Mastering/Version Ranges if you want to learn more about version ranges.

tool_requires

Tool requirements are requirements that are only installed and used when the package is built from sources. If there is an existing pre-compiled binary, then the tool requirements for this package will not be retrieved.

They can be specified as a comma separated tuple in the package recipe:

class MyPkg(ConanFile):
    tool_requires = "tool_a/0.2@user/testing", "tool_b/0.2@user/testing"

Read more: Tool requirements

exports

This optional attribute declares the set of files that should be exported and stored side by side with the conanfile.py file to make the recipe work: other python files that the recipe will import, some text file with data to read,…

The exports field can declare one single file or pattern, or a list of any of the previous elements. Patterns use fnmatch formatting to declare files to include or exclude.

For example, if we have some python code that we want the recipe to use in a helpers.py file, and have some text file info.txt we want to read and display during the recipe evaluation we would do something like:

exports = "helpers.py", "info.txt"

Exclude patterns are also possible, with the ! prefix:

exports = "*.py", "!*tmp.py"

exports_sources

This optional attribute declares the set of files that should be exported together with the recipe and will be available to generate the package. Unlike exports attribute, these files shouldn’t be used by the conanfile.py Python code, but to compile the library or generate the final package. And, due to its purpose, these files will only be retrieved if requested binaries are not available or the user forces Conan to compile from sources.

The exports_sources attribute can declare one single file or pattern, or a list of any of the previous elements. Patterns use fnmatch formatting to declare files to include or exclude.

Together with the source() and imports() methods, and the SCM feature, this is another way to retrieve the sources to create a package. Unlike the other methods, files declared in exports_sources will be exported together with the conanfile.py recipe, so, if nothing else is required, it can create a self-contained package with all the sources (like a snapshot) that will be used to generate the final artifacts.

Some examples for this attribute are:

exports_sources = "include*", "src*"

Exclude patterns are also possible, with the ! prefix:

exports_sources = "include*", "src*", "!src/build/*"

Note, if the recipe defines the layout() method and specifies a self.folders.source = "src" it won’t affect where the files (from the exports_sources) are copied. They will be copied to the base source folder. So, if you want to replace some file that got into the source() method, you need to explicitly copy it from the parent folder or even better, from self.export_sources_folder.

import os, shutil
from conan import ConanFile
from conan.tools.files import save, load

class Pkg(ConanFile):
   ...
   exports_sources = "CMakeLists.txt"

   def layout(self):
       self.folders.source = "src"
       self.folders.build = "build"

   def source(self):
       # emulate a download from web site
       save(self, "CMakeLists.txt", "MISTAKE: Very old CMakeLists to be replaced")
       # Now I fix it with one of the exported files
       shutil.copy("../CMakeLists.txt", ".")
       shutil.copy(os.path.join(self.export_sources_folder, "CMakeLists.txt", "."))

generators

Generators specify which is the output of the install command in your project folder. By default, a conanbuildinfo.txt file is generated, but you can specify different generators and even use more than one.

class MyLibConan(ConanFile):
    generators = "cmake", "gcc"

You can also set the generators conditionally in the configure() method like in the example below.

class MyLibConan(ConanFile):
    settings = "os", "compiler", "arch", "build_type"
    def configure(self):
        if self.settings.os == "Windows":
            self.generators = ["msbuild"]

Check the full generators list.

should_configure, should_build, should_install, should_test

Read only variables defaulted to True.

These variables allow you to control the build stages of a recipe during a conan build command with the optional arguments --configure/--build/--install/--test. For example, consider this build() method:

def build(self):
    cmake = CMake(self)
    cmake.configure()
    cmake.build()
    cmake.install()
    cmake.test()

If nothing is specified, all four methods will be called. But using command line arguments, this can be changed:

$ conan build . --configure  # only run cmake.configure(). Other methods will do nothing
$ conan build . --build      # only run cmake.build(). Other methods will do nothing
$ conan build . --install    # only run cmake.install(). Other methods will do nothing
$ conan build . --test       # only run cmake.test(). Other methods will do nothing
# They can be combined
$ conan build . -c -b # run cmake.configure() + cmake.build(), but not cmake.install() nor cmake.test()

Autotools and Meson helpers already implement the same functionality. For other build systems, you can use these variables in the build() method:

def build(self):
    if self.should_configure:
        # Run my configure stage
    if self.should_build:
        # Run my build stage
    if self.should_install: # If my build has install, otherwise use package()
        # Run my install stage
    if self.should_test:
        # Run my test stage

Note that the should_configure, should_build, should_install, should_test variables will always be True while building in the cache and can be only modified for the local flow with conan build.

build_policy

With the build_policy attribute the package creator can change conan’s build behavior. The allowed build_policy values are:

• missing: If this package is not found as a binary package, Conan will build it from source.

• always: This package will always be built from source, also retrieving the source code each time by executing the “source” method.

 class PocoTimerConan(ConanFile):
     build_policy = "always" # "missing"

short_paths

This attribute is specific to Windows, and ignored on other operating systems. It tells Conan to workaround the limitation of 260 chars in Windows paths.

Important

Since Windows 10 (ver. 10.0.14393), it is possible to enable long paths at the system level. Latest python 2.x and 3.x installers enable this by default. With the path limit removed both on the OS and on Python, the short_paths functionality becomes unnecessary, and can be disabled explicitly through the CONAN_USER_HOME_SHORT environment variable.

Enabling short paths management will “link” the source and build directories of the package to a different location, in Windows it will be C:\.conan\tmpdir. All the folder layout in the local cache is maintained.

Set short_paths=True in your conanfile.py:

from conans import ConanFile

class ConanFileTest(ConanFile):
    ...
    short_paths = True

See also

There is an environment variable CONAN_USE_ALWAYS_SHORT_PATHS to force activate this behavior for all packages.

This behavior will also work in Cygwin, the short folder directory will be /home/<user>/.conan_short by default, but it can be modified as we’ve explained before.

no_copy_source

The attribute no_copy_source tells the recipe that the source code will not be copied from the source folder to the build folder. This is mostly an optimization for packages with large source codebases or header-only, to avoid extra copies. It is mandatory that the source code must not be modified at all by the configure or build scripts, as the source code will be shared among all builds.

To be able to use it, the package recipe can access the self.source_folder attribute, which will point to the build folder when no_copy_source=False or not defined, and will point to the source folder when no_copy_source=True.

When this attribute is set to True, the self.copy() lines will be called twice, one copying from the source folder and the other copying from the build folder.

Read header-only section for an example using no_copy_source attribute.

source_folder

The folder in which the source code lives.

When a package is built in the Conan local cache its value is the same as the build folder by default. This is due to the fact that the source code is copied from the source folder to the build folder to ensure isolation and avoiding modifications of shared common source code among builds for different configurations. Only when no_copy_source=True this folder will actually point to the package source folder in the local cache.

When executing Conan commands in the Package development flow like conan source, this attribute will be pointing to the folder specified in the command line.

install_folder

The folder in which the installation of packages outputs the generator files with the information of dependencies. By default in the the local cache its value is the same as self.build_folder one.

When executing Conan commands in the Package development flow like conan install or conan build, this attribute will be pointing to the folder specified in the command line.

build_folder

The folder used to build the source code. In the local cache a build folder is created with the name of the package ID that will be built.

When executing Conan commands in the Package development flow like conan build, this attribute will be pointing to the folder specified in the command line.

package_folder

The folder to copy the final artifacts for the binary package. In the local cache a package folder is created for every different package ID.

When executing Conan commands in the Package development flow like conan package, this attribute will be pointing to the folder specified in the command line.

recipe_folder

Available since: 1.28.0

The folder where the recipe conanfile.py is stored, either in the local folder or in the cache. This is useful in order to access files that are exported along with the recipe.

cpp_info

Important

This attribute is only defined inside package_info() method being None elsewhere.

The self.cpp_info attribute is responsible for storing all the information needed by consumers of a package: include directories, library names, library paths… There are some default values that will be applied automatically if not indicated otherwise.

This object should be filled in package_info() method.

NAME	DESCRIPTION
self.cpp_info.includedirs	Ordered list with include paths. Defaulted to ["include"]
self.cpp_info.libdirs	Ordered list with lib paths. Defaulted to ["lib"]
self.cpp_info.resdirs	Ordered list of resource (data) paths. Defaulted to ["res"]. If layout() is declared, defaulted to [] *
self.cpp_info.bindirs	Ordered list with paths to binaries (executables, dynamic libraries,…). Defaulted to ["bin"]
self.cpp_info.builddirs	Ordered list with build scripts directory paths. Defaulted to [""] (Package folder directory) CMake generators will search in these dirs for files like findXXX.cmake
self.cpp_info.libs	Ordered list with the library names, Defaulted to [] (empty)
self.cpp_info.defines	Preprocessor definitions. Defaulted to [] (empty)
self.cpp_info.cflags	Ordered list with pure C flags. Defaulted to [] (empty)
self.cpp_info.cppflags	[DEPRECATED: Use cxxflags instead]
self.cpp_info.cxxflags	Ordered list with C++ flags. Defaulted to [] (empty)
self.cpp_info.sharedlinkflags	Ordered list with linker flags (shared libs). Defaulted to [] (empty)
self.cpp_info.exelinkflags	Ordered list with linker flags (executables). Defaulted to [] (empty)
self.cpp_info.frameworks	Ordered list with the framework names (OSX), Defaulted to [] (empty)
self.cpp_info.frameworkdirs	Ordered list with frameworks search paths (OSX). Defaulted to ["Frameworks"] or [] if layout() is declared *
self.cpp_info.rootpath	Filled with the root directory of the package, see deps_cpp_info
self.cpp_info.name	[DEPRECATED] Use self.cpp_info.names instead.
self.cpp_info.names[“generator”]	Alternative name for the package used by an specific generator to create files or variables. If set for a generator it will override the information provided by self.cpp_info.name. Like the cpp_info.name, this is only supported by cmake, cmake_multi, cmake_find_package, cmake_find_package_multi, cmake_paths and pkg_config generators.
self.cpp_info.filenames[“generator”]	Alternative name for the filename produced by a specific generator. If set for a generator it will override the “names” value. This is only supported by the cmake_find_package and cmake_find_package_multi generators.
self.cpp_info.system_libs	Ordered list with the system library names. Defaulted to [] (empty)
self.cpp_info.build_modules	Dictionary of lists per generator containing relative paths to build system related utility module files created by the package. Used by CMake generators to export .cmake files with functions for consumers. Defaulted to {} (empty)
self.cpp_info.components	[Experimental] Dictionary with different components a package may have: libraries, executables… Warning: Using components with other cpp_info non-default values or configs is not supported
self.cpp_info.requires	[Experimental] List of components to consume from requirements (it applies only to generators that implements components feature). Warning: If declared, only the components listed here will used by the linker and consumers.
self.cpp_info.objects	[Experimental] List of object libraries (.obj or .o). Defaulted to [] (empty) Only supported by new CMakeDeps generator

Note

(*) If the layout() is declared, for Conan >= 1.50, the default values for self.cpp_info.frameworkdirs and self.cpp_info.resdirs change to [], being a way to migrate to Conan 2.0, where the default values for these field changed. Read more in the migration guide.

The paths of the directories in the directory variables indicated above are relative to the self.package_folder directory.

Warning

Components is a experimental feature subject to breaking changes in future releases.

Using components you can achieve a more fine-grained control over individual libraries available in a single Conan package. Components allow you define a cpp_info like object per each of those libraries and also requirements between them and to components of other packages (the following case is not a real example):

def package_info(self):
    self.cpp_info.names["cmake_find_package"] = "OpenSSL"
    self.cpp_info.names["cmake_find_package_multi"] = "OpenSSL"
    self.cpp_info.components["crypto"].names["cmake_find_package"] = "Crypto"
    self.cpp_info.components["crypto"].libs = ["libcrypto"]
    self.cpp_info.components["crypto"].defines = ["DEFINE_CRYPTO=1"]
    self.cpp_info.components["crypto"].requires = ["zlib::zlib"]  # Depends on all components in zlib package

    self.cpp_info.components["ssl"].names["cmake"] = "SSL"
    self.cpp_info.components["ssl"].includedirs = ["include/headers_ssl"]
    self.cpp_info.components["ssl"].libs = ["libssl"]
    self.cpp_info.components["ssl"].requires = ["crypto",
                                                "boost::headers"]  # Depends on headers component in boost package
    self.cpp_info.components["ssl"].names["cmake"] = "SSL"

    obj_ext = "obj" if platform.system() == "Windows" else "o"
    self.cpp_info.components["ssl-objs"].objects = [os.path.join("lib", "ssl-object.{}".format(obj_ext))]

The interface of the Component object is the same as the one used by the cpp_info object and has the same default directories.

Warning

Using components and global cpp_info non-default values or release/debug configurations at the same time is not allowed (except for self.cpp_info.names).

Dependencies among components and to components of other requirements can be defined using the requires attribute and the name of the component. The dependency graph for components will be calculated and values will be aggregated in the correct order for each field.

New properties model for the cpp_info new tools

Warning

Using set_property and get_property methods for cpp_info is an experimental feature subject to breaking changes in future releases.

Using .names, .filenames and .build_modules will not work any more for new generators, like CMakeDeps and PkgConfigDeps. They have a new way of setting this information using set_property and get_property methods of the cpp_info object (available since Conan 1.36).

def set_property(self, property_name, value)
def get_property(self, property_name):

To read more about the new set_property and get_property methods for cpp_info please check the dedicated section in the Conan 2.0 migration guide.

deps_cpp_info

Contains the cpp_info object of the requirements of the recipe. In addition of the above fields, there are also properties to obtain the absolute paths, and name and version attributes:

NAME	DESCRIPTION
self.deps_cpp_info[“dep”].include_paths	“dep” package includedirs but transformed to absolute paths
self.deps_cpp_info[“dep”].lib_paths	“dep” package libdirs but transformed to absolute paths
self.deps_cpp_info[“dep”].bin_paths	“dep” package bindirs but transformed to absolute paths
self.deps_cpp_info[“dep”].build_paths	“dep” package builddirs but transformed to absolute paths
self.deps_cpp_info[“dep”].res_paths	“dep” package resdirs but transformed to absolute paths
self.deps_cpp_info[“dep”].framework_paths	“dep” package frameworkdirs but transformed to absolute paths
self.deps_cpp_info[“dep”].build_modules_paths	“dep” package build_modules but transformed to absolute paths
self.deps_cpp_info[“dep”].get_name(“<generator>”)	Get the name declared for the given generator
self.deps_cpp_info[“dep”].version	Get the version of the “dep” package
self.deps_cpp_info[“dep”].components	[Experimental] Dictionary with different components a package may have: libraries, executables…

To get a list of all the dependency names from deps_cpp_info, you can call the deps member:

class PocoTimerConan(ConanFile):
    ...
    def build(self):
        # deps is a list of package names: ["poco", "zlib", "openssl"]
        deps = self.deps_cpp_info.deps

It can be used to get information about the dependencies, like used compilation flags or the root folder of the package:

 class PocoTimerConan(ConanFile):
     ...
     requires = "zlib/1.2.11", "openssl/1.0.2u"
     ...

     def build(self):
         # Get the directory where zlib package is installed
         self.deps_cpp_info["zlib"].rootpath

         # Get the absolute paths to zlib include directories (list)
         self.deps_cpp_info["zlib"].include_paths

         # Get the sharedlinkflags property from OpenSSL package
         self.deps_cpp_info["openssl"].sharedlinkflags

Note

If using the experimental feature with different context for host and build, this attribute will contain only information from packages in the host context.

env_info

This attribute is only defined inside package_info() method, being None elsewhere, so please use it only inside this method.

The self.env_info object can be filled with the environment variables to be declared in the packages reusing the recipe.

See also

Read package_info() method docs for more info.

deps_env_info

You can access to the declared environment variables of the requirements of the recipe.

Note: The environment variables declared in the requirements of a recipe are automatically applied and it can be accessed with the python os.environ dictionary. Nevertheless if you want to access to the variable declared by some specific requirement you can use the self.deps_env_info object.

 import os

 class RecipeConan(ConanFile):
     ...
     requires = "package1/1.0@conan/stable", "package2/1.2@conan/stable"
     ...

     def build(self):
         # Get the SOMEVAR environment variable declared in the "package1"
         self.deps_env_info["package1"].SOMEVAR

         # Access to the environment variables globally
         os.environ["SOMEVAR"]

Note

If using the experimental feature with different context for host and build, this attribute will contain only information from packages in the build context.

user_info

This attribute is only defined inside package_info() method, being None elsewhere, so please use it only inside this method.

The self.user_info object can be filled with any custom variable to be accessed in the packages reusing the recipe.

See also

Read package_info() method docs for more info.

deps_user_info

You can access the declared user_info.XXX variables of the requirements through the self.deps_user_info object like this:

 import os

 class RecipeConan(ConanFile):
     ...
     requires = "package1/1.0@conan/stable"
     ...

     def build(self):
         self.deps_user_info["package1"].SOMEVAR

Note

If using the experimental feature with different context for host and build, this attribute will contain only information from packages in the host context. Use user_info_build to access information from packages that belong to build context.

user_info_build

Warning

This section refers to the experimental feature that is activated when using --profile:build and --profile:host in the command-line. It is currently under development, features can be added or removed in the following versions.

This attribute offers the information declared in the user_info.XXXX variables of the requirements that belong to the build context, it is available only if Conan is invoked with two profiles (see this section to know more about this feature.

 import os

 class RecipeConan(ConanFile):
     ...
     tool_requires = "tool/1.0"
     ...

     def build(self):
         self.user_info_build["tool"].SOMEVAR

info

Object used to control the unique ID for a package. Check the package_id() to see the details of the self.info object.

apply_env

When True (Default), the values from self.deps_env_info (corresponding to the declared env_info in the requires and tool_requires) will be automatically applied to the os.environ.

Disable it setting apply_env to False if you want to control by yourself the environment variables applied to your recipes.

You can apply manually the environment variables from the requires and tool_requires:

 import os
 from conans import tools

 class RecipeConan(ConanFile):
     apply_env = False

     def build(self):
         with tools.environment_append(self.env):
             # The same if we specified apply_env = True
             pass

in_local_cache

A boolean attribute useful for conditional logic to apply in user folders local commands. It will return True if the conanfile resides in the local cache ( we are installing the package) and False if we are running the conanfile in a user folder (local Conan commands).

import os

class RecipeConan(ConanFile):
    ...

    def build(self):
        if self.in_local_cache:
            # we are installing the package
        else:
            # we are building the package in a local directory

develop

A boolean attribute useful for conditional logic. It will be True if the package is created with conan create, or if the conanfile.py is in user space:

class RecipeConan(ConanFile):

    def build(self):
        if self.develop:
            self.output.info("Develop mode")

It can be used for conditional logic in other methods too, like requirements(), package(), etc.

This recipe will output “Develop mode” if:

$ conan create . user/testing
# or
$ mkdir build && cd build && conan install ..
$ conan build ..

But it will not output that when it is a transitive requirement or installed with conan install.

keep_imports

Just before the build() method is executed, if the conanfile has an imports() method, it is executed into the build folder, to copy binaries from dependencies that might be necessary for the build() method to work. After the method finishes, those copied (imported) files are removed, so they are not later unnecessarily repackaged.

This behavior can be avoided declaring the keep_imports=True attribute. This can be useful, for example to repackage artifacts

scm

Warning

This is an experimental feature subject to breaking changes in future releases. Although this is an experimental feature, the use of the feature using scm_to_conandata is considered stable.

Used to clone/checkout a repository. It is a dictionary with the following possible values:

from conans import ConanFile, CMake, tools

class HelloConan(ConanFile):
     scm = {
        "type": "git",
        "subfolder": "hello",
        "url": "https://github.com/conan-io/hello.git",
        "revision": "master"
     }
    ...

• type (Required): Currently only git and svn are supported. Others can be added eventually.

• url (Required): URL of the remote or auto to capture the remote from the local working copy (credentials will be removed from it). When type is svn it can contain the peg_revision.

• revision (Required): id of the revision or auto to capture the current working copy one. When type is git, it can also be the branch name or a tag.

• subfolder (Optional, Defaulted to .): A subfolder where the repository will be cloned.

• username (Optional, Defaulted to None): When present, it will be used as the login to authenticate with the remote.

• password (Optional, Defaulted to None): When present, it will be used as the password to authenticate with the remote.

• verify_ssl (Optional, Defaulted to True): Verify SSL certificate of the specified url.

• shallow (Optional, Defaulted to True): Use shallow clone for Git repositories.

• submodule (Optional, Defaulted to None):

  • shallow: Will sync the git submodules using submodule sync

  • recursive: Will sync the git submodules using submodule sync --recursive

Attributes type, url and revision are required to upload the recipe to a remote server.

SCM attributes are evaluated in the working directory where the conanfile.py is located before exporting it to the Conan cache, so these values can be returned from arbitrary functions that depend on the local directory. Nevertheless, all the other code in the recipe must be able to run in the export folder inside the cache, where it has access only to the files exported (see attribute exports and conandata.yml) and to any other functionality from a python_requires package.

Warning

By default, in Conan v1.x the information after evaluating the attribute scm will be stored in the conanfile.py file (the recipe will be modified when exported to the Conan cache) and any value will be written in plain text (watch out about passwords). However, you can activate the scm_to_conandata config option, the conanfile.py won’t be modified (data is stored in a different file) and the fields username and password won’t be stored, so these one will be computed each time the recipe is loaded.

Note

In case of git, by default conan will try to perform shallow clone of the repository, and will fallback to the full clone in case shallow fails (e.g. not supported by the server).

To know more about the usage of scm check:

• Creating packages/Recipe and sources in a different repo

• Creating packages/Recipe and sources in the same repo

revision_mode

Warning

This attribute is part of the package revisions feature, so it is also an experimental feature subject to breaking changes in future releases.

This attribute allow each recipe to declare how the revision for the recipe itself should be computed. It can take two different values:

• "hash" (by default): Conan will use the checksum hash of the recipe manifest to compute the revision for the recipe.

• "scm": the commit ID will be used as the recipe revision if it belongs to a known repository system (Git or SVN). If there is no repository it will raise an error.

python_requires (legacy)

Warning

This attribute has been superseded by the new Python requires. Even if this is an experimental feature subject to breaking changes in future releases, this legacy python_requires syntax has not been removed yet, but it will be removed in Conan 2.0.

Python requires are associated with the ConanFile declared in the recipe file, data from those imported recipes is accessible using the python_requires attribute in the recipe itself. This attribute is a dictionary where the key is the name of the python requires reference and the value is a dictionary with the following information:

• ref: full reference of the python requires.

• exports_folder: directory in the cache where the exported files are located.

• exports_sources_folder: directory in the cache where the files exported using the exports_sources attribute of the python requires recipe are located.

You can use this information to copy files accompanying a python requires to the consumer workspace.:

from conans import ConanFile

class PyReq(ConanFile):
    name = "pyreq"
    exports_sources = "CMakeLists.txt"

    def source(self):
        pyreq = self.python_requires['pyreq']
        path = os.path.join(pyreq.exports_sources_folder, "CMakeLists.txt")
        shutil.copy(src=path, dst=self.source_folder)

python_requires

Warning

This is an experimental feature subject to breaking changes in future releases.

This class attribute allows to define a dependency to another Conan recipe and reuse its code. Its basic syntax is:

from conans import ConanFile

class Pkg(ConanFile):
    python_requires = "pyreq/0.1@user/channel"  # recipe to reuse code from

    def build(self):
        self.python_requires["pyreq"].module # access to the whole conanfile.py module
        self.python_requires["pyreq"].module.myvar  # access to a variable
        self.python_requires["pyreq"].module.myfunct()  # access to a global function
        self.python_requires["pyreq"].path # access to the folder where the reused file is

Read more about this attribute in Python requires

python_requires_extend

Warning

This is an experimental feature subject to breaking changes in future releases.

This class attribute defines one or more classes that will be injected in runtime as base classes of the recipe class. Syntax for each of these classes should be a string like pyreq.MyConanfileBase where the pyreq is the name of a python_requires and MyConanfileBase is the name of the class to use.

from conans import ConanFile

class Pkg(ConanFile):
    python_requires = "pyreq/0.1@user/channel", "utils/0.1@user/channel"
    python_requires_extend = "pyreq.MyConanfileBase", "utils.UtilsBase"  # class/es to inject

Read more about this attribute in Python requires

conan_data

This attribute is a dictionary with the keys and values provided in a conandata.yml file format placed next to the conanfile.py. This YAML file is automatically exported with the recipe and automatically loaded with it too.

You can declare information in the conandata.yml file and then access it inside any of the methods of the recipe. For example, a conandata.yml with information about sources that looks like this:

sources:
  "1.1.0":
    url: "https://www.url.org/source/mylib-1.0.0.tar.gz"
    sha256: "8c48baf3babe0d505d16cfc0cf272589c66d3624264098213db0fb00034728e9"
  "1.1.1":
    url: "https://www.url.org/source/mylib-1.0.1.tar.gz"
    sha256: "15b6393c20030aab02c8e2fe0243cb1d1d18062f6c095d67bca91871dc7f324a"

def source(self):
    tools.get(**self.conan_data["sources"][self.version])

deprecated

Warning

This is an experimental feature subject to breaking changes in future releases.

Available since: 1.28.0

This attribute declares that the recipe is deprecated, causing a user-friendly warning message to be emitted whenever it is used. For example, the following code:

from conans import ConanFile

class Pkg(ConanFile):
    name = "cpp-taskflow"
    version = "1.0"
    deprecated = True

may emit a warning like:

cpp-taskflow/1.0: WARN: Recipe 'cpp-taskflow/1.0' is deprecated. Please, consider changing your requirements.

Optionally, the attribute may specify the name of the suggested replacement:

from conans import ConanFile

class Pkg(ConanFile):
    name = "cpp-taskflow"
    version = "1.0"
    deprecated = "taskflow"

This will emit a warning like:

cpp-taskflow/1.0: WARN: Recipe 'cpp-taskflow/1.0' is deprecated in favor of 'taskflow'. Please, consider changing your requirements.

If the value of the attribute evaluates to False, no warning is printed.

provides

Warning

This is an experimental feature subject to breaking changes in future releases.

Available since: 1.28.0

This attribute declares that the recipe provides the same functionality as other recipe(s). The attribute is usually needed if two or more libraries implement the same API to prevent link-time and run-time conflicts (ODR violations). One typical situation is forked libraries.

Some examples are:

• LibreSSL, BoringSSL and OpenSSL

• libav and ffmpeg

• MariaDB client and MySQL client

If Conan encounters two or more libraries providing the same functionality within a single graph, it raises an error:

At least two recipes provides the same functionality:
 - 'libjpeg' provided by 'libjpeg/9d', 'libjpeg-turbo/2.0.5'

The attribute value should be a string with a recipe name or a tuple of such recipe names.

For example, to declare that libjpeg-turbo recipe offers the same functionality as libjpeg recipe, the following code could be used:

from conans import ConanFile

class LibJpegTurbo(ConanFile):
    name = "libjpeg-turbo"
    version = "1.0"
    provides = "libjpeg"

To declare that a recipe provides the functionality of several different recipes at the same time, the following code could be used:

from conans import ConanFile

class OpenBLAS(ConanFile):
    name = "openblas"
    version = "1.0"
    provides = "cblas", "lapack"

If the attribute is omitted, the value of the attribute is assumed to be equal to the current package name. Thus, it’s redundant for libjpeg recipe to declare that it provides libjpeg, it’s already implicitly assumed by Conan.

conf

Warning

This is an experimental feature subject to breaking changes in future releases.

Available since: 1.47.0

In the self.conf attribute we can find all the conf entries declared in the [conf] section of the profiles in addition of the declared self.conf_info entries from the first level tool requirements. The profile entries have priority.

This is an example of a recipe for a tool called my_android_ndk with the following recipe:

from conan import ConanFile

class MyAndroidNDKRecipe(ConanFile):

  name="my_android_ndk"
  version="1.0"

  def package_info(self):
      self.conf_info.define("tools.android:ndk_path", "bar")

If we require that tool:

from conan import ConanFile

class MyConsumer(ConanFile):

  tool_requires = "my_android_ndk/1.0"

  def generate(self):
      self.output.info("NDK host: %s" % self.conf.get("tools.android:ndk_path"))
      self.output.info("Custom var1: %s" % self.conf.get("user.custom.var1"))

And we install it applying this profile:

myprofile

include(default)
[conf]
tools.android:ndk_path=foo
user.custom.var1=hello

$ conan install . --profile myprofile
...
conanfile.py: Applying build-requirement: my_android_ndk/1.0
conanfile.py: Generator txt created conanbuildinfo.txt
conanfile.py: Calling generate()
conanfile.py: NDK host: foo
conanfile.py: Custom var1: hello
...

Without the profile:

$ conan install .
...
conanfile.py: Applying build-requirement: my_android_ndk/1.0
conanfile.py: Generator txt created conanbuildinfo.txt
conanfile.py: Calling generate()
conanfile.py: NDK host: bar
conanfile.py: Custom var1: None

win_bash

Warning

This is an experimental feature subject to breaking changes in future releases.

Available since: 1.39.0

When True it enables the new run in a subsystem bash in Windows mechanism. Read more here.

from conans import ConanFile

class FooRecipe(ConanFile):
    ...
    win_bash = True

test_type

Warning

Test type is an experimental feature subject to breaking changes in future releases.

Available since: 1.44.0

This attribute allows testing requirements and build requiments explicitly on test package. In Conan 2.0 the test_type attribute will be ignored, the behavior will be always explicit, so declaring test_type="explicit" will make the test recipe compatible with Conan 2.0. The possible values are:

• requires (default): The package being tested will be consumed as a regular requirement automatically.

• build_requires: The package being tested will be consumed as a build requirement automatically. It can be combined with requires to be required in both ways.

• explicit: The test package will not solve its dependencies automatically, you need to declare it explicitly using the reference at self.tested_reference_str. This will be the only behavior for Conan 2.0. The additional values requires and build_requires (if specified) will be ignored.

To solve build requirements and requirements automatically as regularly on Conan 1.0

from conans import ConanFile, CMake
import os

class TestPackage(ConanFile):
    test_type = "build_requires", "requires"

    def build(self):
        cmake = CMake(self)
        cmake.configure()
        cmake.build()

    def test(self):
        bin_path = os.path.join("bin", "test_package")
        self.run(bin_path, run_environment=True)

To explicitly declare the required dependencies as required on Conan 2.0:

from conans import ConanFile, CMake
import os

class TestPackage(ConanFile):
    test_type = "explicit"

    def requirements(self):
        self.requires(self.tested_reference_str)
        # and, or
        self.build_requires(self.tested_reference_str)

    def build(self):
        cmake = CMake(self)
        cmake.configure()
        cmake.build()

    def test(self):
        bin_path = os.path.join("bin", "test_package")
        self.run(bin_path, run_environment=True)

For more information see explicit test package requirement and testing tool requirements.