.. _reference_conanfile_methods_validate:


validate()
==========

The ``validate()`` method can be used to mark a package binary as "invalid", or not working for the current configuration. For example, if we have a header-only library that doesn't work in Windows, we could have the 
following ``conanfile.py``:

.. code-block:: python

    from conan import ConanFile
    from conan.errors import ConanInvalidConfiguration

    class Pkg(ConanFile):
        name = "pkg"
        version = "1.0"
        package_type = "header-library"
        settings = "os"

        def validate(self):
            if self.settings.os == "Windows":
                raise ConanInvalidConfiguration("Windows not supported")
        
        def package_id(self):
            self.info.clear()  # header-only

If we try to create this package in Windows, it will fail, but if we do it in Linux, it will succeed:

.. code-block:: bash

    $ conan create . -s os=Windows # FAILS
    ...
    ERROR: There are invalid packages:
    pkg/1.0: Invalid: Windows not supported
    $ conan create . -s os=Linux # WORKS

And if we try to use it in Windows, it will fail again:

.. code-block:: bash

    $ conan install --requires=pkg/1.0 -s os=Windows # FAILS
    ...
    ERROR: There are invalid packages:
    pkg/1.0: Invalid: Windows not supported

When the ``ConanInvalidConfiguration`` causes an error, Conan application exit code will be ``6``

It is possible to check the validity of a given graph without raising errors with the ``conan graph info`` command:

.. code-block:: bash
    :emphasize-lines: 7

    $ conan graph info --requires=pkg/1.0 -s os=Windows --filter=binary
    conanfile:
    ref: conanfile
    binary: None
    pkg/1.0#cfc18fcc7a50ead278a7c1820be74e56:
    ref: pkg/1.0#cfc18fcc7a50ead278a7c1820be74e56
    binary: Invalid


The ``validate()`` method is evaluated after the whole graph has been computed. This means that it can use the ``self.dependencies`` information to raise errors:

.. code-block:: python

    from conan import ConanFile
    from conan.errors import ConanInvalidConfiguration

    class Pkg(ConanFile):
        requires = "dep/0.1"

        def validate(self):
            if self.dependencies["dep"].options.myoption == 2:
                raise ConanInvalidConfiguration("Option 2 of 'dep' not supported")


.. note:: 

    **Best practices**

    The ``configure()`` method evaluates before the graph is complete, so it doesn't have the real values of the dependencies ``options``. The ``validate()`` method is the one that should be checking those dependencies options values if necessary, not ``configure()``.


.. seealso::

    - Follow the :ref:`tutorial about preparing build from source in recipes<creating_packages_preparing_the_build>`.