ref-manual: add pypi class

Add missing documentation for the pypi class.

(From yocto-docs rev: d387ca891ad3a7d00ec3cb5f994dc5832c885d54)

Signed-off-by: Paul Eggleton <paul.eggleton@microsoft.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/classes.rst

@@ -2005,6 +2005,21 @@ When inherited by a recipe, the ``perlnative`` class supports using the
 native version of Perl built by the build system rather than using the
 version provided by the build host.
 
+.. _ref-classes-pypi:
+
+``pypi.bbclass``
+================
+
+The ``pypi`` class sets variables appropriately for recipes that build
+Python modules from `PyPI <https://pypi.org/>`__, the Python Package Index.
+By default it determines the PyPI package name based upon :term:`BPN`
+(stripping the "python-" or "python3-" prefix off if present), however in
+some cases you may need to set it manually in the recipe by setting
+:term:`PYPI_PACKAGE`.
+
+Variables set by the ``pypi`` class include :term:`SRC_URI`, :term:`SECTION`,
+:term:`HOMEPAGE`, :term:`UPSTREAM_CHECK_URI`, and :term:`UPSTREAM_CHECK_REGEX`.
+
 .. _ref-classes-python_flit_core:
 
 ``python_flit_core.bbclass``

documentation/ref-manual/variables.rst

@@ -6177,6 +6177,14 @@ system and gives an overview of their function and contents.
 
       :term:`PV` is the default value of the :term:`PKGV` variable.
 
+   :term:`PYPI_PACKAGE`
+      When inheriting the :ref:`pypi <ref-classes-pypi>` class, specifies the
+      `PyPI <https://pypi.org/>`__ package name to be built. The default value
+      is set based upon :term:`BPN` (stripping any "python-" or "python3-"
+      prefix off if present), however for some packages it will need to be set
+      explicitly if that will not match the package name (e.g. where the
+      package name has a prefix, underscores, uppercase letters etc.)
+
    :term:`PYTHON_ABI`
       When used by recipes that inherit the
       :ref:`setuptools3 <ref-classes-setuptools3>` class, denotes the