Better documentation on the packaging breaking changes

Closes pylint-dev#4399

ChangeLog

@@ -9,6 +9,9 @@ Release date: TBA
 ..
   Put new features and bugfixes here and also in 'doc/whatsnew/2.9.rst'
 
+* Fixed some breaking change in 2.8.0, that we did not really have to do. The 'doc' extra-require and ``dependency_links``
+  and ``scripts`` from ``__pkginfo__`` are still removed.
+
 
 What's New in Pylint 2.8.0?
 ===========================
@@ -46,7 +49,7 @@ Release date: 2021-04-24
 * The 'doc' extra-require has been removed.
 
 * ``__pkginfo__`` now only contain ``__version__`` (also accessible with ``pylint.__version__``), other meta-information are still
-  accessible with ``import importlib;metadata.metadata('pylint')``.
+  accessible with ``from importlib import metadata;metadata.metadata('pylint')``.
 
 * COPYING has been renamed to LICENSE for standardization.
 

doc/whatsnew/2.8.rst

@@ -8,6 +8,17 @@
 Summary -- Release highlights
 =============================
 
+Breaking changes
+================
+
+* The 'doc' extra-require has been removed. ``dependency_links`` and ``scripts`` have been removed from ``__pkginfo__``.
+  Meta-information are accessible with
+
+```python
+from importlib import metadata
+metadata.metadata('pylint')
+```
+Prefer that to an import from ``__pkginfo__``.
 
 New checkers
 ============
@@ -43,9 +54,6 @@ Other Changes
 * The packaging is now done via setuptools exclusively. ``doc``, ``tests``, ``man``, ``elisp`` and ``Changelog`` are
   not packaged anymore - reducing the size of the package by 75%.
 
-* The 'doc' extra-require has been removed. ``pylint.version`` is now ``pylint.__version__`` and ``__pkginfo__`` does
-  not contain the package metadata anymore.
-
 * Updated ``astroid`` to 2.5.4
 
 * COPYING has been renamed to LICENSE for standardization.

pylint/__init__.py

@@ -74,4 +74,5 @@ def modify_sys_path() -> None:
         sys.path.pop(1)
 
 
-__all__ = ["__version__"]
+version = __version__
+__all__ = ["__version__", "version"]

pylint/__pkginfo__.py

@@ -1,6 +1,7 @@
 # Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 # For details: https://github.com/PyCQA/pylint/blob/master/LICENSE
 
+from importlib import metadata
 from typing import Optional
 
 __version__ = "2.8.1"
@@ -13,3 +14,24 @@
         __version__ += f"a{dev_version}"
     else:
         __version__ += f".dev{dev_version}"
+
+
+# Kept for compatibility reason, see https://github.com/PyCQA/pylint/issues/4399
+pylint_info = metadata.metadata("pylint")
+classifiers = []
+project_urls = []
+for header in pylint_info._headers:  # type: ignore
+    key, value = header
+    if key == "Project-URL":
+        project_urls.append(value)
+    if key == "Classifier":
+        classifiers.append(value)
+mailinglist = "mailto:[email protected]"
+numversion = pylint_info["version"].split(".")
+version = pylint_info["version"]
+install_requires = pylint_info["install_requires"]
+license = pylint_info["license"]  # pylint: disable=redefined-builtin # noqa
+description = pylint_info["Keywords"]
+web = pylint_info["Home-page"]
+author = pylint_info["Author"]
+author_email = pylint_info["Author-email"]