Add one-line summary to some warnings

changelog.d/3328.misc.rst

@@ -0,0 +1 @@
+Include a first line summary to some of the existing multi-line warnings.

setuptools/command/build_py.py

@@ -256,6 +256,7 @@ class _IncludePackageDataAbuse:
     """Inform users that package or module is included as 'data file'"""
 
     MESSAGE = """\
+    Installing {importable!r} as data is deprecated, please list it in `packages`.
     !!\n\n
     ############################
     # Package would be ignored #
@@ -266,7 +267,9 @@ class _IncludePackageDataAbuse:
     therefore is considered deprecated).
 
     Please make sure that {importable!r} is included as a package by using
-    setuptools' `packages` configuration field or the proper discovery methods.
+    setuptools' `packages` configuration field or the proper discovery methods
+    (for example by using `find_namespace_packages(...)`/`find_namespace:`
+    instead of `find_packages(...)`/`find:`).
 
     You can read more about "package discovery" and "data files" on setuptools
     documentation page.

setuptools/command/dist_info.py

@@ -54,7 +54,8 @@ def _version(version: str) -> str:
     try:
         return str(packaging.version.Version(v)).replace("-", "_")
     except packaging.version.InvalidVersion:
-        msg = f"""!!\n\n
+        msg = f"""Invalid version: {version!r}.
+        !!\n\n
         ###################
         # Invalid version #
         ###################

setuptools/config/_apply_pyprojecttoml.py

@@ -341,7 +341,10 @@ def _acessor(obj):
 
 
 class _WouldIgnoreField(UserWarning):
-    """Inform users that ``pyproject.toml`` would overwrite previously defined metadata:
+    """Inform users that ``pyproject.toml`` would overwrite previous metadata."""
+
+    MESSAGE = """\
+    {field!r} defined outside of `pyproject.toml` would be ignored.
     !!\n\n
     ##########################################################################
     # configuration would be ignored/result in error due to `pyproject.toml` #
@@ -369,5 +372,4 @@ class _WouldIgnoreField(UserWarning):
     @classmethod
     def message(cls, field, value):
         from inspect import cleandoc
-        msg = "\n".join(cls.__doc__.splitlines()[1:])
-        return cleandoc(msg.format(field=field, value=value))
+        return cleandoc(cls.MESSAGE.format(field=field, value=value))

setuptools/config/pyprojecttoml.py

@@ -418,7 +418,7 @@ class _ExperimentalProjectMetadata(UserWarning):
 
 
 class _InvalidFile(UserWarning):
-    """Inform users that the given `pyproject.toml` is experimental:
+    """The given `pyproject.toml` file is invalid and would be ignored.
     !!\n\n
     ############################
     # Invalid `pyproject.toml` #
@@ -436,5 +436,4 @@ class _InvalidFile(UserWarning):
     @classmethod
     def message(cls):
         from inspect import cleandoc
-        msg = "\n".join(cls.__doc__.splitlines()[1:])
-        return cleandoc(msg)
+        return cleandoc(cls.__doc__)