Petr's review

Author: StanFromIreland

Doc/using/configure.rst

@@ -261,8 +261,8 @@ General Options
    containing custom error messages for missing :term:`standard library` modules.
 
    This option is intended for Python distributors who wish to provide
-   distribution-specific guidance when users encounter missing standard library
-   modules that are packaged separately.
+   distribution-specific guidance when users encounter standard library
+   modules that are missing or packaged separately.
 
    The JSON file should map missing module names to custom error message strings.
    For example, if your distribution packages :mod:`tkinter` and

Doc/whatsnew/3.15.rst

@@ -229,13 +229,6 @@ Improved error messages
      AttributeError: 'Container' object has no attribute 'area'. Did you mean: 'inner.area'?
 
 
-* The new configure option :option:`--with-missing-stdlib-config=FILE` allows
-  distributors to pass a `JSON <https://www.json.org/json-en.html>`_
-  configuration file containing custom error messages for missing
-  :term:`standard library` modules.
-  (Contributed by Stan Ulbrych and Petr Viktorin in :gh:`139707`.)
-
-
 Other language changes
 ======================
 
@@ -1062,6 +1055,12 @@ Build changes
   set to ``no`` or with :option:`!--without-system-libmpdec`.
   (Contributed by Sergey B Kirpichev in :gh:`115119`.)
 
+* The new configure option :option:`--with-missing-stdlib-config=FILE` allows
+  distributors to pass a `JSON <https://www.json.org/json-en.html>`_
+  configuration file containing custom error messages for :term:`standard library`
+  modules that are missing or packaged separately.
+  (Contributed by Stan Ulbrych and Petr Viktorin in :gh:`139707`.)
+
 
 Porting to Python 3.15
 ======================

Lib/traceback.py

@@ -17,7 +17,7 @@
 try:
     from _stdlib_modules_info import MISSING_STDLIB_MODULE_MESSAGES
 except ImportError:
-    MISSING_STDLIB_MODULE_MESSAGES = None
+    MISSING_STDLIB_MODULE_MESSAGES = {}
 
 __all__ = ['extract_stack', 'extract_tb', 'format_exception',
            'format_exception_only', 'format_list', 'format_stack',
@@ -1115,14 +1115,11 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
         elif exc_type and issubclass(exc_type, ModuleNotFoundError):
             module_name = getattr(exc_value, "name", None)
             if module_name in sys.stdlib_module_names:
-                if MISSING_STDLIB_MODULE_MESSAGES is not None:
-                    message = MISSING_STDLIB_MODULE_MESSAGES.get(
-                        module_name,
-                        f"Standard library module {module_name!r} was not found"
-                    )
-                    self._str = message
-                else:
-                    self._str = f"Standard library module {module_name!r} was not found"
+                message = MISSING_STDLIB_MODULE_MESSAGES.get(
+                    module_name,
+                    f"Standard library module {module_name!r} was not found"
+                )
+                self._str = message
             elif sys.flags.no_site:
                 self._str += (". Site initialization is disabled, did you forget to "
                     + "add the site-packages directory to sys.path "

Makefile.pre.in

@@ -1602,9 +1602,9 @@ sharedmods: $(SHAREDMODS) pybuilddir.txt
 .PHONY: checksharedmods
 checksharedmods: sharedmods $(PYTHON_FOR_BUILD_DEPS) $(BUILDPYTHON)
 	@if [ -n "@MISSING_STDLIB_CONFIG@" ]; then \
-		$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/Tools/build/check_extension_modules.py --generate-stdlib-info="@MISSING_STDLIB_CONFIG@"; \
+		$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/Tools/build/check_extension_modules.py --generate-missing-stdlib-info --with-missing-stdlib-config="@MISSING_STDLIB_CONFIG@"; \
 	else \
-		$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/Tools/build/check_extension_modules.py --generate-stdlib-info; \
+		$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/Tools/build/check_extension_modules.py --generate-missing-stdlib-info; \
 	fi
 	@$(RUNSHARED) $(PYTHON_FOR_BUILD) $(srcdir)/Tools/build/check_extension_modules.py
 

Tools/build/check_extension_modules.py

@@ -27,6 +27,7 @@
 import logging
 import os
 import pathlib
+import pprint
 import re
 import sys
 import sysconfig
@@ -118,10 +119,15 @@
 )
 
 parser.add_argument(
-    "--generate-stdlib-info",
-    nargs="?",
-    const=True,
-    help="Generate file with stdlib module info, with optional config file",
+    "--generate-missing-stdlib-info",
+    action="store_true",
+    help="Generate file with stdlib module info",
+)
+
+parser.add_argument(
+    "--with-missing-stdlib-config",
+    metavar="CONFIG_FILE",
+    help="Path to JSON config file with custom missing module messages",
 )
 
 
@@ -289,14 +295,14 @@ def list_module_names(self, *, all: bool = False) -> set[str]:
             names.update(WINDOWS_MODULES)
         return names
 
-    def generate_stdlib_info(self, config_path: str | None = None) -> None:
+    def generate_missing_stdlib_info(self, config_path: str | None = None) -> None:
         config_messages = {}
         if config_path:
             try:
                 with open(config_path, encoding='utf-8') as f:
                     config_messages = json.load(f)
             except (FileNotFoundError, json.JSONDecodeError) as e:
-                logger.error("Failed to load distributor config %s: %s", config_path, e)
+                raise RuntimeError("Failed to load missing stdlib config %s: %s", config_path, e)
 
         messages = {}
         for name in WINDOWS_MODULES:
@@ -313,11 +319,12 @@ def generate_stdlib_info(self, config_path: str | None = None) -> None:
         content = f'''\
 # Standard library information used by the traceback module for more informative
 # ModuleNotFound error messages.
+# Generated by check_extension_modules.py
 
-MISSING_STDLIB_MODULE_MESSAGES = {messages!r}
+MISSING_STDLIB_MODULE_MESSAGES = {pprint.pformat(messages)}
 '''
 
-        output_path = self.builddir / "_stdlib_modules_info.py"
+        output_path = self.builddir / "_missing_stdlib_module_info.py"
         with open(output_path, "w", encoding="utf-8") as f:
             f.write(content)
 
@@ -539,10 +546,9 @@ def main() -> None:
         names = checker.list_module_names(all=True)
         for name in sorted(names):
             print(name)
-    elif args.generate_stdlib_info:
+    elif args.generate_missing_stdlib_info:
         checker.check()
-        config_path = None if args.generate_stdlib_info is True else args.generate_stdlib_info
-        checker.generate_stdlib_info(config_path)
+        checker.generate_missing_stdlib_info(args.with_missing_stdlib_config)
     else:
         checker.check()
         checker.summary(verbose=args.verbose)