gh-139707: Add mechanism for distributors to supply error messages for missing stdlib modules (GH-140783)

Tools/build/check_extension_modules.py

@@ -23,9 +23,11 @@
 import _imp
 import argparse
 import enum
+import json
 import logging
 import os
 import pathlib
+import pprint
 import re
 import sys
 import sysconfig
@@ -116,6 +118,18 @@
     help="Print a list of module names to stdout and exit",
 )
 
+parser.add_argument(
+    "--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",
+)
+
 
 @enum.unique
 class ModuleState(enum.Enum):
@@ -281,6 +295,39 @@ def list_module_names(self, *, all: bool = False) -> set[str]:
             names.update(WINDOWS_MODULES)
         return names
 
+    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:
+                raise RuntimeError(f"Failed to load missing stdlib config {config_path!r}") from e
+
+        messages = {}
+        for name in WINDOWS_MODULES:
+            messages[name] = f"Unsupported platform for Windows-only standard library module {name!r}"
+
+        for modinfo in self.modules:
+            if modinfo.state in (ModuleState.DISABLED, ModuleState.DISABLED_SETUP):
+                messages[modinfo.name] = f"Standard library module disabled during build {modinfo.name!r} was not found"
+            elif modinfo.state == ModuleState.NA:
+                messages[modinfo.name] = f"Unsupported platform for standard library module {modinfo.name!r}"
+
+        messages.update(config_messages)
+
+        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 = {pprint.pformat(messages)}
+'''
+
+        output_path = self.builddir / "_missing_stdlib_info.py"
+        with open(output_path, "w", encoding="utf-8") as f:
+            f.write(content)
+
     def get_builddir(self) -> pathlib.Path:
         try:
             with open(self.pybuilddir_txt, encoding="utf-8") as f:
@@ -499,6 +546,9 @@ def main() -> None:
         names = checker.list_module_names(all=True)
         for name in sorted(names):
             print(name)
+    elif args.generate_missing_stdlib_info:
+        checker.check()
+        checker.generate_missing_stdlib_info(args.with_missing_stdlib_config)
     else:
         checker.check()
         checker.summary(verbose=args.verbose)