Petr's review

Author: StanFromIreland

Doc/using/configure.rst

@@ -265,11 +265,14 @@ General Options
    modules that are packaged separately.
 
    The JSON file should map missing module names to custom error message strings.
-   For example, a configuration for the :mod:`tkinter` module:
+   For example, if your distribution packages :mod:`tkinter` and
+   :mod:`_tkinter` separately and excludes :mod:`_gdbm` for legal reasons,
+   the configuration could contain:
 
    .. code-block:: json
 
       {
+          "_gdbm": "The '_gdbm' module is not available in this distribution"
           "tkinter": "Install the python-tk package to use tkinter",
           "_tkinter": "Install the python-tk package to use tkinter",
       }

Lib/test/test_traceback.py

@@ -5072,6 +5072,16 @@ def test_missing_stdlib_module(self):
 
         self.assertIn(b"Install 'spam4life' for 'spam'", stderr)
 
+    @unittest.skipIf(sys.platform == "win32", "Non-Windows test")
+    def test_windows_only_module_error(self):
+        try:
+            import msvcrt  # noqa: F401
+        except ModuleNotFoundError:
+            formatted = traceback.format_exc()
+            self.assertIn("Unsupported platform for Windows-only standard library module 'msvcrt'", formatted)
+        else:
+            self.fail("ModuleNotFoundError was not raised")
+
 
 class TestColorizedTraceback(unittest.TestCase):
     maxDiff = None

Lib/traceback.py

@@ -1118,11 +1118,11 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
                 if MISSING_STDLIB_MODULE_MESSAGES is not None:
                     message = MISSING_STDLIB_MODULE_MESSAGES.get(
                         module_name,
-                        f"Standard library module '{module_name}' was not found"
+                        f"Standard library module {module_name!r} was not found"
                     )
                     self._str = message
                 else:
-                    self._str = f"Standard library module '{module_name}' was not found"
+                    self._str = f"Standard library module {module_name!r} was not found"
             elif sys.flags.no_site:
                 self._str += (". Site initialization is disabled, did you forget to "
                     + "add the site-packages directory to sys.path "

Tools/build/check_extension_modules.py

@@ -290,14 +290,6 @@ def list_module_names(self, *, all: bool = False) -> set[str]:
         return names
 
     def generate_stdlib_info(self, config_path: str | None = None) -> None:
-
-        disabled_modules = {modinfo.name for modinfo in self.modules
-                           if modinfo.state in (ModuleState.DISABLED, ModuleState.DISABLED_SETUP)}
-        missing_modules = {modinfo.name for modinfo in self.modules
-                          if modinfo.state == ModuleState.MISSING}
-        na_modules = {modinfo.name for modinfo in self.modules
-                     if modinfo.state == ModuleState.NA}
-
         config_messages = {}
         if config_path:
             try:
@@ -306,26 +298,22 @@ def generate_stdlib_info(self, config_path: str | None = None) -> None:
             except (FileNotFoundError, json.JSONDecodeError) as e:
                 logger.error("Failed to load distributor config %s: %s", config_path, e)
 
-        default_messages = {
-            **{name: f"Windows-only standard library module '{name}' was not found"
-               for name in WINDOWS_MODULES},
-            **{name: f"Standard library module disabled during build '{name}' was not found"
-               for name in disabled_modules},
-            **{name: f"Unsupported platform for standard library module '{name}'"
-               for name in na_modules},
-        }
+        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 = {**default_messages, **config_messages}
+        messages.update(config_messages)
 
         content = f'''\
 # Standard library information used by the traceback module for more informative
 # ModuleNotFound error messages.
 
-DISABLED_MODULES = {sorted(disabled_modules)!r}
-MISSING_MODULES = {sorted(missing_modules)!r}
-NOT_AVAILABLE_MODULES = {sorted(na_modules)!r}
-WINDOWS_ONLY_MODULES = {sorted(WINDOWS_MODULES)!r}
-
 MISSING_STDLIB_MODULE_MESSAGES = {messages!r}
 '''