Add enable_incomplete_feature validation to stubtest (#17635)

Closes #17634
Refs #17628 
Refs #17629

mypy/main.py

@@ -23,7 +23,7 @@
 from mypy.find_sources import InvalidSourceList, create_source_list
 from mypy.fscache import FileSystemCache
 from mypy.modulefinder import BuildSource, FindModuleCache, SearchPaths, get_search_dirs, mypy_path
-from mypy.options import COMPLETE_FEATURES, INCOMPLETE_FEATURES, BuildType, Options
+from mypy.options import INCOMPLETE_FEATURES, BuildType, Options
 from mypy.split_namespace import SplitNamespace
 from mypy.version import __version__
 
@@ -1336,13 +1336,7 @@ def set_strict_flags() -> None:
     validate_package_allow_list(options.untyped_calls_exclude)
 
     options.process_error_codes(error_callback=parser.error)
-
-    # Validate incomplete features.
-    for feature in options.enable_incomplete_feature:
-        if feature not in INCOMPLETE_FEATURES | COMPLETE_FEATURES:
-            parser.error(f"Unknown incomplete feature: {feature}")
-        if feature in COMPLETE_FEATURES:
-            print(f"Warning: {feature} is already enabled by default")
+    options.process_incomplete_features(error_callback=parser.error, warning_callback=print)
 
     # Compute absolute path for custom typeshed (if present).
     if options.custom_typeshed_dir is not None:

mypy/options.py

@@ -433,6 +433,16 @@ def process_error_codes(self, *, error_callback: Callable[[str], Any]) -> None:
         # Enabling an error code always overrides disabling
         self.disabled_error_codes -= self.enabled_error_codes
 
+    def process_incomplete_features(
+        self, *, error_callback: Callable[[str], Any], warning_callback: Callable[[str], Any]
+    ) -> None:
+        # Validate incomplete features.
+        for feature in self.enable_incomplete_feature:
+            if feature not in INCOMPLETE_FEATURES | COMPLETE_FEATURES:
+                error_callback(f"Unknown incomplete feature: {feature}")
+            if feature in COMPLETE_FEATURES:
+                warning_callback(f"Warning: {feature} is already enabled by default")
+
     def apply_changes(self, changes: dict[str, object]) -> Options:
         # Note: effects of this method *must* be idempotent.
         new_options = Options()

mypy/stubtest.py

@@ -1945,7 +1945,13 @@ def error_callback(msg: str) -> typing.NoReturn:
         print(_style("error:", color="red", bold=True), msg)
         sys.exit(1)
 
+    def warning_callback(msg: str) -> None:
+        print(_style("warning:", color="yellow", bold=True), msg)
+
     options.process_error_codes(error_callback=error_callback)
+    options.process_incomplete_features(
+        error_callback=error_callback, warning_callback=warning_callback
+    )
 
     try:
         modules = build_stubs(modules, options, find_submodules=not args.check_typeshed)

mypy/test/teststubtest.py

@@ -2490,6 +2490,20 @@ def test_config_file_error_codes(self) -> None:
         output = run_stubtest(stub=stub, runtime=runtime, options=[], config_file=config_file)
         assert output == "Success: no issues found in 1 module\n"
 
+    def test_config_file_wrong_incomplete_feature(self) -> None:
+        runtime = "x = 1\n"
+        stub = "x: int\n"
+        config_file = "[mypy]\nenable_incomplete_feature = Unpack\n"
+        output = run_stubtest(stub=stub, runtime=runtime, options=[], config_file=config_file)
+        assert output == (
+            "warning: Warning: Unpack is already enabled by default\n"
+            "Success: no issues found in 1 module\n"
+        )
+
+        config_file = "[mypy]\nenable_incomplete_feature = not-a-valid-name\n"
+        with self.assertRaises(SystemExit):
+            run_stubtest(stub=stub, runtime=runtime, options=[], config_file=config_file)
+
     def test_no_modules(self) -> None:
         output = io.StringIO()
         with contextlib.redirect_stdout(output):