Respect file config comments for stale modules

Author: Adam Turner

mypy/build.py

@@ -4769,13 +4769,13 @@ def process_stale_scc(graph: Graph, ascc: SCC, manager: BuildManager) -> None:
 
     t2 = time.time()
     stale = scc
+    # Parse before verify_dependencies so that inline config comments
+    # (e.g. "# mypy: disable-error-code") are applied to options.
+    manager.parse_all([graph[id] for id in stale], post_parse=False)
     for id in stale:
         # Re-generate import errors in case this module was loaded from the cache.
         if graph[id].meta:
             graph[id].verify_dependencies(suppressed_only=True)
-    # We may already have parsed the modules, or not.
-    # If the former, parse_file() is a no-op.
-    manager.parse_all([graph[id] for id in stale], post_parse=False)
     if "typing" in scc:
         # For historical reasons we need to manually add typing aliases
         # for built-in generic collections, see docstring of

test-data/unit/check-incremental.test

@@ -7995,3 +7995,19 @@ import mod
 [out2]
 main:2: error: Cannot find implementation or library stub for module named "mod"
 main:2: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
+
+[case testIncrementalFileConfigCommentsStale]
+-- When a dependency changes, the importing module becomes stale and is
+-- reprocessed via process_stale_scc. As inline config comments are not cached
+-- (by design), moving the order of processing the stale SCC can accidentally
+-- break file config comments on subsequent runs.
+# mypy: disable-error-code="import-not-found"
+import nonexistent
+import b
+[file b.py]
+x = 1
+[file b.py.2]
+x = "hello"
+[builtins fixtures/module.pyi]
+[stale b]
+[rechecked b]