Fix error reporting on cached run after uninstallation of third party library (python#17420)

Fixes python#16766, fixes
python#17049

Author: hauntsaninja

mypy/build.py

@@ -3459,11 +3459,12 @@ def process_stale_scc(graph: Graph, scc: list[str], manager: BuildManager) -> No
         for id in stale:
             graph[id].transitive_error = True
     for id in stale:
-        manager.flush_errors(
-            manager.errors.simplify_path(graph[id].xpath),
-            manager.errors.file_messages(graph[id].xpath),
-            False,
-        )
+        if graph[id].xpath not in manager.errors.ignored_files:
+            manager.flush_errors(
+                manager.errors.simplify_path(graph[id].xpath),
+                manager.errors.file_messages(graph[id].xpath),
+                False,
+            )
         graph[id].write_cache()
         graph[id].mark_as_rechecked()
 

mypy/errors.py

@@ -802,7 +802,7 @@ def blocker_module(self) -> str | None:
 
     def is_errors_for_file(self, file: str) -> bool:
         """Are there any errors for the given file?"""
-        return file in self.error_info_map
+        return file in self.error_info_map and file not in self.ignored_files
 
     def prefer_simple_messages(self) -> bool:
         """Should we generate simple/fast error messages?

test-data/unit/check-incremental.test

@@ -1833,6 +1833,21 @@ main:3: note: Revealed type is "builtins.int"
 main:3: note: Revealed type is "Any"
 
 
+[case testIncrementalIgnoreErrors]
+# flags: --config-file tmp/mypy.ini
+import a
+[file a.py]
+import module_that_will_be_deleted
+[file module_that_will_be_deleted.py]
+
+[file mypy.ini]
+\[mypy]
+\[mypy-a]
+ignore_errors = True
+[delete module_that_will_be_deleted.py.2]
+[out1]
+[out2]
+
 [case testIncrementalNamedTupleInMethod]
 from ntcrash import nope
 [file ntcrash.py]