From cc3492e45931d59666508ce81748dcdaa8ac436e Mon Sep 17 00:00:00 2001
From: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
Date: Sat, 22 Jun 2024 12:38:30 -0700
Subject: [PATCH] Fix error reporting on cached run after uninstallation of
 third party library (#17420)

Fixes https://github.com/python/mypy/issues/16766, fixes
https://github.com/python/mypy/issues/17049
---
 mypy/build.py                         |  7 +++++--
 mypy/errors.py                        |  2 +-
 test-data/unit/check-incremental.test | 15 +++++++++++++++
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/mypy/build.py b/mypy/build.py
index 3ceb473f0948..733f0685792e 100644
--- a/mypy/build.py
+++ b/mypy/build.py
@@ -3467,8 +3467,11 @@ 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:
-        errors = manager.errors.file_messages(graph[id].xpath, formatter=manager.error_formatter)
-        manager.flush_errors(manager.errors.simplify_path(graph[id].xpath), errors, False)
+        if graph[id].xpath not in manager.errors.ignored_files:
+            errors = manager.errors.file_messages(
+                graph[id].xpath, formatter=manager.error_formatter
+            )
+            manager.flush_errors(manager.errors.simplify_path(graph[id].xpath), errors, False)
         graph[id].write_cache()
         graph[id].mark_as_rechecked()
 
diff --git a/mypy/errors.py b/mypy/errors.py
index 7a937da39c20..d6dcd4e49e13 100644
--- a/mypy/errors.py
+++ b/mypy/errors.py
@@ -803,7 +803,7 @@ 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?
diff --git a/test-data/unit/check-incremental.test b/test-data/unit/check-incremental.test
index ead896b8e458..24292bce3e21 100644
--- a/test-data/unit/check-incremental.test
+++ b/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]