Ensure errors persist after file change

Before this change, when a module was changed, some errors would not
re-appear.

This change ensures that unused-ignore and ignore-without-code errors
are maintained when a module is re-analyzed after it changes.

We use Python to print a newline to the end of the file, which doesn't
run afoul of issues with newlines on Windows, unlike `echo`.

Co-authored-by: AlexWaygood <[email protected]>

Author: meshy

mypy/server/update.py

@@ -667,6 +667,8 @@ def restore(ids: list[str]) -> None:
     state.type_check_first_pass()
     state.type_check_second_pass()
     state.detect_possibly_undefined_vars()
+    state.generate_unused_ignore_notes()
+    state.generate_ignore_without_code_notes()
     t2 = time.time()
     state.finish_passes()
     t3 = time.time()

test-data/unit/daemon.test

@@ -564,7 +564,7 @@ Daemon started
 $ dmypy check -- bar.py
 bar.py:2: error: Unused "type: ignore" comment
 == Return code: 1
-$ echo '' >> bar.py
+$ {python} -c "print('\n')" >> bar.py
 $ dmypy check -- bar.py
 bar.py:2: error: Unused "type: ignore" comment
 == Return code: 1
@@ -582,7 +582,7 @@ Daemon started
 $ dmypy check -- bar.py
 bar.py:2: error: "type: ignore" comment without error code  [ignore-without-code]
 == Return code: 1
-$ echo '' >> bar.py
+$ {python} -c "print('\n')" >> bar.py
 $ dmypy check -- bar.py
 bar.py:2: error: "type: ignore" comment without error code  [ignore-without-code]
 == Return code: 1