Ensure wholly ignored files don't get errors about missing codes

Author: PeterJCLaw

mypy/errorcodes.py

@@ -138,5 +138,10 @@ def __str__(self) -> str:
 # Syntax errors are often blocking.
 SYNTAX: Final = ErrorCode("syntax", "Report syntax errors", "General")
 
+# This is an internal marker code for a whole-file ignore. It is not intended to
+# be user-visible.
+FILE: Final = ErrorCode("file", "Internal marker for a whole file being ignored", "General")
+del error_codes[FILE.code]
+
 # This is a catch-all for remaining uncategorized errors.
 MISC: Final = ErrorCode("misc", "Miscellaneous other checks", "General")

mypy/errors.py

@@ -492,6 +492,13 @@ def generate_ignore_without_code_errors(self,
             return
 
         used_ignored_lines = self.used_ignored_lines[file]
+
+        # If the whole file is ignored, ignore it.
+        if used_ignored_lines:
+            _, used_codes = min(used_ignored_lines.items())
+            if codes.FILE.code in used_codes:
+                return
+
         for line, ignored_codes in self.ignored_lines[file].items():
             if ignored_codes:
                 continue

mypy/fastparse.py

@@ -360,7 +360,7 @@ def translate_stmt_list(self,
         if (ismodule and stmts and self.type_ignores
                 and min(self.type_ignores) < self.get_lineno(stmts[0])):
             self.errors.used_ignored_lines[self.errors.file][min(self.type_ignores)].append(
-                codes.MISC.code)
+                codes.FILE.code)
             block = Block(self.fix_function_overloads(self.translate_stmt_list(stmts)))
             mark_block_unreachable(block)
             return [block]

mypy/fastparse2.py

@@ -216,7 +216,7 @@ def translate_stmt_list(self,
         if (module and stmts and self.type_ignores
                 and min(self.type_ignores) < self.get_lineno(stmts[0])):
             self.errors.used_ignored_lines[self.errors.file][min(self.type_ignores)].append(
-                codes.MISC.code)
+                codes.FILE.code)
             block = Block(self.fix_function_overloads(self.translate_stmt_list(stmts)))
             mark_block_unreachable(block)
             return [block]

test-data/unit/check-errorcodes.test

@@ -144,6 +144,12 @@ y # type: ignore # E: "type: ignore" comment without error code
 # flags: --disallow-ignore-without-code --warn-unused-ignores
 "x" # type: ignore # E: Unused "type: ignore" comment
 
+[case testErrorCodeMissingWholeFileIgnores]
+# flags: --disallow-ignore-without-code
+# type: ignore  # whole file ignore
+x
+y # type: ignore  # ignore the lack of error code since we're ignore the whole file
+
 [case testErrorCodeIgnoreWithExtraSpace]
 x  # type: ignore   [name-defined]
 x2 # type: ignore   [ name-defined ]