Remove file_exists parameter from mypy.parse.parse() calls

python · bzoracler · Apr 17, 2026 · Apr 17, 2026 · Apr 17, 2026 · Apr 17, 2026
commit eca912fbeba03008ae283ac5dcee22f519109330
diff --git a/misc/dump-ast.py b/misc/dump-ast.py
@@ -19,7 +19,7 @@ def dump(fname: str, python_version: tuple[int, int], quiet: bool = False) -> No
     options.python_version = python_version
     with open(fname, "rb") as f:
         s = f.read()
-        tree = parse(s, fname, None, errors=Errors(options), options=options, file_exists=True)
+        tree = parse(s, fname, None, errors=Errors(options), options=options)
         if not quiet:
             print(tree)
 

diff --git a/mypy/build.py b/mypy/build.py
@@ -1214,9 +1214,7 @@ def parse_file(
         Raise CompileError if there is a parse error.
         """
         imports_only = False
-        file_exists = self.fscache.exists(path)
-        if self.workers and file_exists:
-            # Currently, we can use the native parser only for actual files.
+        if self.workers:
             imports_only = True
         t0 = time.time()
         parse_errors: list[ParseError] = []
@@ -1230,7 +1228,6 @@ def parse_file(
                 id,
                 self.errors,
                 options=options,
-                file_exists=file_exists,
                 imports_only=imports_only,
             )
         tree._fullname = id

diff --git a/mypy/checkstrformat.py b/mypy/checkstrformat.py
@@ -587,7 +587,6 @@ def apply_field_accessors(
             module=None,
             options=self.chk.options,
             errors=temp_errors,
-            file_exists=False,
         )
         if temp_errors.is_errors():
             self.msg.fail(

diff --git a/mypy/parse.py b/mypy/parse.py
@@ -17,7 +17,6 @@ def parse(
     module: str | None,
     errors: Errors,
     options: Options,
-    file_exists: bool,
     imports_only: bool = False,
 ) -> tuple[MypyFile, list[ParseError]]:
     """Parse a source file, without doing any semantic analysis.
@@ -28,27 +27,25 @@ def parse(
     The python_version (major, minor) option determines the Python syntax variant.
     """
     if options.native_parser:
-        # Native parser only works with actual files on disk
-        # Fall back to fastparse for in-memory source or non-existent files
-        if file_exists:
-            import mypy.nativeparse
-
-            ignore_errors = options.ignore_errors or fnam in errors.ignored_files
-            # If errors are ignored, we can drop many function bodies to speed up type checking.
-            strip_function_bodies = ignore_errors and not options.preserve_asts
-            tree, parse_errors, type_ignores = mypy.nativeparse.native_parse(
-                fnam,
-                options,
-                skip_function_bodies=strip_function_bodies,
-                imports_only=imports_only,
-            )
-            # Convert type ignores list to dict
-            tree.ignored_lines = dict(type_ignores)
-            # Set is_stub based on file extension
-            tree.is_stub = fnam.endswith(".pyi")
-            # Note: tree.imports is populated directly by native_parse with deserialized
-            # import metadata, so we don't need to collect imports via AST traversal
-            return tree, parse_errors
+        import mypy.nativeparse
+
+        ignore_errors = options.ignore_errors or fnam in errors.ignored_files
+        # If errors are ignored, we can drop many function bodies to speed up type checking.
+        strip_function_bodies = ignore_errors and not options.preserve_asts
+        tree, parse_errors, type_ignores = mypy.nativeparse.native_parse(
+            fnam,
+            options,
+            source,
+            skip_function_bodies=strip_function_bodies,
+            imports_only=imports_only,
+        )
+        # Convert type ignores list to dict
+        tree.ignored_lines = dict(type_ignores)
+        # Set is_stub based on file extension
+        tree.is_stub = fnam.endswith(".pyi")
+        # Note: tree.imports is populated directly by native_parse with deserialized
+        # import metadata, so we don't need to collect imports via AST traversal
+        return tree, parse_errors
         # Fall through to fastparse for non-existent files
 
     assert not imports_only

diff --git a/mypy/stubgen.py b/mypy/stubgen.py
@@ -1750,7 +1750,6 @@ def parse_source_file(mod: StubSource, mypy_options: MypyOptions) -> None:
         module=mod.module,
         errors=errors,
         options=mypy_options,
-        file_exists=True,
     )
     mod.ast._fullname = mod.module
     for err in errs:

diff --git a/mypy/test/testparse.py b/mypy/test/testparse.py
@@ -66,7 +66,6 @@ def test_parser(testcase: DataDrivenTestCase) -> None:
             module="__main__",
             errors=errors,
             options=options,
-            file_exists=False,
         )
         if errors.is_errors():
             errors.raise_error()
@@ -107,7 +106,6 @@ def test_parse_error(testcase: DataDrivenTestCase) -> None:
             "__main__",
             errors=errors,
             options=options,
-            file_exists=False,
         )
         if errors.is_errors():
             errors.raise_error()