Clear warnings for each file in codemod cli

libcst/codemod/_cli.py

@@ -22,6 +22,7 @@
 
 from libcst import parse_module, PartialParserConfig
 from libcst.codemod._codemod import Codemod
+from libcst.codemod._context import CodemodContext
 from libcst.codemod._dummy_pool import DummyPool
 from libcst.codemod._runner import (
     SkipFile,
@@ -246,30 +247,28 @@
                 ),
             )
 
-        # Somewhat gross hack to provide the filename in the transform's context.
-        # We do this after the fork so that a context that was initialized with
-        # some defaults before calling parallel_exec_transform_with_prettyprint
-        # will be updated per-file.
-        transformer.context = replace(
-            transformer.context,
-            filename=filename,
-            scratch=deepcopy(scratch),
-        )
-
         # determine the module and package name for this file
         try:
             module_name_and_package = calculate_module_and_package(
                 config.repo_root or ".", filename
             )
-            transformer.context = replace(
-                transformer.context,
-                full_module_name=module_name_and_package.name,
-                full_package_name=module_name_and_package.package,
-            )
+            mod_name = module_name_and_package.name
+            pkg_name = module_name_and_package.package
         except ValueError as ex:
             print(
                 f"Failed to determine module name for {filename}: {ex}", file=sys.stderr
             )
+            mod_name = None
+            pkg_name = None
+
+        # Apart from metadata_manager, every field of context should be reset per file
+        transformer.context = CodemodContext(
+            scratch=deepcopy(scratch),
+            filename=filename,
+            full_module_name=mod_name,
+            full_package_name=pkg_name,
+            metadata_manager=transformer.context.metadata_manager,
+        )
 
         # Run the transform, bail if we failed or if we aren't formatting code
         try:
@@ -420,7 +419,7 @@
         operations still to do.
         """
 
-        if files_finished <= 0:
+        if files_finished <= 0 or elapsed_seconds == 0:
             # Technically infinite but calculating sounds better.
             return "[calculating]"
 

libcst/codemod/tests/test_codemod_cli.py

@@ -8,10 +8,12 @@
 import platform
 import subprocess
 import sys
+import tempfile
 from pathlib import Path
 from unittest import skipIf
 
 from libcst._parser.entrypoints import is_native
+from libcst.codemod import CodemodTest
 from libcst.testing.utils import UnitTest
 
 
@@ -63,3 +65,31 @@ def test_codemod_external(self) -> None:
             stderr=subprocess.STDOUT,
         )
         assert "Finished codemodding 1 files!" in output
+
+    def test_warning_messages_several_files(self) -> None:
+        code = """
+        def baz() -> str:
+            return "{}: {}".format(*baz)
+        """
+        with tempfile.TemporaryDirectory() as tmpdir:
+            p = Path(tmpdir)
+            (p / "mod1.py").write_text(CodemodTest.make_fixture_data(code))
+            (p / "mod2.py").write_text(CodemodTest.make_fixture_data(code))
+            (p / "mod3.py").write_text(CodemodTest.make_fixture_data(code))
+            output = subprocess.run(
+                [
+                    sys.executable,
+                    "-m",
+                    "libcst.tool",
+                    "codemod",
+                    "convert_format_to_fstring.ConvertFormatStringCommand",
+                    str(p),
+                ],
+                encoding="utf-8",
+                stderr=subprocess.PIPE,
+            )
+            # Each module will generate a warning, so we should get 3 warnings in total
+            self.assertIn(
+                "- 3 warnings were generated.",
+                output.stderr,
+            )