gh-136507: Fix mimetypes CLI cannot handle multiple file parameters

Lib/mimetypes.py

@@ -717,25 +717,29 @@ def _parse_args(args):
 
 
 def _main(args=None):
-    """Run the mimetypes command-line interface and return a text to print."""
+    """Run the mimetypes command-line interface."""
     import sys
 
     args, help_text = _parse_args(args)
+    if not args.type:
+        print(help_text)
+        return
 
     if args.extension:
         for gtype in args.type:
             guess = guess_extension(gtype, not args.lenient)
             if guess:
-                return str(guess)
-            sys.exit(f"error: unknown type {gtype}")
+                print(str(guess))
+            else:
+                print(f"error: unknown type {gtype}", file=sys.stderr)
     else:
         for gtype in args.type:
             guess, encoding = guess_type(gtype, not args.lenient)
             if guess:
-                return f"type: {guess} encoding: {encoding}"
-            sys.exit(f"error: media type unknown for {gtype}")
-    return help_text
+                print(f"type: {guess} encoding: {encoding}")
+            else:
+                print(f"error: media type unknown for {gtype}", file=sys.stderr)
 
 
 if __name__ == '__main__':
-    print(_main())
+    _main()

Lib/test/test_mimetypes.py

@@ -1,3 +1,4 @@
+import contextlib
 import io
 import mimetypes
 import os
@@ -476,16 +477,22 @@ def test_invocation(self):
             ("-e image/jpeg", ".jpg"),
             ("-l foo.webp", "type: image/webp encoding: None"),
         ]:
-            self.assertEqual(mimetypes._main(shlex.split(command)), expected)
+            with self.subTest(command=command):
+                out = io.StringIO()
+                with contextlib.redirect_stdout(out):
+                    mimetypes._main(shlex.split(command))
+                self.assertEqual(out.getvalue().strip(), expected)
 
     def test_invocation_error(self):
         for command, expected in [
             ("-e image/jpg", "error: unknown type image/jpg"),
             ("foo.bar_ext", "error: media type unknown for foo.bar_ext"),
         ]:
             with self.subTest(command=command):
-                with self.assertRaisesRegex(SystemExit, expected):
+                err = io.StringIO()
+                with contextlib.redirect_stderr(err):
                     mimetypes._main(shlex.split(command))
+                self.assertIn(expected, err.getvalue().strip())
 
 
 if __name__ == "__main__":

Misc/NEWS.d/next/Library/2025-07-10-21-02-43.gh-issue-136507.pnEuGS.rst

@@ -0,0 +1 @@
+Fix mimetypes CLI cannot handle multiple file parameters