Fix integration between stdin filename and --force-exclude (#4539)

CHANGES.md

@@ -56,6 +56,9 @@
 
 <!-- For example, Docker, GitHub Actions, pre-commit, editors -->
 
+- If using stdin with `--stdin-filename` set to a force excluded path, stdin won't be
+  formatted. (#4539)
+
 ### Documentation
 
 <!-- Major changes to documentation and policies. Small docs changes

src/black/__init__.py

@@ -749,6 +749,12 @@ def get_sources(
     for s in src:
         if s == "-" and stdin_filename:
             path = Path(stdin_filename)
+            if path_is_excluded(stdin_filename, force_exclude):
+                report.path_ignored(
+                    path,
+                    "--stdin-filename matches the --force-exclude regular expression",
+                )
+                continue
             is_stdin = True
         else:
             path = Path(s)