fix(changelog_formats): raise on explicit invalid format even with valid filename

Refactor get_changelog_format with explicit branching: when changelog_format is set, look it up directly and raise ChangelogFormatUnknown if missing, regardless of whether the filename extension is recognized. Previously the 'or _guess_changelog_format' fallback could silently ignore an invalid explicit configuration when the filename had a known extension.

Add a regression test exercising changelog_format='invalidformat' with filename='CHANGELOG.md'.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: bearomorphism

commitizen/changelog_formats/__init__.py

@@ -72,23 +72,25 @@ def get_changelog_format(
         be matched to a known format and no ``changelog_format`` is set.
     """
     name: str | None = config.settings.get("changelog_format")
-    format = (
-        name and KNOWN_CHANGELOG_FORMATS.get(name) or _guess_changelog_format(filename)
-    )
+    known = ", ".join(sorted(KNOWN_CHANGELOG_FORMATS)) or "(none registered)"
 
-    if not format:
-        known = ", ".join(sorted(KNOWN_CHANGELOG_FORMATS)) or "(none registered)"
-        if name:
+    if name:
+        format_cls = KNOWN_CHANGELOG_FORMATS.get(name)
+        if format_cls is None:
             raise ChangelogFormatUnknown(
                 f"Unknown changelog format '{name}'. Known formats: {known}."
             )
+        return format_cls(config)
+
+    format_cls = _guess_changelog_format(filename)
+    if format_cls is None:
         raise ChangelogFormatUnknown(
             "Cannot infer changelog format from filename "
             f"'{filename}'. Set the `changelog_format` setting "
             f"explicitly. Known formats: {known}."
         )
 
-    return format(config)
+    return format_cls(config)
 
 
 def _guess_changelog_format(filename: str | None) -> type[ChangelogFormat] | None:

tests/test_changelog_formats.py

@@ -83,3 +83,12 @@ def test_get_format_unknown_name_lists_known_formats(config: BaseConfig):
     msg = str(excinfo.value)
     assert "definitely-not-a-format" in msg
     assert "Known formats" in msg
+
+
+def test_get_format_unknown_name_with_known_filename_raises(config: BaseConfig):
+    config.settings["changelog_format"] = "invalidformat"
+    with pytest.raises(ChangelogFormatUnknown) as excinfo:
+        get_changelog_format(config, "CHANGELOG.md")
+    msg = str(excinfo.value)
+    assert "invalidformat" in msg
+    assert "Known formats" in msg