Allow override of lexer in Syntax.from_path

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Workaround for edge case of object from Faiss with no `__class__` https://github.com/Textualize/rich/issues/1838
 - Add `Syntax.guess_lexer`, add support for more lexers (e.g. Django templates etc.) https://github.com/Textualize/rich/pull/1869
+- Add `lexer` parameter to `Syntax.from_path` to allow for overrides https://github.com/Textualize/rich/pull/1873
 - Ensure `Syntax` always justifies left https://github.com/Textualize/rich/pull/1872
 
 

rich/syntax.py

@@ -266,6 +266,7 @@ def from_path(
         cls,
         path: str,
         encoding: str = "utf-8",
+        lexer: Optional[Union[Lexer, str]] = None,
         theme: Union[str, SyntaxTheme] = DEFAULT_THEME,
         dedent: bool = False,
         line_numbers: bool = False,
@@ -283,6 +284,7 @@ def from_path(
         Args:
             path (str): Path to file to highlight.
             encoding (str): Encoding of file.
+            lexer (str | Lexer, optional): Lexer to use. If None, lexer will be auto-detected from path/file content.
             theme (str, optional): Color theme, aka Pygments style (see https://pygments.org/docs/styles/#getting-a-list-of-available-styles). Defaults to "emacs".
             dedent (bool, optional): Enable stripping of initial whitespace. Defaults to True.
             line_numbers (bool, optional): Enable rendering of line numbers. Defaults to False.
@@ -301,11 +303,12 @@ def from_path(
         with open(path, "rt", encoding=encoding) as code_file:
             code = code_file.read()
 
-        lexer_name = cls.guess_lexer(path, code=code)
+        if not lexer:
+            lexer = cls.guess_lexer(path, code=code)
 
         return cls(
             code,
-            lexer_name,
+            lexer,
             theme=theme,
             dedent=dedent,
             line_numbers=line_numbers,
@@ -756,6 +759,7 @@ def __rich_console__(
     else:
         syntax = Syntax.from_path(
             args.path,
+            lexer=args.lexer_name,
             line_numbers=args.line_numbers,
             word_wrap=args.word_wrap,
             theme=args.theme,

tests/test_syntax.py

@@ -241,8 +241,13 @@ def test_ansi_theme():
     assert theme.get_background_style() == Style()
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="permissions error on Windows")
-def test_from_file():
+skip_windows_permission_error = pytest.mark.skipif(
+    sys.platform == "win32", reason="permissions error on Windows"
+)
+
+
+@skip_windows_permission_error
+def test_from_path():
     fh, path = tempfile.mkstemp("example.py")
     try:
         os.write(fh, b"import this\n")
@@ -254,8 +259,8 @@ def test_from_file():
         os.remove(path)
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="permissions error on Windows")
-def test_from_file_unknown_lexer():
+@skip_windows_permission_error
+def test_from_path_unknown_lexer():
     fh, path = tempfile.mkstemp("example.nosuchtype")
     try:
         os.write(fh, b"import this\n")
@@ -266,6 +271,30 @@ def test_from_file_unknown_lexer():
         os.remove(path)
 
 
+@skip_windows_permission_error
+def test_from_path_lexer_override():
+    fh, path = tempfile.mkstemp("example.nosuchtype")
+    try:
+        os.write(fh, b"import this\n")
+        syntax = Syntax.from_path(path, lexer="rust")
+        assert syntax.lexer.name is "Rust"
+        assert syntax.code == "import this\n"
+    finally:
+        os.remove(path)
+
+
+@skip_windows_permission_error
+def test_from_path_lexer_override_invalid_lexer():
+    fh, path = tempfile.mkstemp("example.nosuchtype")
+    try:
+        os.write(fh, b"import this\n")
+        syntax = Syntax.from_path(path, lexer="blah")
+        assert syntax.lexer is None
+        assert syntax.code == "import this\n"
+    finally:
+        os.remove(path)
+
+
 def test_syntax_guess_lexer():
     assert Syntax.guess_lexer("banana.py") == "python"
     assert Syntax.guess_lexer("banana.py", "import this") == "python"