fix colors in log on Windows

CHANGES.rst

@@ -124,6 +124,9 @@ Unreleased
     addresses, instead of ``0.0.0.0`` or ``::``. It also warns about not
     running the development server in production in this case.
     :issue:`1964`
+-   Colors in the development server log are displayed if Colorama is
+    installed on Windows. For all platforms, style support no longer
+    requires Click. :issue:`1832`
 
 
 Version 1.0.2

setup.cfg

@@ -94,6 +94,9 @@ warn_redundant_casts = True
 warn_unused_configs = True
 warn_unused_ignores = True
 
+[mypy-colorama.*]
+ignore_missing_imports = True
+
 [mypy-cryptography.*]
 ignore_missing_imports = True
 

src/werkzeug/_internal.py

@@ -183,6 +183,20 @@ def _has_level_handler(logger: logging.Logger) -> bool:
     return False
 
 
+class _ColorStreamHandler(logging.StreamHandler):
+    """On Windows, wrap stream with Colorama for ANSI style support."""
+
+    def __init__(self):
+        try:
+            import colorama
+        except ImportError:
+            stream = None
+        else:
+            stream = colorama.AnsiToWin32(sys.stderr)
+
+        super().__init__(stream)
+
+
 def _log(type: str, message: str, *args, **kwargs) -> None:
     """Log a message to the 'werkzeug' logger.
 
@@ -200,7 +214,7 @@ def _log(type: str, message: str, *args, **kwargs) -> None:
             _logger.setLevel(logging.INFO)
 
         if not _has_level_handler(_logger):
-            _logger.addHandler(logging.StreamHandler())
+            _logger.addHandler(_ColorStreamHandler())
 
     getattr(_logger, type)(message.rstrip(), *args, **kwargs)
 

src/werkzeug/serving.py

@@ -42,10 +42,13 @@ def __getattr__(self, name):
 
     ssl = _SslDummy()  # type: ignore
 
-try:
-    import click
-except ImportError:
-    click = None  # type: ignore
+_log_add_style = True
+
+if os.name == "nt":
+    try:
+        __import__("colorama")
+    except ImportError:
+        _log_add_style = False
 
 can_fork = hasattr(os, "fork")
 
@@ -392,23 +395,21 @@ def log_request(self, code: t.Union[int, str] = "-", size: t.Union[int, str] = "
 
         code = str(code)
 
-        if click:
-            color = click.style
-
+        if _log_add_style:
             if code[0] == "1":  # 1xx - Informational
-                msg = color(msg, bold=True)
-            elif code[0] == "2":  # 2xx - Success
-                msg = color(msg)
+                msg = _ansi_style(msg, "bold")
+            elif code == "200":  # 2xx - Success
+                pass
             elif code == "304":  # 304 - Resource Not Modified
-                msg = color(msg, fg="cyan")
+                msg = _ansi_style(msg, "cyan")
             elif code[0] == "3":  # 3xx - Redirection
-                msg = color(msg, fg="green")
+                msg = _ansi_style(msg, "green")
             elif code == "404":  # 404 - Resource Not Found
-                msg = color(msg, fg="yellow")
+                msg = _ansi_style(msg, "yellow")
             elif code[0] == "4":  # 4xx - Client Error
-                msg = color(msg, fg="red", bold=True)
+                msg = _ansi_style(msg, "bold", "red")
             else:  # 5xx, or any other response
-                msg = color(msg, fg="magenta", bold=True)
+                msg = _ansi_style(msg, "bold", "magenta")
 
         self.log("info", '"%s" %s %s', msg, code, size)
 
@@ -426,6 +427,22 @@ def log(self, type: str, message: str, *args) -> None:
         )
 
 
+def _ansi_style(value, *styles):
+    codes = {
+        "bold": 1,
+        "red": 31,
+        "green": 32,
+        "yellow": 33,
+        "magenta": 35,
+        "cyan": 36,
+    }
+
+    for style in styles:
+        value = f"\x1b[{codes[style]}m{value}"
+
+    return f"{value}\x1b[0m"
+
+
 def generate_adhoc_ssl_pair(
     cn: t.Optional[str] = None,
 ) -> t.Tuple["Certificate", "RSAPrivateKeyWithSerialization"]: