Detect color support on stderr, matching where logs are written

Store the two-digit WS id (colored when stderr supports color, plain
otherwise) in the ASGI scope state so user code can include it in its
own log lines via websocket.state.logid.

Move terminal helpers (use_color, strip_ansi, display width) into a new
dependency-free fastapi_vue.tty module, absorbing termwidth.py, to keep
imports one-directional and avoid the logging/accesslog cycle.

fastapi-vue/fastapi_vue/accesslog.py

@@ -9,7 +9,7 @@ import time
 from ipaddress import IPv6Address
 from typing import TYPE_CHECKING, cast
 
-from .termwidth import pad_display
+from .tty import pad_display, use_color
 
 if TYPE_CHECKING:
     from uvicorn._types import (
@@ -388,6 +388,7 @@ class AccessLogMiddleware:
             if message["type"] == "websocket.accept" and not accepted:
                 accepted = True
                 ws_id = _next_ws_id()
+                www_scope["state"]["logid"] = f"{_WS_OPEN}{ws_id}{_RESET}" if use_color() else ws_id
                 fields = _ws_open_extra(www_scope, ws_id, origin, _extra())
                 logger.info(_assemble_access_log(fields), extra=fields)
             elif message["type"] == "websocket.http.response.start" and not closed:

fastapi-vue/fastapi_vue/logging.py

@@ -10,9 +10,6 @@ from __future__ import annotations
 
 import io
 import logging
-import os
-import re
-import sys
 from contextlib import suppress
 from copy import deepcopy
 from typing import TYPE_CHECKING, Literal
@@ -32,8 +29,7 @@ if TYPE_CHECKING:
 
 from .accesslog import AccessLogMiddleware
 from .environ import env
-
-ANSI_ESCAPE_RE = re.compile(r"\x1b\[[0-9;]*m")
+from .tty import strip_ansi, use_color
 
 RESET = "\033[0m"
 
@@ -42,26 +38,6 @@ ACCESS_LOG_FMT = "%(client)s %(status)s %(method)s %(host)s%(path)s %(extra)s%(t
 ACCESS_LOGGER = "fastapi_vue.access"
 
 
-def strip_ansi(text: str) -> str:
-    """Remove ANSI escape codes from text."""
-    return ANSI_ESCAPE_RE.sub("", text)
-
-
-def use_color(stream: io.TextIOBase = sys.stderr) -> bool:
-    """Test if the stream supports color codes."""
-    if os.environ.get("NO_COLOR"):  # Non empty means no (no-color.org)
-        return False
-    if os.environ.get("FORCE_COLOR", "") not in {"", "0"}:  # force-color.org, node
-        return True
-    if hasattr(stream, "isatty") and stream.isatty():
-        return True
-    with suppress(KeyError, ValueError, OSError):  # Journald does color (-ocat)
-        dev, ino = map(int, os.environ["JOURNAL_STREAM"].split(":", 1))
-        st = os.fstat(stream.fileno())
-        return st.st_dev == dev and st.st_ino == ino
-    return False
-
-
 _LEVEL_EMOJI = {
     logging.DEBUG: "🐛",
     logging.INFO: "🔷",
@@ -115,7 +91,7 @@ class Formatter(logging.Formatter):
         if use_colors in (True, False):
             self.use_colors = use_colors
         else:
-            self.use_colors = use_color(sys.stdout)
+            self.use_colors = use_color()
         super().__init__(fmt=fmt, datefmt=datefmt, style=style)
 
     def formatMessage(self, record: logging.LogRecord) -> str:  # noqa: N802

fastapi-vue/fastapi_vue/server.py

@@ -22,9 +22,9 @@ from .logging import (
     patch_lifespan_logging,
     patch_log_config,
     patch_server_error_middleware,
-    use_color,
 )
 from .startupbox import print_box
+from .tty import use_color
 
 tracerite.load()  # Early load on CLI load (import server); uvicorn workers reload via log config
 

fastapi-vue/fastapi_vue/startupbox.py

@@ -2,14 +2,14 @@
 
 import sys
 
-from .termwidth import display_width, pad_display
+from .tty import display_width, pad_display
 
 
 def print_box(text: str) -> None:
     """Print text in a rounded unicode box sized to its longest line.
 
     The text is split on newlines as-is (not trimmed). Padding accounts
-    for ANSI colors and unicode display width (see termwidth.display_width).
+    for ANSI colors and unicode display width (see tty.display_width).
     """
     lines = text.split("\n")
     width = max(map(display_width, lines))

fastapi-vue/fastapi_vue/tty.py

@@ -1,11 +1,37 @@
-"""Terminal display width calculation for unicode and ANSI-colored text."""
+"""Terminal color detection, ANSI helpers, and display width calculation."""
 
+from __future__ import annotations
+
+import io
+import os
 import re
+import sys
 import unicodedata
+from contextlib import suppress
 
 ANSI_ESCAPE_RE = re.compile(r"\x1b\[[0-9;:]*[A-Za-z]")
 
 
+def strip_ansi(text: str) -> str:
+    """Remove ANSI escape codes from text."""
+    return ANSI_ESCAPE_RE.sub("", text)
+
+
+def use_color(stream: io.TextIOBase = sys.stderr) -> bool:
+    """Test if the stream supports color codes."""
+    if os.environ.get("NO_COLOR"):  # Non empty means no (no-color.org)
+        return False
+    if os.environ.get("FORCE_COLOR", "") not in {"", "0"}:  # force-color.org, node
+        return True
+    if hasattr(stream, "isatty") and stream.isatty():
+        return True
+    with suppress(KeyError, ValueError, OSError):  # Journald does color (-ocat)
+        dev, ino = map(int, os.environ["JOURNAL_STREAM"].split(":", 1))
+        st = os.fstat(stream.fileno())
+        return st.st_dev == dev and st.st_ino == ino
+    return False
+
+
 def _is_wide(char: str) -> bool:
     """Return True for characters rendered as two terminal columns."""
     if unicodedata.east_asian_width(char) in {"F", "W"}: