feat(log): add leveled severity and structured context to log wrappers

log.py was bare print-to-stderr wrappers with no levels or attributable
context (issue #252). Add:

- Ordered severities (debug/info/warn/error) gated by
  BOT_BOTTLE_LOG_LEVEL (default info). debug is silent by default;
  error always surfaces (nothing sits above it), so the fatal die path
  stays visible regardless of configured level.
- An optional `context` mapping on every wrapper, rendered as a
  parseable ` [k=v ...]` suffix (keys sorted; whitespace/quoted values
  quoted) so failures can be filtered and correlated.

Default output with no context is byte-identical to the original lines,
so the 100+ existing single-string call sites are unaffected. Wires the
supervise crash path (the example the issue names) to attach error_type
and crash_log context. Adds test_log.py (backward-compat, context
rendering, level gating, die surfacing).

Closes #252.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YcU7nerbg8cVj9R4EkpfLJ

bot_bottle/cli/supervise.py

@@ -292,7 +292,10 @@ def cmd_supervise(argv: list[str]) -> int:
         return e.code if isinstance(e.code, int) else 1
     except Exception as e:  # noqa: W0718 — catch supervise crash for logging
         log_path = _write_crash_log(e)
-        error(f"supervise crashed: {type(e).__name__}: {e}")
+        error(
+            f"supervise crashed: {type(e).__name__}: {e}",
+            context={"error_type": type(e).__name__, "crash_log": str(log_path)},
+        )
         error(f"full traceback written to {log_path}")
         return 1
     return 0

bot_bottle/log.py

@@ -1,21 +1,107 @@
-"""Tiny logging wrappers. All output goes to stderr."""
+"""Tiny logging wrappers. All output goes to stderr.
+
+Two capabilities layer onto the bare wrappers (issue #252):
+
+  - **Levels.** `debug` / `info` / `warn` / `error` carry an ordered
+    severity. Output is gated by `BOT_BOTTLE_LOG_LEVEL` (debug | info |
+    warn | error; default `info`). A message emits when its severity is
+    at or above the threshold, so `debug` is silent by default and
+    `error` always surfaces (nothing sits above it) — which keeps the
+    fatal `die` path visible regardless of the configured level.
+
+  - **Context.** Every wrapper takes an optional `context` mapping that
+    renders as a parseable ` [k=v ...]` suffix (keys sorted; values with
+    whitespace/quotes are quoted), so failures can be filtered and
+    correlated instead of being flat strings.
+
+With no `context` and the default level, output is byte-identical to the
+original `bot-bottle: <msg>` / `bot-bottle: warning: <msg>` /
+`bot-bottle: error: <msg>` lines — the 100+ existing call sites are
+unaffected.
+"""
 
 from __future__ import annotations
 
+import os
 import sys
-from typing import NoReturn
+from typing import Mapping, NoReturn
+
+# Ordered severities. Gaps left between values so intermediate levels
+# can be added later without renumbering.
+DEBUG = 10
+INFO = 20
+WARN = 30
+ERROR = 40
+
+_LEVEL_NAMES: dict[str, int] = {
+    "debug": DEBUG,
+    "info": INFO,
+    "warn": WARN,
+    "warning": WARN,
+    "error": ERROR,
+}
+
+# Default threshold when BOT_BOTTLE_LOG_LEVEL is unset or unrecognised.
+_DEFAULT_THRESHOLD = INFO
+
+_LOG_LEVEL_ENV = "BOT_BOTTLE_LOG_LEVEL"
 
 
-def info(msg: str) -> None:
-    print(f"bot-bottle: {msg}", file=sys.stderr)
+def _threshold() -> int:
+    """Resolve the active level threshold from the environment.
+
+    Read per-call (not cached) so the level can be changed at runtime
+    and so tests can patch `os.environ` without a reload. Unknown values
+    fall back to the default rather than raising — logging must never be
+    the thing that crashes the process."""
+    raw = os.environ.get(_LOG_LEVEL_ENV, "")
+    return _LEVEL_NAMES.get(raw.strip().lower(), _DEFAULT_THRESHOLD)
 
 
-def warn(msg: str) -> None:
-    print(f"bot-bottle: warning: {msg}", file=sys.stderr)
+def _format_context(context: Mapping[str, object] | None) -> str:
+    """Render a context mapping as a ` [k=v k2=v2]` suffix.
+
+    Keys are sorted for stable, diffable output. Values that are empty or
+    contain whitespace or a quote are wrapped in double quotes (with inner
+    quotes escaped) so each `k=v` pair stays parseable. Empty/None context
+    renders as the empty string."""
+    if not context:
+        return ""
+    parts: list[str] = []
+    for key in sorted(context):
+        value = str(context[key])
+        if value == "" or any(ch.isspace() for ch in value) or '"' in value:
+            value = '"' + value.replace('"', '\\"') + '"'
+        parts.append(f"{key}={value}")
+    return " [" + " ".join(parts) + "]"
 
 
-def error(msg: str) -> None:
-    print(f"bot-bottle: error: {msg}", file=sys.stderr)
+def _emit(
+    level: int,
+    label: str,
+    msg: str,
+    context: Mapping[str, object] | None,
+) -> None:
+    if level < _threshold():
+        return
+    prefix = f"{label}: " if label else ""
+    sys.stderr.write(f"bot-bottle: {prefix}{msg}{_format_context(context)}\n")
+
+
+def debug(msg: str, *, context: Mapping[str, object] | None = None) -> None:
+    _emit(DEBUG, "debug", msg, context)
+
+
+def info(msg: str, *, context: Mapping[str, object] | None = None) -> None:
+    _emit(INFO, "", msg, context)
+
+
+def warn(msg: str, *, context: Mapping[str, object] | None = None) -> None:
+    _emit(WARN, "warning", msg, context)
+
+
+def error(msg: str, *, context: Mapping[str, object] | None = None) -> None:
+    _emit(ERROR, "error", msg, context)
 
 
 class Die(SystemExit):
@@ -31,6 +117,6 @@ class Die(SystemExit):
         self.message = message
 
 
-def die(msg: str) -> NoReturn:
-    error(msg)
+def die(msg: str, *, context: Mapping[str, object] | None = None) -> NoReturn:
+    error(msg, context=context)
     raise Die(1, msg)