fix: prune/retier recognize legacy rolls named off the live name; correct gzip docs

Legacy pre-v0.5.0 daily rolls were named off the LIVE file name (run.log.<date>), but
prune/retier only matched the history stem (the cwd basename), so in the default upgrade
path an existing legacy backlog was never recognized and piled up forever. prune/retier/
make_rotator/attach_rolling now thread the live name as an optional live_stem so both shapes
are pruned; a foreign same-stem file is still left alone (all forms stay date-bearing).
README + CLAUDE.md corrected to describe the atomic compress-or-skip behavior (40310b8 removed
the runtime _gz_intact reconciliation the docs still claimed).

Signed-off-by: disqualifier <dev@disqualifier.me>

README.md

@@ -258,13 +258,13 @@ setup_logging(name="run", queue=True)
   rotate-mode aware: the zero-retention delete only ever fires for `"size"`, matching the
   contract in the bullet above — `"daily"`/`"on_start"` with `backup_count=0` were always
   meant to roll without pruning and now do again.
-- **Gzip writes are crash-safe (v0.5.1+).** `_gzip_file` now writes to a `.tmp` sibling and
-  atomically `os.replace`s it onto the final `.gz` path, so a crash/OOM/power-loss mid-write
-  can never leave a truncated `.gz` at the path retention logic trusts. Tiered retention's
-  plain/gz dedupe additionally verifies a `.gz` decompresses cleanly before deleting its
-  plain twin — a corrupt `.gz` (from before this fix, or an external cause) is never
-  preferred over an intact plain copy; the plain is kept and the `.gz` gets rewritten
-  cleanly on the next retier pass instead of being deleted.
+- **Gzip is atomic compress-or-skip (v0.5.1+).** `_gzip_file` writes to a `.tmp` sibling,
+  verifies it decompresses cleanly, and only then `os.replace`s it onto the final `.gz` and
+  removes the plain source — a crash/OOM/interrupt at any point leaves the plain `.log`
+  intact with no `.gz` (or the `.tmp` cleaned up), so this code never produces a truncated
+  `.gz` at the path retention trusts. Because a corrupt `.gz` can't arise from this path, the
+  tiered retention dedupe drops a plain twin unconditionally when its `.gz` exists (no
+  runtime `_gz_intact` reconciliation — that was removed once compression became atomic).
 - **Setup-time warnings reach the log file (v0.6.0+).** Previously, a warning raised
   during `setup_logging` itself (an invalid `module_levels` entry, a handler failing to
   close on re-setup, an unknown `rotate` value) was emitted *before* any handler was

src/log_setup/rotation.py

@@ -132,7 +132,7 @@ def make_rotator(
     compress: bool, log_dir: Optional[str] = None,
     prune_stem: Optional[str] = None, backup_count: int = 0,
     keep_uncompressed: Optional[int] = None, keep_compressed: Optional[int] = None,
-    rotate_mode: Optional[str] = None,
+    rotate_mode: Optional[str] = None, live_stem: Optional[str] = None,
 ) -> Callable[[str, str], None]:
     """rotator: move (or gzip) the source live file to the destination rolled path
 
@@ -162,7 +162,7 @@ def make_rotator(
             plain_dest = _free_dest(dest[:-3] if dest.endswith(".gz") else dest)
             _move(source, plain_dest)
             if log_dir is not None and prune_stem is not None:
-                retier(log_dir, prune_stem, keep_uncompressed or 0, keep_compressed or 0)
+                retier(log_dir, prune_stem, keep_uncompressed or 0, keep_compressed or 0, live_stem)
             return
         if compress:
             _gzip_file(source, dest)
@@ -175,7 +175,7 @@ def make_rotator(
                 except OSError:
                     pass
         elif log_dir is not None and prune_stem is not None:
-            prune(log_dir, prune_stem, backup_count)
+            prune(log_dir, prune_stem, backup_count, live_stem)
     return rotator
 
 
@@ -225,7 +225,8 @@ def rotate_on_start(
         retier(log_dir, stem, keep_uncompressed or 0, keep_compressed or 0)
 
 
-def retier(log_dir: str, stem: str, keep_uncompressed: int, keep_compressed: int) -> None:
+def retier(log_dir: str, stem: str, keep_uncompressed: int, keep_compressed: int,
+           live_stem: Optional[str] = None) -> None:
     """re-tier rolled files for stem: newest plain, next gzipped, rest deleted
 
     newest-first by mtime: the first `keep_uncompressed` stay uncompressed, the next
@@ -248,10 +249,11 @@ def retier(log_dir: str, stem: str, keep_uncompressed: int, keep_compressed: int
     the same log_dir) is left alone rather than tiered/gzipped/deleted.
     """
     stem = os.path.basename(stem)
+    live_stem = os.path.basename(live_stem) if live_stem else None
     try:
         names = [
             name for name in os.listdir(log_dir)
-            if name != f"{stem}.log" and _is_rolled_name(stem, name)
+            if name != f"{stem}.log" and _is_rolled_name(stem, name, live_stem)
         ]
     except OSError:
         return
@@ -297,26 +299,30 @@ def retier(log_dir: str, stem: str, keep_uncompressed: int, keep_compressed: int
                 pass
 
 
-def _rolled_name_pattern(stem: str) -> "re.Pattern":
+def _rolled_name_pattern(stem: str, live_stem: Optional[str] = None) -> "re.Pattern":
     """compiled regex matching this lib's own rolled-file shapes for stem
 
-    two forms, both date-bearing so a foreign same-stem file (e.g. `proj.audit.log`) is
+    all forms are date-bearing so a foreign same-stem file (e.g. `proj.audit.log`) is
     never mistaken for a roll and pruned/retiered/deleted:
     - current uniform namer: `<stem>.<Y-m-d_H-M-S>[.N].log[.gz]`
       (make_history_namer/rotate_on_start, see attach_rolling)
     - legacy pre-v0.5.0 daily: `<stem>.log.<Y-m-d>[.gz]` (the stdlib TimedRotatingFileHandler
       shape) - matched so an upgraded deployment's existing history is still pruned/retired
-      instead of piling up forever
+      instead of piling up forever. legacy rolls were named off the LIVE file's name, not the
+      history stem, so when `live_stem` is given (and differs) its legacy shape is matched too
     """
-    esc = re.escape(stem)
-    uniform = rf"{esc}\.\d{{4}}-\d{{2}}-\d{{2}}_\d{{2}}-\d{{2}}-\d{{2}}(?:\.\d+)?\.log(?:\.gz)?"
-    legacy = rf"{esc}\.log\.\d{{4}}-\d{{2}}-\d{{2}}(?:\.gz)?"
-    return re.compile(rf"^(?:{uniform}|{legacy})$")
+    stems = [stem] if live_stem is None or live_stem == stem else [stem, live_stem]
+    forms = []
+    for s in stems:
+        esc = re.escape(s)
+        forms.append(rf"{esc}\.\d{{4}}-\d{{2}}-\d{{2}}_\d{{2}}-\d{{2}}-\d{{2}}(?:\.\d+)?\.log(?:\.gz)?")
+        forms.append(rf"{esc}\.log\.\d{{4}}-\d{{2}}-\d{{2}}(?:\.gz)?")
+    return re.compile(rf"^(?:{'|'.join(forms)})$")
 
 
-def _is_rolled_name(stem: str, name: str) -> bool:
-    """return whether name has this lib's own rolled-log shape for stem"""
-    return _rolled_name_pattern(stem).match(name) is not None
+def _is_rolled_name(stem: str, name: str, live_stem: Optional[str] = None) -> bool:
+    """return whether name has this lib's own rolled-log shape for stem (or the live stem)"""
+    return _rolled_name_pattern(stem, live_stem).match(name) is not None
 
 
 def _roll_counter(path: str) -> int:
@@ -335,7 +341,7 @@ def _roll_counter(path: str) -> int:
     return int(tail) if tail.isdigit() else 0
 
 
-def prune(log_dir: str, stem: str, backup_count: int) -> None:
+def prune(log_dir: str, stem: str, backup_count: int, live_stem: Optional[str] = None) -> None:
     """keep only the newest `backup_count` rolled files for a given stem in log_dir
 
     matches files beginning with `<stem>.` (e.g. run.*), sorted newest-first by mtime
@@ -354,11 +360,12 @@ def prune(log_dir: str, stem: str, backup_count: int) -> None:
     if backup_count <= 0:
         return
     stem = os.path.basename(stem)
+    live_stem = os.path.basename(live_stem) if live_stem else None
     try:
         entries = [
             os.path.join(log_dir, name)
             for name in os.listdir(log_dir)
-            if name != f"{stem}.log" and _is_rolled_name(stem, name)
+            if name != f"{stem}.log" and _is_rolled_name(stem, name, live_stem)
         ]
     except OSError:
         return
@@ -403,9 +410,13 @@ def attach_rolling(
     namer = make_history_namer(
         os.path.basename(prune_stem or ""), log_dir, compress, plain=tiered,
     )
+    # the live file name (stem of the handler's baseFilename, minus one .log) - so retention
+    # also recognizes pre-v0.5.0 legacy rolls, which were named off the LIVE name not the stem
+    live_base = os.path.basename(getattr(handler, "baseFilename", "") or "")
+    live_stem = live_base[:-4] if live_base.endswith(".log") else live_base
     rotator = make_rotator(
         compress, log_dir, prune_stem, backup_count, keep_uncompressed, keep_compressed,
-        rotate_mode=rotate_mode,
+        rotate_mode=rotate_mode, live_stem=live_stem or None,
     )
     handler.namer = namer
     handler.rotator = rotator

src/log_setup/setup.py

@@ -185,7 +185,9 @@ def _file_handler(
                 )
             else:
                 rotate_on_start(live_path, log_dir, compress, history_stem=history_stem)
-                prune(log_dir, history_stem, backup_count)
+                live_base = os.path.basename(live_path)
+                live_stem = live_base[:-4] if live_base.endswith(".log") else live_base
+                prune(log_dir, history_stem, backup_count, live_stem or None)
         elif rotate is not None:
             # a typo'd value would otherwise silently fall through to a non-rotating
             # FileHandler and grow forever - warn instead of degrade silently