Merge pull request #533 from got-feedback/feat/feedpak-jsonc

feat(core): read .jsonc data files (strip C-style comments) (feedpak-spec §8)

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
+- **`.jsonc` support for feedpak data files** (feedpak-spec §8, FEP #3 / PR #13). Hand-edited packs may now use the `.jsonc` extension (JSON with C-style `//` line and `/* */` block comments) for any data file the manifest points at — arrangements, notation sidecars, `drum_tab`, `song_timeline`, `lyrics`, and `keys`. New shared `lib/jsonc.py` provides `parse_jsonc(text)` + `load_json(path)` (auto-detects `.jsonc` by suffix, string-aware so comment-like text inside JSON string values is preserved) and is now used by every reader in `lib/sloppak.py` (six side-file sites) and `scripts/lift_keys_notation.py` (three arrangement / song_timeline read sites). The strip regex mirrors the reference validator in `feedpak-spec/tools/validate.py`. This is an additive (MINOR) change: `.jsonc` is opt-in, so any pack that keeps its data files as `.json` is unaffected and needs no regeneration. Note that a `.jsonc` file containing real comments only loads on a reader that implements §8 — a pre-this-change reader calls bare `json.loads` and fails on the comments rather than ignoring them, so don't hand out `.jsonc` packs to older hosts. Tests: `tests/test_sloppak_jsonc_load.py` (covers all six side-file types, the lift helper, and the string-boundary preservation rule end-to-end).
 - **The highway now loads the part that matches your selected instrument — a bass player gets the Bass arrangement, not the default Lead/guitar chart.** When you open a song without an explicit arrangement, the WebSocket handler (`server.py` `highway_ws`) reads your selected `instrument` from `config.json` (the same file it already reads for your default-arrangement preference) and routes to the matching part: **bass → the Bass arrangement**; guitar — and any unknown/future instrument (drums, keys) — falls through to the existing preference/most-notes default, which already lands on a guitar part. Previously the instrument selector only fed the tuner, so a bass player was handed a guitar chart (and a tune/coverage check then compared a 4-string bass against a 6-string part). An **explicit arrangement request always wins** (a manual arrangement switch is untouched), and a bass player's saved default-arrangement preference is still honored **within** the bass parts (so a preferred `Bass 2` / `Alt. Bass` wins over the canonical Bass), so this only changes the *default* part chosen on load. Server-only — every launch path already flows through the WS, so there's no client change. This is the instrument↔chart-routing piece the working-tuning series leans on (otherwise coverage compares across instruments). Tests: `tests/test_highway_ws_instrument_routing.py` (bass→Bass, bass-honors-pref, bass-no-bass-part→guitar, guitar→default, explicit-wins).
 - **Host "working tuning" — a live, app-wide record of what tuning your instrument is *actually* in right now (foundation; no behavior change yet).** Introduces `window.feedBack.workingTuning`, a host-owned, session-lived state distinct from any one song's tuning and from a soft opt-in default: the offsets + string-count + reference pitch the player's instrument is currently in, plus an `assumed`/`verified` provenance flag. It's **per-instrument** — your guitar's current tuning and your bass's are kept *separately* (keyed like the instrument selector, e.g. `guitar-6` / `bass-4`), so switching instruments surfaces that instrument's own remembered tuning and you only ever deal with the one you've selected. It exists so a retune — or an instrument swap mid-session — is reflected **everywhere** (the highway, the library/song-picker, and plugins like the tuner, Virtuoso, and the minigames) instead of being re-derived per surface or wrongly assumed from a fixed profile. Modeled on the shipped `tuning` capability + the `feedBack.theme` read-API: a **synchronous `get(instrument?)`** (returns the selected instrument's state, defaulting to the seed until known), a `set(state, {provenance, instrument})` mutator (the tuner becomes the sole writer in the next change), `setCurrentInstrument()` for the selector, `resetToDefault()`, and a `working-tuning-changed` event that fires on every change **and once on hydration** (carrying which instrument changed) so a late-mounting consumer is never stuck on stale state. State is **in-memory, seeded from `/api/settings` on boot and reset on restart** — a stale "you're in drop-A" assumption is worse than re-asking. Registered as a separate `working-tuning` **exclusive-owner** capability (tuner = writer, the rest = requesters). This is the foundation (plumbing only — nothing writes to it yet) of the working-tuning series, which fixes the tuner gate only ever prompting *away from* a fixed "home" tuning (never back) and makes the current tuning a first-class signal the whole app shares. Offsets use the same per-string semitone vocabulary as song tunings, so fully custom/extended tunings (e.g. a drop-A 8-string) are first-class. Frontend-only: new `static/capabilities/working-tuning.js`, loaded from `static/index.html` + `static/v3/index.html`.
 - **The v3 Songs grid is now DOM-virtualized — card-node count stays bounded no matter how big the library is or how far you scroll.** The grid used to append every scrolled page and never let go, so a 2000-song library grew the DOM from 24 → 624 → 2001 card nodes as you scrolled (layout/memory cost scaling with depth). It now renders only the **visible window** of cards (± a small overscan); a sizer element sized to the whole library (`ceil(total/cols) × rowH`) gives the scrollbar its full geometry while the grid is absolutely positioned to the first visible row. `state.songs` is a sparse, absolutely-indexed store fetched a page at a time on demand — using the stage-1 **keyset cursor** for contiguous forward scroll (O(page)) and falling back to `OFFSET page=` for jumps/restore/non-keyset providers (collections, remote). Verified bounded (~60 nodes for a 2001-song library while the count still reads "2001 songs"). The **A–Z rail now seeks directly**: `sort_letters` gives a letter's first-row index (cumulative of prior buckets), converted to a scrollTop in O(1) — no more paging through every intervening row (a bounded forward scan covers the rare legacy provider without `sort_letters`). Select-mode selections, accuracy badges, the ⋮ card menu, plugin card actions, scroll-restore (now scrollTop-based, since geometry is stable), and the tree/folder views all survive cards leaving and re-entering the DOM. Plugins that decorate cards get a stable `window.v3Songs.visibleCards()` accessor + a `v3:library-window-rendered` event instead of assuming every card is present (the highway-stutter lesson). Stage 2 of the virtualized-grid project (got-feedback/feedBack#636 item 3), building on the stage-1 keyset data layer below. Frontend-only: `static/v3/songs.js`, `static/v3/v3.css`. Tests: `tests/browser/v3-grid-virtualization.spec.ts` (bounded-DOM invariant across a 2001-song scroll + direct rail jump), updated `tests/js/v3_az_rail.test.js` + `tests/js/v3_songs_scroll.test.js`.

lib/jsonc.py

@@ -0,0 +1,56 @@
+"""JSONC support — JSON with C-style comments.
+
+Per feedpak-spec §8: when a manifest pointer resolves to a ``.jsonc`` file, a
+Reader MUST strip ``//`` line comments and ``/* */`` block comments before
+parsing the JSON content. This module implements that stripping in a single
+shared place so every sloppak/feedpak reader in this repo parses ``.jsonc``
+the same way (string-aware so comment-like text inside JSON strings survives).
+
+The regex mirrors the reference implementation in ``feedpak-spec/tools/validate.py``.
+``load_json(path)`` auto-detects ``.jsonc`` by suffix; plain ``.json`` (and any
+other extension) goes straight through ``json.loads``. Use it as a drop-in
+replacement for ``json.loads(path.read_text(encoding="utf-8"))``.
+"""
+
+from __future__ import annotations
+
+import json
+import re
+from pathlib import Path
+
+# Match JSON string literals (preserved), // line comments, and /* block */
+# comments. A single combined alternation processed by `sub` with a callback
+# that keeps strings and replaces comments with the empty string — so
+# comment-like text inside a string literal is never stripped.
+_JSONC_STRIP_RE = re.compile(
+    r'"(?:[^"\\]|\\.)*"|'   # string literal — keep as-is
+    r'//.*|'                 # // line comment — strip
+    r'/\*[\s\S]*?\*/',       # /* block comment */ — strip
+)
+
+
+def parse_jsonc(text: str) -> object:
+    """Parse a JSONC string, stripping C-style comments before JSON parsing.
+
+    Handles ``//`` line comments and ``/* */`` block comments, respecting
+    string boundaries so that comment-like text inside strings is preserved.
+    Raises ``json.JSONDecodeError`` on malformed JSON (after stripping).
+    """
+    stripped = _JSONC_STRIP_RE.sub(
+        lambda m: m.group(0) if m.group(0).startswith('"') else '',
+        text,
+    )
+    return json.loads(stripped)
+
+
+def load_json(path: Path) -> object:
+    """Read and parse a JSON/JSONC file by path.
+
+    Files ending in ``.jsonc`` are stripped of comments via :func:`parse_jsonc`;
+    all other files are parsed as plain JSON. UTF-8 encoded, matching every
+    other reader in this repo.
+    """
+    raw = path.read_text(encoding="utf-8")
+    if path.name.lower().endswith(".jsonc"):
+        return parse_jsonc(raw)
+    return json.loads(raw)

lib/sloppak.py

@@ -13,7 +13,6 @@ See the format spec in the project's sloppak plan for the full layout.
 
 from __future__ import annotations
 
-import json
 import logging
 import math
 import shutil
@@ -37,6 +36,7 @@ SONG_EXTS = (FEEDPAK_EXT, SLOPPAK_EXT)  # accepted on read/discovery
 
 import yaml
 
+from jsonc import load_json
 from safepath import safe_join
 from song import (
     Song,
@@ -423,7 +423,7 @@ def load_song(
             if not arr_path.exists():
                 continue
             try:
-                data = json.loads(arr_path.read_text(encoding="utf-8"))
+                data = load_json(arr_path)
             except Exception as e:
                 log.debug("sloppak: failed to parse arrangement %r: %s", rel, e)
                 continue
@@ -489,7 +489,7 @@ def load_song(
         raw_nt = None
         if nt_path is not None and nt_path.exists():
             try:
-                raw_nt = json.loads(nt_path.read_text(encoding="utf-8"))
+                raw_nt = load_json(nt_path)
             except Exception as e:
                 log.warning("sloppak: failed to parse notation %r: %s", notation_rel, e)
         if raw_nt is not None:
@@ -528,7 +528,7 @@ def load_song(
             dt_path = None
         if dt_path is not None and dt_path.exists():
             try:
-                raw = json.loads(dt_path.read_text(encoding="utf-8"))
+                raw = load_json(dt_path)
             except Exception as e:
                 log.warning("sloppak: failed to parse drum_tab %r: %s", drum_tab_rel, e)
                 raw = None
@@ -588,7 +588,7 @@ def load_song(
             st_path = None
         if st_path is not None and st_path.exists():
             try:
-                raw = json.loads(st_path.read_text(encoding="utf-8"))
+                raw = load_json(st_path)
             except Exception as e:
                 log.warning("sloppak: failed to parse song_timeline %r: %s", song_timeline_rel, e)
                 raw = None
@@ -686,7 +686,7 @@ def load_song(
             lyr_path = None
         if lyr_path is not None and lyr_path.exists():
             try:
-                raw = json.loads(lyr_path.read_text(encoding="utf-8"))
+                raw = load_json(lyr_path)
             except Exception as e:
                 log.debug("sloppak: failed to parse lyrics %r: %s", lyrics_rel, e)
                 raw = None
@@ -773,7 +773,7 @@ def load_song(
             k_path = None
         if k_path is not None and k_path.exists():
             try:
-                raw = json.loads(k_path.read_text(encoding="utf-8"))
+                raw = load_json(k_path)
             except Exception as e:
                 log.warning("sloppak: failed to parse keys %r: %s", keys_rel, e)
                 raw = None

scripts/lift_keys_notation.py

@@ -60,6 +60,8 @@ import yaml  # noqa: E402
 
 import notation as notation_mod  # noqa: E402, F401  (re-exported for tests)
 
+from jsonc import load_json  # noqa: E402
+
 # The wire→notation heuristic core lives in ``lib/notation_lift.py`` so it can
 # be reused in-process (e.g. by the Arrangement Editor's notation save path)
 # rather than being copy-pasted out of this one-time CLI. Re-exported here so
@@ -106,15 +108,16 @@ def _parse_time_signature(raw: object) -> tuple[int, int]:
 
 
 def _load_song_beats(pak: Path, manifest: dict) -> list[dict]:
-    """Song-level beats: ``song_timeline.json`` when present, else the first
+    """Song-level beats: the ``song_timeline`` file when present, else the first
     arrangement JSON that carries a non-empty ``beats`` array (the loader's
-    legacy convention)."""
+    legacy convention). Both the timeline and arrangement files are read via
+    ``load_json``, so either may be ``.json`` or ``.jsonc``."""
     st_rel = manifest.get("song_timeline")
     if isinstance(st_rel, str) and st_rel:
         st_path = _safe_child(pak, st_rel)
         if st_path is not None and st_path.is_file():
             try:
-                data = json.loads(st_path.read_text(encoding="utf-8"))
+                data = load_json(st_path)
                 # An empty beats list is not an authoritative timeline — fall
                 # through to the arrangement JSONs rather than ending up with
                 # zero downbeats and skipping the whole sloppak.
@@ -134,7 +137,7 @@ def _load_song_beats(pak: Path, manifest: dict) -> list[dict]:
         if arr_path is None or not arr_path.is_file():
             continue
         try:
-            data = json.loads(arr_path.read_text(encoding="utf-8"))
+            data = load_json(arr_path)
         except (OSError, ValueError):
             continue
         if isinstance(data, dict):
@@ -219,7 +222,7 @@ def lift_sloppak(pak: Path, *, dry_run: bool = False) -> list[str]:
             continue
 
         try:
-            arr_data = json.loads(arr_path.read_text(encoding="utf-8"))
+            arr_data = load_json(arr_path)
         except (OSError, ValueError) as e:
             log.warning("%s/%s: unreadable arrangement JSON (%s) — skipped",
                         pak.name, arr_id, e)

tests/test_sloppak_jsonc_load.py

@@ -0,0 +1,335 @@
+"""Tests for .jsonc support in the sloppak/feedpak loaders (feedpak-spec §8).
+
+When a manifest pointer resolves to a ``.jsonc`` file, the reader MUST strip
+C-style comments (``//`` line and ``/* */`` block) before parsing. These tests
+exercise every side-file reader in ``lib/sloppak.py`` (arrangement, notation,
+drum_tab, song_timeline, lyrics, keys) plus the arrangement/song_timeline
+reads in ``scripts/lift_keys_notation.py`` against ``.jsonc`` inputs, and pin
+the string-boundary rule (comment-like text inside a JSON string survives).
+"""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+import pytest
+import yaml
+
+import sloppak as sloppak_mod
+from jsonc import parse_jsonc
+from scripts.lift_keys_notation import _load_song_beats
+
+
+# ── jsonc.parse_jsonc unit tests ─────────────────────────────────────────────
+
+def test_parse_jsonc_strips_line_comment():
+    assert parse_jsonc('{"a": 1 // c\n}') == {"a": 1}
+
+
+def test_parse_jsonc_strips_block_comment():
+    assert parse_jsonc('{"a": /* x */ 2}') == {"a": 2}
+
+
+def test_parse_jsonc_strips_multiline_block_comment():
+    text = '{\n  /* multi\n     line */\n  "a": 1\n}'
+    assert parse_jsonc(text) == {"a": 1}
+
+
+def test_parse_jsonc_preserves_comment_like_text_in_strings():
+    # ``//`` and ``/*`` inside a JSON string literal must NOT be treated as
+    # comments — the string-aware regex keeps them verbatim.
+    text = '{"url": "https://x/y", "note": "// not a comment /* still not */"}'
+    out = parse_jsonc(text)
+    assert out["url"] == "https://x/y"
+    assert out["note"] == "// not a comment /* still not */"
+
+
+def test_parse_jsonc_rejects_malformed():
+    with pytest.raises(json.JSONDecodeError):
+        parse_jsonc('{"a": // comment breaks value\n}')
+
+
+def test_parse_jsonc_plain_json_passes_through():
+    assert parse_jsonc('{"a": 1}') == {"a": 1}
+
+
+# ── Fixture builder ──────────────────────────────────────────────────────────
+
+def _base_arrangement(*, beats=None) -> dict:
+    return {
+        "name": "Lead", "tuning": [0, 0, 0, 0, 0, 0], "capo": 0,
+        "notes": [], "chords": [], "anchors": [], "handshapes": [],
+        "templates": [], "beats": beats or [], "sections": [],
+    }
+
+
+def _write_sloppak(root: Path, *, manifest_extras: dict, side_files: dict) -> Path:
+    """Build a minimal directory-form sloppak.
+
+    ``side_files`` maps a pak-relative filename (e.g. ``"arrangements/lead.jsonc"``)
+    to the exact text to write — so the caller controls comments / extensions.
+    """
+    pak = root / f"{root.name}.sloppak"
+    pak.mkdir()
+    (pak / "arrangements").mkdir()
+    # A default lead arrangement file the manifest references; can be overridden
+    # via side_files if the caller wants a .jsonc arrangement.
+    if "arrangements/lead.json" not in side_files and "arrangements/lead.jsonc" not in side_files:
+        (pak / "arrangements" / "lead.json").write_text(
+            json.dumps(_base_arrangement())
+        )
+    for rel, text in side_files.items():
+        target = pak / rel
+        target.parent.mkdir(parents=True, exist_ok=True)
+        target.write_text(text, encoding="utf-8")
+    manifest = {
+        "title": "Test", "artist": "Tester", "album": "", "year": 2026,
+        "duration": 10.0,
+        "arrangements": [{"id": "lead", "name": "Lead", "file": "arrangements/lead.json"}],
+        "stems": [{"id": "full", "file": "stems/full.ogg", "default": True}],
+    }
+    manifest.update(manifest_extras)
+    (pak / "manifest.yaml").write_text(yaml.safe_dump(manifest, sort_keys=False))
+    return pak
+
+
+def _load(pak_path: Path, tmp_path: Path):
+    dlc_root = pak_path.parent
+    cache = tmp_path / "cache"
+    cache.mkdir()
+    return sloppak_mod.load_song(pak_path.name, dlc_root, cache)
+
+
+# ── Arrangement .jsonc ───────────────────────────────────────────────────────
+
+def test_load_arrangement_jsonc_with_comments(tmp_path: Path):
+    arr_text = (
+        '// lead chart\n'
+        '{\n'
+        '  "name": "Lead",\n'
+        '  "tuning": [0, 0, 0, 0, 0, 0],\n'
+        '  "capo": 0,\n'
+        '  /* no notes yet */\n'
+        '  "notes": [{"t": 0.5, "s": 0, "f": 5, "sus": 0}],\n'
+        '  "chords": [], "anchors": [], "handshapes": [], "templates": [],\n'
+        '  "beats": [], "sections": []\n'
+        '}'
+    )
+    pak = _write_sloppak(
+        tmp_path,
+        manifest_extras={
+            "arrangements": [{"id": "lead", "name": "Lead",
+                              "file": "arrangements/lead.jsonc"}]
+        },
+        side_files={"arrangements/lead.jsonc": arr_text},
+    )
+    loaded = _load(pak, tmp_path)
+    assert len(loaded.song.arrangements) == 1
+    arr = loaded.song.arrangements[0]
+    assert arr.name == "Lead"
+    assert len(arr.notes) == 1
+    assert arr.notes[0].fret == 5
+
+
+def test_load_arrangement_jsonc_malformed_is_skipped(tmp_path: Path):
+    # A .jsonc file that is still invalid after stripping comments must be
+    # skipped gracefully (the loader's existing permissive path), not crash.
+    pak = _write_sloppak(
+        tmp_path,
+        manifest_extras={
+            "arrangements": [{"id": "lead", "name": "Lead",
+                              "file": "arrangements/lead.jsonc"}]
+        },
+        side_files={"arrangements/lead.jsonc": '{"notes": // broken\n}'},
+    )
+    loaded = _load(pak, tmp_path)
+    # The malformed arrangement is skipped; load still returns a song shell.
+    assert len(loaded.song.arrangements) == 0
+
+
+# ── Notation .jsonc ──────────────────────────────────────────────────────────
+
+def test_load_notation_jsonc_with_comments(tmp_path: Path):
+    from tests.test_sloppak_notation_load import VALID_NOTATION
+    payload = VALID_NOTATION
+    text = (
+        '/* notation for keys */\n'
+        + json.dumps(payload)
+    )
+    pak = _write_sloppak(
+        tmp_path,
+        manifest_extras={
+            "arrangements": [{"id": "lead", "name": "Lead",
+                              "file": "arrangements/lead.json",
+                              "notation": "notation_lead.jsonc"}]
+        },
+        side_files={"notation_lead.jsonc": text},
+    )
+    loaded = _load(pak, tmp_path)
+    assert loaded.notation_by_id is not None
+    assert "lead" in loaded.notation_by_id
+
+
+# ── drum_tab .jsonc ──────────────────────────────────────────────────────────
+
+def test_load_drum_tab_jsonc_with_comments(tmp_path: Path):
+    payload = {
+        "version": 1, "name": "Drums",
+        "kit": [{"id": "kick", "name": "Kick"}],
+        "hits": [{"t": 0.5, "p": "kick", "v": 110}],
+    }
+    text = '// drum tab\n' + json.dumps(payload)
+    pak = _write_sloppak(
+        tmp_path,
+        manifest_extras={"drum_tab": "drum_tab.jsonc"},
+        side_files={"drum_tab.jsonc": text},
+    )
+    loaded = _load(pak, tmp_path)
+    assert loaded.drum_tab is not None
+    assert loaded.drum_tab["hits"][0]["p"] == "kick"
+
+
+# ── song_timeline .jsonc ─────────────────────────────────────────────────────
+
+def test_load_song_timeline_jsonc_with_comments(tmp_path: Path):
+    payload = {
+        "beats": [{"time": 0.0, "measure": 0}, {"time": 0.5, "measure": 0}],
+        "sections": [{"name": "intro", "number": 0, "time": 0.0}],
+    }
+    text = '/* timeline */\n' + json.dumps(payload)
+    pak = _write_sloppak(
+        tmp_path,
+        manifest_extras={"song_timeline": "song_timeline.jsonc"},
+        side_files={"song_timeline.jsonc": text},
+    )
+    loaded = _load(pak, tmp_path)
+    assert loaded.song_timeline is not None
+    assert len(loaded.song.beats) == 2
+    assert loaded.song.sections[0].name == "intro"
+
+
+# ── lyrics .jsonc ────────────────────────────────────────────────────────────
+
+def test_load_lyrics_jsonc_with_comments(tmp_path: Path):
+    payload = [
+        {"w": "Hel", "t": 0.0, "d": 0.2},
+        {"w": "lo", "t": 0.2, "d": 0.3},
+    ]
+    text = '// syllable lyrics\n' + json.dumps(payload)
+    pak = _write_sloppak(
+        tmp_path,
+        manifest_extras={"lyrics": "lyrics.jsonc"},
+        side_files={"lyrics.jsonc": text},
+    )
+    loaded = _load(pak, tmp_path)
+    assert len(loaded.song.lyrics) == 2
+    assert loaded.song.lyrics[0]["w"] == "Hel"
+
+
+# ── keys .jsonc ──────────────────────────────────────────────────────────────
+
+def test_load_keys_jsonc_with_comments(tmp_path: Path):
+    payload = {
+        "version": 1,
+        "events": [{"t": 0.0, "key": "Em", "scale": "natural_minor"}],
+    }
+    text = '/* key/scale track */\n' + json.dumps(payload)
+    pak = _write_sloppak(
+        tmp_path,
+        manifest_extras={"keys": "keys.jsonc"},
+        side_files={"keys.jsonc": text},
+    )
+    loaded = _load(pak, tmp_path)
+    assert loaded.keys is not None
+    assert loaded.keys["events"][0]["key"] == "Em"
+
+
+# ── Comment-like text inside strings is preserved end-to-end ─────────────────
+
+def test_load_arrangement_jsonc_preserves_comment_like_string_values(tmp_path: Path):
+    # A note whose fret label (if it had one) or a string field contains ``//``
+    # must survive the strip. We put a ``//`` inside the arrangement name and a
+    # ``/* */`` inside a beat section name to exercise both comment shapes.
+    arr_text = (
+        '{\n'
+        '  "name": "Lead // solo",\n'
+        '  "tuning": [0, 0, 0, 0, 0, 0], "capo": 0,\n'
+        '  "notes": [], "chords": [], "anchors": [], "handshapes": [], "templates": [],\n'
+        '  "beats": [],\n'
+        '  "sections": [{"name": "verse /* important */", "number": 0, "time": 0.0}]\n'
+        '}'
+    )
+    pak = _write_sloppak(
+        tmp_path,
+        manifest_extras={
+            "arrangements": [{"id": "lead", "name": "Lead",
+                              "file": "arrangements/lead.jsonc"}]
+        },
+        side_files={"arrangements/lead.jsonc": arr_text},
+    )
+    loaded = _load(pak, tmp_path)
+    arr = loaded.song.arrangements[0]
+    # The manifest's ``name: Lead`` overrides the arrangement JSON's name, so
+    # assert on the section name instead — it flows straight from the parsed
+    # .jsonc with no manifest override, proving the comment-like text inside
+    # the string survived the strip.
+    assert arr.name == "Lead"
+    assert loaded.song.sections[0].name == "verse /* important */"
+
+
+# ── lift_keys_notation reads .jsonc arrangements / song_timeline ─────────────
+
+def test_lift_keys_notation_loads_song_beats_from_jsonc_timeline(tmp_path: Path):
+    """``_load_song_beats`` (the helper the lifter uses to find downbeats) must
+    read a ``.jsonc`` song_timeline when the manifest points at one."""
+    timeline_text = (
+        '// timeline\n'
+        + json.dumps({
+            "beats": [{"time": 0.0, "measure": 0}, {"time": 0.5, "measure": 0},
+                      {"time": 1.0, "measure": 1}],
+            "sections": [],
+        })
+    )
+    pak = tmp_path / "song.sloppak"
+    pak.mkdir()
+    (pak / "arrangements").mkdir()
+    (pak / "arrangements" / "keys.json").write_text(json.dumps(_base_arrangement()))
+    (pak / "song_timeline.jsonc").write_text(timeline_text, encoding="utf-8")
+    manifest = {
+        "title": "T", "artist": "A", "duration": 4.0,
+        "arrangements": [{"id": "keys", "name": "Keys",
+                          "file": "arrangements/keys.json"}],
+        "song_timeline": "song_timeline.jsonc",
+        "stems": [{"id": "full", "file": "stems/full.ogg"}],
+    }
+    (pak / "manifest.yaml").write_text(yaml.safe_dump(manifest, sort_keys=False))
+    beats = _load_song_beats(pak, manifest)
+    assert len(beats) == 3
+    assert beats[2]["measure"] == 1
+
+
+def test_lift_keys_notation_falls_back_to_jsonc_arrangement_beats(tmp_path: Path):
+    """When no song_timeline is present, ``_load_song_beats`` falls back to the
+    first arrangement JSON carrying beats — and that arrangement may be ``.jsonc``."""
+    arr_text = (
+        '/* keys */\n'
+        + json.dumps({
+            **_base_arrangement(),
+            "beats": [{"time": 0.0, "measure": 0}, {"time": 1.0, "measure": 1}],
+        })
+    )
+    pak = tmp_path / "song.sloppak"
+    pak.mkdir()
+    (pak / "arrangements").mkdir()
+    (pak / "arrangements" / "keys.jsonc").write_text(arr_text, encoding="utf-8")
+    manifest = {
+        "title": "T", "artist": "A", "duration": 4.0,
+        "arrangements": [{"id": "keys", "name": "Keys",
+                          "file": "arrangements/keys.jsonc"}],
+        "stems": [{"id": "full", "file": "stems/full.ogg"}],
+    }
+    (pak / "manifest.yaml").write_text(yaml.safe_dump(manifest, sort_keys=False))
+    beats = _load_song_beats(pak, manifest)
+    assert len(beats) == 2
+    assert beats[1]["measure"] == 1