refactor(core): swap studio-api read path from recast to acorn parser (T6e)

[vanceingalls]

What

Swaps the GSAP read path in packages/core/src/studio-api/routes/files.ts from the recast-backed parseGsapScript to the browser-safe parseGsapScriptAcorn introduced in T6b (#1368).

Changed call sites (4):

• requireAnimation() helper — finds an animation by ID before a write op
• delete-all-for-selector case — enumerates animations for bulk delete
• GET /gsap-parse route — returns the parsed timeline to the studio UI
• POST /gsap-mutations response — re-parses after a mutation and returns the updated state

Not changed: the lazy loadGsapParser() for write ops. The acorn writer (gsapWriterAcorn.ts, T6c/#1369) covers the 8 standard GSAP ops, but four write ops used by files.ts are not yet ported: convertToKeyframesInScript, removeAllKeyframesFromScript, materializeKeyframesInScript, unrollDynamicAnimations. loadGsapParser stays until those are ported.

Why

gsapParser.ts transitively imports recast and @babel/parser, both of which call require("fs") and cannot bundle for the browser. The acorn parser was built to eliminate this constraint. T6b implemented it; T6c wired the write path for SDK ops; this PR completes the adoption by moving the studio-api read path off recast. Without this, recast stays live indefinitely despite a complete replacement existing.

Stack

• feat(lint): warn when composition is missing data-no-timeline #1338 feat(lint): warn when composition is missing data-no-timeline
• feat(core): acorn GSAP read path with T6b differential corpus tests #1368 feat(core): acorn GSAP read path — T6b
• feat(core): acorn GSAP write path — magic-string offset-splice (T6c) #1369 feat(core): acorn GSAP write path — T6c
• feat(core): parse-parity suite for acorn parser (T6d) #1370 feat(core): parse-parity suite — T6d
• feat(sdk,core): phase 3b — 8 gsap/label ops + setClassStyle #1379 feat(sdk,core): phase 3b — 8 GSAP/label ops + setClassStyle
• refactor(core): swap studio-api read path from recast to acorn parser (T6e) #1392 refactor(core): studio-api read path → acorn (this PR) — T6e

Test plan

• All 76 core test files pass (1567 tests)
• TypeScript build clean (bunx tsc --noEmit)
• Studio UI: open a composition, GSAP panel loads animations correctly
• Studio UI: mutate an animation (position, ease, duration) — response parses via acorn

[vanceingalls]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• refactor(core): swap studio-api read path from recast to acorn parser (T6e) #1392 👈 (View in Graphite)
• feat(sdk,core): phase 3b — 8 gsap/label ops + setClassStyle #1379
• feat(core): parse-parity suite for acorn parser (T6d) #1370
• feat(core): acorn GSAP write path — magic-string offset-splice (T6c) #1369
• feat(core): acorn GSAP read path with T6b differential corpus tests #1368
• main

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[miguel-heygen]

Clean mechanical swap of the four read-path call sites from parseGsapScript (recast-backed) to parseGsapScriptAcorn (browser-safe acorn). Both return the same ParsedGsap shape from gsapSerialize.ts, so the downstream consumers (requireAnimation, delete-all-for-selector, GET /gsap-parse, POST /gsap-mutations response) are unaffected structurally.

The loadGsapParser() update comment (files.ts:291–299) correctly documents why the lazy loader stays: the four write ops (convertToKeyframesInScript, removeAllKeyframesFromScript, materializeKeyframesInScript, unrollDynamicAnimations) are not yet ported to the acorn writer. The boundary is clean.

All CI green — all 8 regression shards pass, all Perf:* jobs pass, Preflight / Preview parity / player-perf pass.

Verdict: APPROVE
Reasoning: Diff is correct, minimal, and well-scoped. CI all-green confirms no behavioral regression from the parser swap.

— magi

[james-russo-rames-d-jusso]

hyperframes#1392 — refactor(core): swap studio-api read path from recast to acorn parser (T6e)

Looks good — cutover is clean, but two non-blocking gaps worth naming before this lands.

The diff is structurally tight: 4 call-site swaps in packages/core/src/studio-api/routes/files.ts (requireAnimation, delete-all-for-selector, GET /gsap-animations, POST /gsap-mutations re-parse). Recast stays loaded lazily for the 4 unported write ops (convertToKeyframesInScript, removeAllKeyframesFromScript, materializeKeyframesInScript, unrollDynamicAnimations) — appropriate boundary. The lint rule (packages/core/src/lint/rules/gsap.ts:174) intentionally continues to use recast since it's a server-side path; correct call.

The two correctness fixes folded into the swap commit (c0dcc1e) — lookupBindingFromAncestors program-scope fallback (gsapParserAcorn.ts:153-158) and fromTo arity guard (gsapParserAcorn.ts:475-499) — are well-targeted. The writer-side guards (valueToCode NaN→"0", safeKey ASCII regex tightening, removing the silent ID-rewrite fallback in removeAnimationFromScript) are also correct.

Concerns

• packages/core/src/parsers/gsapParser.stress.test.ts — the 947-line stress suite (unicode selectors, NaN/Infinity, ASI/malformed scripts, deeply nested staggers, template literals, etc.) still runs only against recast. The T6d parity suite (gsapParserAcorn.full.test.ts) covers basic shapes well, but doesn't replicate the stress-test corpus. At cutover, the acorn parser's behavior on those edge cases is uncovered by automated parity. Suggest a small follow-up (T6f?) that points the stress suite at acorn — or at minimum, confirm whether the regression-shards currently in flight exercise any of those input shapes against the new read path.

• No feature flag on the swap. If a parse-shape regression hits studio prod, the rollback is "revert + deploy", which is a multi-hour window. For a parser swap of this surface this is defensible — the parity suite is real coverage — but worth saying out loud: there is no instant-rollback. If you wanted to add one in a follow-up (HF_USE_ACORN_READ_PATH env-flag check at the 4 call sites), the cost is small and the optionality is real.

Nits

• packages/core/src/studio-api/routes/files.ts:454-455 — the executeGsapMutation destructure of parser no longer pulls parseGsapScript, but the variable name parser still suggests "the recast parser" to a reader. Optional rename to recastWriteOps would signal the shrinking surface. (nit)

• packages/core/src/parsers/gsapParserAcorn.full.test.ts:6-12 — trust-model header is a nice add. One tweak: the note "motionPath parity tests live in the Phase 3b commit (PR #1379)" reads correctly today, but once #1379 lands and the commit reference becomes stale, future readers will hunt for it. A pointer to the test file path (or the describe("motionPath parsing") block at line 925 of this same file after #1379 lands) would age better. (nit)

Questions

• What's the concrete plan to port the 4 remaining write ops off recast? Once done, loadGsapParser and the /gsap-parser subpath disappear entirely. Is there a T6f / T6g lined up, or is that out-of-scope for this workstream and recast stays parked indefinitely for those 4 ops?

What I didn't verify

• Whether the regression-shards (gsap-letters-render-compat, style-N-prod shards, etc.) currently in flight on this PR HEAD actually exercise the studio-api /gsap-animations and /gsap-mutations routes against real production-shape scripts. If they do, the stress-coverage concern above shrinks meaningfully. If they're render-only, it doesn't change.

• Behavioral parity on the very specific edge cases the stress suite covers — I did not hand-trace acorn output for malformed-ASI or unicode-selector scripts against recast baseline. The T6d full suite is what gives me confidence here, not a hand-check.

Cross-PR context I did verify

• motionPath gap from HF#1370 R2 does NOT propagate to this PR — #1379 (which adds the acorn motionPath parser AND its parity tests) is a downstack ancestor of #1392 in the Graphite stack. By the time T6e lands, motionPath is parity-tested.

• Empty-IR-on-parse-error behavior is identical between recast (gsapParser.ts:1123) and acorn (gsapParserAcorn.ts:1134) — both silent-catch and return { animations: [], timelineVar: "tl", preamble: "", postamble: "" }. No new behavioral divergence at the cutover. The /gsap-animations UI consumer will continue to show "no animations" on parse failure (pre-existing, not introduced here).

• No sibling test hardcodes a parser-name list that would break on the swap. No feature-flag default-flip lurking in the diff.

Review by Rames D Jusso

[jrusso1020]

LGTM.