fix(runtime): stringify ArrayBuffer views with object tags

[proggeramlug]

Fixes #10927.

js_jsvalue_to_string treated every registered BufferHeader as a Node Buffer and decoded its bytes. ArrayBuffer, SharedArrayBuffer, and DataView use that storage too, but inherit Object.prototype.toString. Route those three through the existing object-tag implementation before any GC-header probe. Apply the same distinction in the argument-bearing toString helpers so .toString("hex") cannot decode their bytes.

The regression fixture covers String(value), template interpolation, .toString(), and .toString("hex") for all three views, plus Node Buffer decoding. Against the pre-fix compiler, the fixture prints "hi" for each view; pinned Node 26.5.1 prints their object tags.

Validation: cargo fmt --all --check; ./scripts/check_file_size.sh; python3 scripts/check_test_registration.py; cargo test -p perry-runtime --lib array_buffer_backed_values_use_their_object_tags -- --test-threads=1 (passed). The new fixture was compiled and run with this branch’s release compiler and runtime archive on an isolated perrymaster checkout; its output matched pinned Node 26.5.1 byte for byte. The pre-fix compiler rendered "hi" for all three views.

Summary by CodeRabbit

• Bug Fixes
  • Corrected string conversion for ArrayBuffer, SharedArrayBuffer, and DataView values to return their standard object tags.
  • Ensured template interpolation and .toString() produce consistent results for these values.
  • Preserved byte decoding behavior for Node.js Buffer instances, including hexadecimal conversion.

CI note: the lint job on the initial push also failed benchmarks/ci_public_baseline_check.py with a public artifact source-fingerprint mismatch. This PR changes none of SOURCE_PATHS or the artifact in benchmarks/public_baseline.py; the same mismatch is present at its upstream/main base. The new file-size violation from the first push has been fixed, and the file-size gate passes locally.

[coderabbitai]

Navigate logical layers of code changes, visualize relationships, and explore their blast radius.

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: 704598aa-b92d-4d2c-80e4-9e9be79735d6

📥 Commits

Reviewing files that changed from the base of the PR and between eb84d76 and b01576c.

📒 Files selected for processing (3)

• crates/perry-runtime/src/value/mod.rs
• crates/perry-runtime/src/value/to_string.rs
• crates/perry-runtime/src/value/to_string_buffer_tests.rs

Included review availability: Your plan provides up to 8 included reviews per hour; 0 remain after this review.

---

📝 Walkthrough

Walkthrough

ArrayBuffer, SharedArrayBuffer, and DataView string conversion now returns branded object tags. Byte-indexed Buffer values still decode their contents. Runtime tests, an integration test, and a changelog entry cover the behavior.

Changes

Buffer string conversion

Layer / File(s)	Summary
Runtime routing and validation crates/perry-runtime/src/buffer/encode.rs, crates/perry-runtime/src/value/to_string.rs, crates/perry-runtime/src/value/mod.rs, crates/perry-runtime/src/value/to_string_buffer_tests.rs	String conversion dispatch recognizes byte-indexed buffers and preserves byte decoding for Buffer. Runtime tests verify branded object tags for ArrayBuffer, SharedArrayBuffer, and DataView, plus plain and hexadecimal Buffer conversion.
Integration regression coverage test-files/test_gap_10927_arraybuffer_string.ts, changelog.d/10966-arraybuffer-string.md	The integration test covers String(), template interpolation, .toString(), and encoded conversion. The changelog records the corrected behavior.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to b0157

This change corrects string conversion for ArrayBuffer-backed values while preserving Buffer decoding. No actionable merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 57.14% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Issue #10927 requires object-tag conversion for ArrayBuffer and SharedArrayBuffer, matching template interpolation, and unchanged Node Buffer decoding. js_value_to_string_with_encoding and its…
Out of Scope Changes check	✅ Passed	The changes stay within issue #10927. DataView uses the same non-byte-indexed buffer classification and prevents the same incorrect byte decoding. The argument-bearing dispatch update supports the r…
Title check	✅ Passed	The title clearly and concisely describes the main runtime change: stringifying ArrayBuffer views with object tags.
Description check	✅ Passed	The description explains the bug, implementation, affected values, regression coverage, related issue, validation commands, and CI context. It does not reproduce the template headings or checklist, bu…

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create a new PR

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[proggeramlug]

Landed on main in merge train 256 (#11018, v0.5.1638), main f5cfbff882.

Carried at head b01576c60d. The landed tree is byte-identical to the validated train tree (9b108dd3c9), and CI on the train head passed every job except the known public-baseline lint step: all 6 gap shards, cargo-test, e2e-scoped, gc-stress, check, warnings and security-audit green.

Trains rebase-merge, so commits get new SHAs and GitHub cannot mark this PR merged. Closed as landed.