fix(stream): honor PassThrough subclass transforms

[proggeramlug]

Summary

• recognize PassThrough as a native node:stream parent in class declarations and class expressions
• initialize derived instances through a dedicated PassThrough subclass helper, preserving _transform overrides and default identity behavior
• cover direct, aliased, dynamic, indirect, and default PassThrough inheritance paths

Fixes #10745.

Validation

• focused HIR lowering test passes
• focused runtime subclass initializer test passes
• Node 26.5.1 and Perry output match byte for byte for direct import, renamed import, class expression alias, indirect subclass, and default identity cases
• cargo fmt --all -- --check
• git diff --check
• scripts/check_file_size.sh
• python3 scripts/raw_handle_debt.py --check

Summary by CodeRabbit

• New Features

  • Added support for subclassing node:stream’s PassThrough across direct, aliased, dynamic, and indirect inheritance.
  • PassThrough subclasses now honor custom _transform implementations.
  • Subclasses without an override retain PassThrough’s default identity-transform behavior.

• Bug Fixes

  • Prevented PassThrough subclass initialization from falling through to incorrect stream handling.

• Tests

  • Added coverage for inheritance patterns and custom or default transform behavior.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: 811bde6a-00e6-4d5a-ad86-4e7efdcd923e

📥 Commits

Reviewing files that changed from the base of the PR and between f5cfbff and 6cebdbf.

📒 Files selected for processing (18)

• changelog.d/11028-passthrough-subclass.md
• crates/perry-codegen/src/codegen/helpers.rs
• crates/perry-codegen/src/codegen/method.rs
• crates/perry-codegen/src/expr/this_super_call.rs
• crates/perry-codegen/src/expr/write_barrier.rs
• crates/perry-codegen/src/lower_call/new.rs
• crates/perry-codegen/src/lower_call/new_helpers.rs
• crates/perry-codegen/src/runtime_decls/stdlib_ffi/streams_events.rs
• crates/perry-hir/src/lower/tests.rs
• crates/perry-hir/src/lower/tests/issue_10745_passthrough_heritage.rs
• crates/perry-hir/src/lower_decl/class_decl.rs
• crates/perry-hir/src/lower_decl/class_decl/from_ast.rs
• crates/perry-runtime/src/node_stream_constructors.rs
• crates/perry-runtime/src/node_stream_constructors/builders.rs
• crates/perry-runtime/src/node_stream_keepalive.rs
• crates/perry-runtime/src/node_stream_state_tests.rs
• crates/perry-runtime/src/object/global_this/fetch_globals.rs
• test-files/test_gap_10745_passthrough_subclass.ts

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📝 Walkthrough

Walkthrough

PassThrough is now recognized as a native node:stream parent. Constructor and super() paths dispatch to a dedicated runtime initializer. The initializer preserves subclass _transform callbacks and applies identity behavior when no override exists. Tests cover multiple inheritance forms.

Changes

PassThrough stream subclass support

Layer / File(s)	Summary
Recognize PassThrough heritage crates/perry-hir/src/lower_decl/*, crates/perry-hir/src/lower/tests/*	HIR class lowering recognizes PassThrough bindings as native node:stream parents for declaration and expression classes.
Route PassThrough construction crates/perry-codegen/src/codegen/*, crates/perry-codegen/src/expr/*, crates/perry-codegen/src/lower_call/*, crates/perry-codegen/src/runtime_decls/stdlib_ffi/streams_events.rs	Code generation maps PassThrough to the passthrough kind and dispatches constructor, spread-super, fixed-arity-super, and inline-super paths to js_node_stream_passthrough_subclass_init.
Initialize PassThrough subclasses crates/perry-runtime/src/node_stream_constructors/*, crates/perry-runtime/src/node_stream_keepalive.rs, crates/perry-runtime/src/object/global_this/fetch_globals.rs, crates/perry-runtime/src/node_stream_state_tests.rs	The runtime initializer uses Transform setup, preserves a subclass _transform callback, applies the hidden identity marker when no callback exists, supports dynamic superclass dispatch, and retains the entry point during linking.
Validate inheritance shapes test-files/test_gap_10745_passthrough_subclass.ts, changelog.d/11028-passthrough-subclass.md	The integration test covers direct, aliased, local, indirect, expression, and default PassThrough subclasses. The changelog records override and identity behavior.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix · Severity of issue fixed: Medium

Sequence Diagram(s)

sequenceDiagram
  participant Subclass
  participant HIR
  participant Codegen
  participant Runtime
  Subclass->>HIR: extend PassThrough
  HIR->>Codegen: record native node_stream parent
  Codegen->>Runtime: invoke js_node_stream_passthrough_subclass_init
  Runtime->>Runtime: install _transform override or identity marker
  Runtime-->>Subclass: return initialized PassThrough instance

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Merge Risk: ⚪ Minimal · up to 6cebd

The PassThrough initializer is retained in keepalive builds, and default subclass behavior is compared with Node output. No concrete merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 63.16% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 19 functions across 17 files. (1 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: preserving transforms on PassThrough subclasses.
Description check	✅ Passed	The description explains the fix, lists the main implementation areas, references issue #10745, and provides focused validation details. It does not use every template heading or checklist item, but i…
Linked Issues check	✅ Passed	Issue #10745 requires HIR recognition of PassThrough as a native node:stream parent and hidden-field initialization for _transform overrides. At the reviewed head, HIR recognizes direct and alia…
Out of Scope Changes check	✅ Passed	The changes remain within Issue #10745. The code changes implement native-parent recognition, codegen dispatch, FFI retention, runtime initialization, and focused HIR/runtime regression tests. The cha…

Full details: Docstring Coverage

Explanation

Docstring coverage is 63.16% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 19 functions across 17 files. (1 skipped: 1 unsupported.)

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[proggeramlug]

Landed on main in merge train 260 (#11085), released as v0.5.1643 at d8f24f15ed.

Cherry-picked from this PR's head 6cebdbfa2e and validated as one tree — CI 22/22 green, all 6 gap-suite shards. A train rebase gives the commits new SHAs, so GitHub cannot auto-close the source PR; closing by hand.

Nothing needed from you. Thanks.