fix(hir): dispatch Array-mutator-named methods on any-typed receivers by runtime shape (#5139)

[proggeramlug]

Summary

Fixes #5139 — react-dom/server's renderToStaticMarkup returned an empty string instead of the rendered HTML when react-dom is compiled natively via perry.compilePackages.

Root cause

The bug was in HIR lowering, not in react-dom. The Fizz SSR renderer accumulates output by calling destination.push(chunk) on a plain-object sink:

const destination = { push(chunk) { result += chunk } };
// …flows through several any-typed params…
function writeChunk(d, chunk) { return d.push(chunk); } // d : any

HIR lowering eagerly rewrote recv.push(x) — where recv is statically any — into the array-only fast path (Expr::ArrayPush / the array.push_single native arm). That path reads the receiver's header as an ArrayHeader, so the plain object's bytes were interpreted as array length/capacity: push returned a bogus numeric length and the user closure never ran, dropping every chunk — SSR yielded "".

This affected any object owning a method whose name collides with an Array.prototype mutator (push/pop/shift/unshift/splice/sort/reverse/concat) when invoked through an any-typed receiver.

Fix

The two lowering sites — local_array_methods.rs (bare-ident receivers) and array_only_methods.rs (the fallback for arbitrary expressions) — now defer those mutator names to the runtime js_native_call_method dispatch when the receiver's static type is unknown/any. That dispatcher already selects by runtime shape:

• real array → dense js_array_* helpers (growth still resolves via the Array.push from inside an async function silently caps at 16 elements when the array is a function parameter #233 forwarding pointer, so realloc across a call boundary is preserved);
• plain object with an own callable of that name → invokes it with this bound to the receiver (via try_object_arraylike_mutator's own-user-method gate + the generic own-field scan).

Positively array-typed receivers keep the inline fast path unchanged, and the read-only iteration folds (map/filter/entries/…) on any receivers are untouched.

Verification

• Reproduced against the real react-dom@18.3.1 package compiled via perry.compilePackages. The issue's repro now prints, matching Node:

  <ul id="L"><li>item-1</li><li>item-2</li><li>item-3</li></ul>
  

• New regression tests in crates/perry/tests/issue_5139_object_arraylike_method_dispatch.rs:
  • object push closure runs when invoked through any-typed params (the reduced Fizz flush loop);
  • all eight mutator-named own methods dispatch to the object's closures;
  • any-typed real arrays keep Array.prototype semantics, including 1000-push growth across a function boundary, unshift/push/reverse/splice, comparator sort, and in-place pop/shift.
• Full perry integration suite + perry-runtime unit tests (1035) pass, plus perry-hir/perry-codegen tests — no regressions.

No version bump or CHANGELOG entry (left to maintainer at merge).

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Fixed method dispatch for objects with unknown types to correctly invoke custom methods instead of incorrectly treating them as arrays; resolves issue #5139 affecting react-dom/server's renderToStaticMarkup.

• Tests

  • Added regression tests verifying proper method dispatch for plain objects, array mutators on objects, and real arrays with correct semantics.

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

Two guards are added to the HIR lowering passes (array_only_methods and local_array_methods) to bail out of the array fast-path when the receiver's static type is None, Any, or Unknown for array-mutator method names. A new regression test file adds three end-to-end tests covering plain-object dispatch, all mutator names, and real arrays stored in any.

Changes

Array-mutator dispatch fix for any/unknown receivers

Layer / File(s)	Summary
HIR lowering guards for unknown receiver types crates/perry-hir/src/lower/expr_call/local_array_methods.rs, crates/perry-hir/src/lower/expr_call/array_only_methods.rs	is_arraylike_mutator_method predicate added; is_not_string routing updated to skip the array block for unknown receivers; try_array_only_methods gains an early Err(args) bail-out for None/Any/Unknown receiver types on the eight mutator method names.
Regression tests for issue #5139 crates/perry/tests/issue_5139_object_arraylike_method_dispatch.rs	Adds perry_bin() and compile_and_run() helpers plus three tests: (1) plain-object push closure via any, (2) all mutator names dispatching to object closures, (3) real arrays in any preserving standard mutator semantics.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly related issues

• compilePackages: react-dom/server renderToStaticMarkup returns empty string #5139: This PR directly implements the fix for the reported dispatch bug where array-mutator method calls on any/unknown-typed receivers were incorrectly folded into the HIR array fast-path instead of dispatching to the object's own closure properties.

Poem

🐇 A bunny once hopped through the any-typed land,
Where push on an object was misunderstood, unplanned.
"That's not an array!" cried the guard with a leap,
Now the type-check defers, no false fast-path to keep.
Plain objects and arrays each follow their own—
The correct method found, wherever they roam! 🌿

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	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 specifically summarizes the main fix: dispatching array-mutator methods on any-typed receivers by runtime shape, directly addressing issue #5139.
Description check	✅ Passed	The description fully covers the template requirements with clear Summary, Changes, Related issue (#5139), and comprehensive Test plan demonstrating verification against real react-dom package and new regression tests.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/5139-renderToStaticMarkup

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