fix(url): String/template/concat of URL & URLSearchParams give href/query (Node parity)

[proggeramlug]

Problem

ToString coercion of a WHATWG URL / URLSearchParams returned [object Object], diverging from explicit url.toString() (which already works):

                    # node v26.3.0          # perry (before)
url.toString()    → https://e.com/p?x=1   https://e.com/p?x=1   ✓
String(url)       → https://e.com/p?x=1   [object Object]       ✗
`${url}`          → https://e.com/p?x=1   [object Object]       ✗
"" + url          → https://e.com/p?x=1   [object Object]       ✗
String(usp)       → a=1&b=2               [object Object]       ✗
`${usp}`          → a=1&b=2               [object Object]       ✗

URL/URLSearchParams carry native toStrings (the href / the query string) that aren't discoverable as object fields, so the generic OrdinaryToPrimitive resolves the inherited Object.prototype.toString → [object Object].

Fix

Two coercion entry points needed a URL/URLSearchParams arm, mirroring the existing Date special-cases:

• js_jsvalue_to_string (backs String(x) / explicit coercion): detect URL/USP before OrdinaryToPrimitive and return the href / query string. The pointer is normalized to POINTER_TAG first since the operand can arrive as a raw heap pointer (upper-16 == 0).
• to_primitive_default_for_add (backs + and template literals via js_dynamic_string_or_number_add): same arm before ordinary_to_primitive_number_for_add, which would otherwise return the inherited Object.prototype.toString's [object Object].

Reuses existing js_url_href_if_url / try_read_as_search_params detectors and js_url_search_params_to_string.

Verification (vs Node v26.3.0)

• explicit / String() / template / concat of a URL → href; of a URLSearchParams → query string. ✓
• No regression: custom toString/valueOf/plain-object/class coercion unchanged (CUSTOM/T/C/pt, and [object Object] for valueOf-only & plain). ✓
• The full URL differential probe (href/origin/host/searchParams/relative resolution/sort/encode/etc.) is byte-identical to Node.
• perry-runtime to_string + dynamic + concat unit tests pass. (builtin_prototype_methods_reject_dynamic_new passes in isolation; its failure under the parallel dynamic filter is pre-existing test-interference, not this change.)

Found via a node --experimental-strip-types differential sweep; relates to the parity roadmap (#4315). No version bump / changelog per maintainer instruction.

Summary by CodeRabbit

• Bug Fixes
  • Improved coercion behavior so String(url) now stringifies URL objects to their href value.
  • Improved coercion behavior so URLSearchParams objects now stringify to their serialized query-string form.
  • Enhanced numeric/arithmetic conversions for URL/URLSearchParams to better match native URL/URLSearchParams behavior.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

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Run ID: cf62b5ed-9144-4d8b-a531-5451052417fa

📥 Commits

Reviewing files that changed from the base of the PR and between 4dd77d2 and a474806.

📒 Files selected for processing (2)

• crates/perry-runtime/src/value/dynamic_arith.rs
• crates/perry-runtime/src/value/to_string.rs

🚧 Files skipped from review as they are similar to previous changes (2)

• crates/perry-runtime/src/value/to_string.rs
• crates/perry-runtime/src/value/dynamic_arith.rs

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📝 Walkthrough

Walkthrough

Two coercion functions gain early URL/URLSearchParams detection: to_primitive_default_for_add in dynamic_arith.rs and js_jsvalue_to_string in to_string.rs. Both box the raw heap pointer, check for URL via js_url_href_if_url, fall back to try_read_as_search_params for URLSearchParams, and return the appropriate string before reaching the existing OrdinaryToPrimitive path.

Changes

URL/URLSearchParams Coercion Fix

Layer / File(s)	Summary
URL/URLSearchParams early-exit in + and toString coercion crates/perry-runtime/src/value/dynamic_arith.rs, crates/perry-runtime/src/value/to_string.rs	Both to_primitive_default_for_add and js_jsvalue_to_string now box the heap pointer, call js_url_href_if_url for URL objects and try_read_as_search_params for URLSearchParams, and return the serialized string before falling through to OrdinaryToPrimitive.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐇 A URL hops into a string,
No [object Object] — what a thing!
The href returns, the query streams,
Coercion now does what it seems.
Warren rejoices, specs align!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main fix: enabling proper string coercion for URL and URLSearchParams objects to return href/query instead of [object Object], achieving Node.js parity.
Description check	✅ Passed	The description provides comprehensive context including the problem statement, root cause analysis, the specific fix implemented in two functions, verification results, and test coverage information.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
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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