Fix Live Debugger parenthesized arrow body instrumentation#447
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When an expression-body arrow has a parenthesized body, the transform strips the wrapper parens before injecting the block body. It did this with MagicString `remove()`, which clears the chunk's intro/outro. If the body was itself an instrumented function whose end abutted the closing paren (e.g. `(a) => ((b) => a + b)`), the inner function had already appended its instrumentation suffix to that offset, so `remove()` dropped it and emitted invalid JavaScript. Blank the wrapper parens with `update(..., '')` instead. It edits content only and preserves the inner function's appended suffix. Also make the wrapper-paren scanner comment-aware. It previously counted raw `(`/`)` characters, so a paren inside a comment (e.g. `() => ((x) /* ) */)`) was mistaken for a wrapper paren, misaligning removal and again producing invalid JavaScript. Only whitespace, comments, and wrapper parens can appear in that range, so any `/` must start a comment and can be skipped. Add regression coverage for parenthesized inner arrows (nested, JSX, and object bodies) and comment/regex bodies, plus previously untested async functions and class accessors.
This was referenced Jul 3, 2026
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This was referenced Jul 3, 2026
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What and why?
This fixes two more cases where the Live Debugger transform emitted invalid JavaScript, both in the wrapper-paren removal path for parenthesized arrow expression bodies. They are the same family as the recently fixed nested-function bugs and were found by running the transform over a large battery of adversarial inputs and re-parsing every output.
The first case is a parenthesized arrow body wrapping an instrumented function whose end abuts the closing paren — e.g.
const f = (a) => ((b) => a + b);— which silently dropped the inner function's entire instrumentation suffix (return/catch/closing brace) and produced a syntax error. The second is a paren inside a comment within a parenthesized arrow body — e.g.const f = () => ((x) /* ) */);— which was mistaken for a wrapper paren and misaligned removal, again producing invalid output.How?
The transform strips wrapper parens before converting the arrow to a block body. It did this with MagicString
remove(), which clears the affected chunk'sintro/outro. When an inner instrumented function had alreadyappendRight-ed its suffix to that same offset (because the inner body abuts the closing paren with no whitespace), that suffix was discarded. This swapsremove()forupdate(pos, pos + 1, ''), which edits content only and preserves the appended suffix.It also replaces the two raw paren scanners with a single comment-aware
collectArrowWrapperParenshelper. Only whitespace, comments, and wrapper parens can appear between the outermost paren and the body, so any/there must start a comment; skipping//and/* */spans means parens inside comments are no longer miscounted as wrappers (regex/division cannot appear in that range, so no string/regex handling is needed).Tests add regression cases for parenthesized inner arrows (nested, double-parenthesized, JSX, and parenthesized-object bodies) and for comment/regex bodies, plus coverage for async functions and class accessors/static members, which previously had no transform-level tests. The full live-debugger unit suite passes (234 tests).