[zhuran24]

Summary

scripts/mutation-check.mjs mutated code outside the functions it was asked to focus on, never flipped && or ||, and could flip the wrong operator. This PR fixes the mutant collector and adds tests for it.

Related issue

None: issues are disabled on this repository.

Changes

collectMutations() had three defects:

1. Logical operators were never mutated. && and || are listed in BINARY_FLIPS, but acorn parses them as LogicalExpression, which had no visitor.
2. The wrong operator could be flipped. The mutant was built with original.replace(op, …), which changes the first occurrence of the operator text in the expression's source: inside a string literal ("===" === value became "!==" === value), inside a comment, or the inner + of (a + b) + c.
3. Focus ranges were guessed from text. inFocus() looked for a focus function's declaration in the 2000 characters before each node. Code after a focus function was mutated as if it were inside it, and the end of a focus function longer than 2000 characters was skipped.

The operator position now comes from acorn's token stream, and LogicalExpression gets the same visitor as BinaryExpression. Focus ranges are the source ranges of the named function declarations, function expressions and arrow functions in the AST, and an operator mutation is kept only when the operator itself lies in one of them. collectMutations() is exported, and main() runs only when the script is executed, directly or through a symlink, so test/mutation-check.test.js can import the collector.

Effect on the configured modules (dist/src built from main):

Module	Mutants on main	Of which outside the focus functions	Mutants with this PR	Of which on && / ||
cdp-eval	41	14	39	10
element-resolver	21	13	9	1
browser-runtime	19	0	39	19
helpers	19	10	13	4

The "outside" column counts mutants on main that fall in other functions, such as jsExceptionLocation and jsSnippet for cdp-eval, axNameMatches and isTextMatcher for element-resolver, and newTaskSpace and switchTaskSpace for helpers. With this PR every mutant falls inside a focus function. node scripts/mutation-check.mjs cdp-eval element-resolver runs end to end with the new collector: 39 of 48 mutants killed.

Verification

Run from package/ego-browser.

Check	main	This branch
npm test (build, typecheck, tests)	403 passed	411 passed
The 7 new collector tests against main's collector (exported, otherwise unchanged)	5 fail, 2 pass¹	7 pass
Starting the script through a symlink (new test)	n/a²	passes
prettier --check on the changed files	n/a	clean

¹ a missing focus function does not mutate unrelated code and function focus excludes an operator after a selected function expression already hold on main; they guard the new range check.
² On main the script calls main() unconditionally when loaded, so it cannot be imported by a test at all.

Impact

Development tooling only; npm run mutation-check reports on a different, intended set of mutants. No runtime, helper or CI change.

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