fix: restrict UOI mutations to identifier primaries only

[SamanAttar]

Explain Your Changes

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The UOI mutator was generating mutations for primary expressions that are not valid assignment targets. Specifically literals (42, 'hello', true, null), this, super, SOQL/SOSL queries, type references, void, and expressions used as the receiver of a dot or safe-navigation expression (e.g. foo.bar).

Instead of maintaining an ad-hoc denylist of non-assignable text patterns, this will help simplify the mutator but using an allowlist: it only generates mutations when the primary child is an IdPrimaryContext (a plain identifier like x or myVar). All other primary types are rejected by construction.

The DotExpressionContext parent check is added to guard against dot-receiver positions that would also produce invalid mutations as an early exit.

The isLiteral private helper has been removed as it is no longer needed.

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closes #126

• Unit tests added to cover the fix.
• NUT tests added to cover the fix.
• E2E tests added to cover the fix.

Any particular element that can be tested locally

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Any other comments

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[github-actions]

Performance Comparison (same runner)

Regressions

Benchmark	Base	PR	Ratio	Change
antlr-parse-small	123	84	1.46	-46.4%
antlr-parse-medium	26	17	1.53	-52.9%
antlr-parse-medium (mean)	37.9428ms	59.8873ms	1.58	+57.8%

Stable

Benchmark	Base	PR	Ratio	Change
antlr-lex-small	6927	6817	1.02	-1.6%
antlr-lex-medium	1464	1426	1.03	-2.7%
antlr-lex-large	461	449	1.03	-2.7%
antlr-parse-large	9	9	1.00	+0%
pipeline-small-compute-mutations	117	101	1.16	-15.8%
pipeline-small-type-discovery	172	157	1.10	-9.6%
pipeline-medium-compute-mutations	29	26	1.12	-11.5%
pipeline-medium-type-discovery	36	33	1.09	-9.1%
pipeline-large-compute-mutations	10	9	1.11	-11.1%
pipeline-large-type-discovery	12	11	1.09	-9.1%
pipeline-apply-all-mutations	3	3	1.00	+0%
antlr-lex-small (mean)	0.1444ms	0.1467ms	1.02	+1.6%
antlr-parse-small (mean)	8.1599ms	11.9096ms	1.46	+46.0%
antlr-lex-medium (mean)	0.6829ms	0.701ms	1.03	+2.7%
antlr-lex-large (mean)	2.1697ms	2.2251ms	1.03	+2.6%
antlr-parse-large (mean)	108.7301ms	116.0726ms	1.07	+6.8%
pipeline-small-compute-mutations (mean)	8.5776ms	9.859ms	1.15	+14.9%
pipeline-small-type-discovery (mean)	5.8024ms	6.3627ms	1.10	+9.7%
pipeline-medium-compute-mutations (mean)	34.7654ms	38.1791ms	1.10	+9.8%
pipeline-medium-type-discovery (mean)	27.5057ms	30.2796ms	1.10	+10.1%
pipeline-large-compute-mutations (mean)	100.6786ms	108.8506ms	1.08	+8.1%
pipeline-large-type-discovery (mean)	81.82ms	88.1229ms	1.08	+7.7%
pipeline-apply-all-mutations (mean)	332.731ms	321.2675ms	0.97	-3.4%

[scolladon]

LGTM

Nice finding, thanks

[scolladon]

LGTM

[github-actions]

Published under dev-pr-127 draft release.

sf plugins install https://github.com/scolladon/apex-mutation-testing/releases/download/dev-pr-127/apex-mutation-testing-dev-pr-127.tgz

[github-actions]

Shipped in release v1.7.1.
Version v1.7.1 will be assigned to the latest npm channel soon
Install it using either v1.7.1 or the latest-rc npm channel

$ sf plugins install apex-mutation-testing@latest-rc
# Or
$ sf plugins install apex-mutation-testing@v1.7.1

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