refactor: validate options from webpack's validate hook

[alexander-akait]

Summary

Moves option validation out of the constructor and onto compiler.validate, called from compiler.hooks.validate, so webpack owns when validation runs. validate: false now actually skips it — the constructor validated whatever the config said — and the schema is required lazily by the callback rather than at module load. Handing compiler.validate a pre-compiled check, so schema-utils and ajv are not loaded for valid options, is left to a follow-up PR.

Two fallbacks, both marked TODO to remove in the next major release:

• webpack calls hooks.validate before it applies optimization.minimizer, so that hook reaches this plugin only where it sits in plugins. initialize is tapped alongside it, behind a latch, so the minimizer placement is validated too.
• webpack before 5.106 has neither the hook nor compiler.validate, and validates with schema-utils directly.

Measured against a real webpack build, n=7 per arm, medians with ranges; retained heap read after forced GC:

	before	after
require() the plugin	6.1 ms	3.2 ms
default setup	404 ms [389-482]	419 ms [390-446]
default ajv modules / require.cache / retained heap	126 / 770 / 25.5 MB	126 / 770 / 25.5 MB
validate: false setup	429 ms [411-439]	298 ms [292-328]
validate: false ajv modules / require.cache / retained heap	126 / 770 / 25.4 MB	0 / 590 / 22.4 MB

Requiring the plugin is faster because options.json is no longer parsed at module load. With validation on nothing else moves: the default-setup difference is smaller than the run-to-run spread and the ranges overlap, so it is not a result, and ajv loads either way until the pre-compiled check lands. The win is validate: false, where the ranges are disjoint.

What kind of change does this PR introduce?

refactor

Did you add tests for your changes?

Yes — test/validate-options.test.js drives real compilers throughout, and adds a case for the optimization.minimizer placement. No unit tests: the pre-5.106 schema-utils fallback is therefore not covered by any test, since the matrix only runs webpack-version: latest.

Does this PR introduce a breaking change?

No. Invalid options are still rejected with the same message; the error is now thrown when the compiler is created rather than when the plugin is constructed, and validate: false now suppresses it.

If relevant, what needs to be documented once your changes are merged or what have you already documented?

n/a

Use of AI

Claude Code was used to rewire the validation and update the tests. The hook-ordering claim was verified empirically against webpack 5.109.2 rather than assumed: a probe plugin tapping both hooks reports validate, initialize for the plugins placement and initialize only for optimization.minimizer. The measurements above were taken by counting loaded modules and timing a real build across both arms; an earlier version of the harness attributed the constructor's cost to the wrong phase and was corrected before these numbers were taken. All changes were reviewed before committing.

[changeset-bot]

🦋 Changeset detected

Latest commit: 2adc2f6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
minimizer-webpack-plugin	Minor

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[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.39%. Comparing base (202428d) to head (2adc2f6).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/index.js	90.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #701      +/-   ##
==========================================
- Coverage   89.43%   89.39%   -0.05%     
==========================================
  Files           3        3              
  Lines         729      745      +16     
  Branches      251      259       +8     
==========================================
+ Hits          652      666      +14     
- Misses         66       68       +2     
  Partials       11       11              

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