fix: preserve compiler paths for shared plugin instances

[utkarshalpha]

Summary

Fixes #506.

A BundleAnalyzerPlugin instance can be applied to multiple compilers, but the plugin previously stored only the most recently applied compiler. As a result, every done-hook callback resolved bundle assets and report files against that compiler's output directory.

This change:

• passes the compiler captured by each done-hook closure into report and stats generation;
• resolves bundle directories and output filenames against that compiler;
• uses the current compiler's bundle directory when refreshing server-mode chart data; and
• adds a multi-compiler regression test with one shared plugin instance for both Webpack 4 and Webpack 5.

Testing

• npm exec -- jest test/plugin.js --runInBand --testNamePattern=should.use.each.compiler.output.path (2 passed)
• npm exec -- jest test/viewer.js --runInBand (5 passed)
• npm exec -- eslint src/BundleAnalyzerPlugin.js src/viewer.js test/plugin.js
• npm exec -- tsc --pretty --noEmit
• npm exec -- prettier --check src/BundleAnalyzerPlugin.js src/viewer.js test/plugin.js .changeset/calm-compilers-report.md
• npm run build

[changeset-bot]

🦋 Changeset detected

Latest commit: 8fabe1a

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

This PR includes changesets to release 1 package

Name	Type
webpack-bundle-analyzer	Patch

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[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: utkarshalpha / name: Utkarsh Tiwari (268ab53)

[valscion]

Is there a reason to allow leaving out the compiler argument now? This looks like AI using protective coding pattern over understanding if this default is what we want or not.

[utkarshalpha]

Good catch — there was no real need for the default. The hook already threads the actual compiler through every internal call site, so I removed the this.compiler fallback and made the parameter required in 8fabe1a.

[codecov]

Codecov Report

❌ Patch coverage is 53.33333% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.29%. Comparing base (97d2ef8) to head (8fabe1a).

Files with missing lines	Patch %	Lines
src/BundleAnalyzerPlugin.js	61.53%	5 Missing ⚠️
src/viewer.js	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #725   +/-   ##
=======================================
  Coverage   76.29%   76.29%           
=======================================
  Files          17       17           
  Lines         983      983           
  Branches      357      358    +1     
=======================================
  Hits          750      750           
  Misses        206      206           
  Partials       27       27           

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[valscion]

Looks good to me!

Also, noticed that analyzerMode === "server" is not really covered even in base branch so those changed lines also can't be verified by CI... would be lovely to see a change that would add missing coverage for that.