Test: Fix missing source map for Webpack/Vite mock loaders and plugins

[valentinpalkovic]

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What I did

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  • bug: Internal changes that fixes incorrect behavior.
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Greptile Summary

This PR fixes missing source map generation for two Webpack loaders used in Storybook's mocking system. The changes modify both webpack-automock-loader.ts and storybook-mock-transform-loader.ts to return an object containing both transformed code and source maps, rather than just the code string.

In the webpack-automock-loader.ts, the change leverages the MagicString instance returned by getAutomockCode() to generate proper source maps using its built-in generateMap() method. The loader now returns { code: mocked.toString(), map: mocked.generateMap() } instead of just the string.

The storybook-mock-transform-loader.ts is similarly updated to return { code: result.code, map: result.map } from the rewriteSbMockImportCalls() function result. This aligns both loaders with the standard Webpack loader pattern of providing source maps for better debugging support.

These loaders are part of Storybook's core infrastructure for handling module mocking during development and testing. The source maps enable developers to debug their original code instead of seeing transformed/generated mock code in their debugger, significantly improving the developer experience when working with mocked modules.

PR Description Notes:

• The PR description is incomplete - the "What I did" section is empty and no testing approach is described
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Confidence score: 2/5

• This PR has a critical issue that could cause runtime errors in production
• The storybook-mock-transform-loader.ts assumes result.map exists, but the rewriteSbMockImportCalls() function may not generate source maps by default
• The storybook-mock-transform-loader.ts file needs careful review to ensure source maps are properly generated before being returned

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☁️ Nx Cloud last updated this comment at 2025-07-23 13:44:53 UTC

[storybook-app-bot]

Package Benchmarks

^{Commit: b914f50, ran on 23 July 2025 at 13:33:30 UTC}

The following packages have significant changes to their size or dependencies:

storybook

	Before	After	Difference
Dependency count	56	56	0
Self size	41.37 MB	41.35 MB	🎉 -15 KB 🎉
Dependency size	18.22 MB	18.22 MB	0 B
Bundle Size Analyzer	Link	Link

sb

	Before	After	Difference
Dependency count	57	57	0
Self size	1 KB	1 KB	0 B
Dependency size	59.59 MB	59.58 MB	🎉 -15 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/cli

	Before	After	Difference
Dependency count	221	221	0
Self size	584 KB	584 KB	0 B
Dependency size	103.99 MB	103.98 MB	🎉 -15 KB 🎉
Bundle Size Analyzer	Link	Link

@storybook/codemod

	Before	After	Difference
Dependency count	190	190	0
Self size	31 KB	31 KB	0 B
Dependency size	88.08 MB	88.07 MB	🎉 -15 KB 🎉
Bundle Size Analyzer	Link	Link