Core: Fix .env-file parsing

[JReinhold]

What I did

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

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• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

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  Available labels

  • bug: Internal changes that fixes incorrect behavior.
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  • dependencies: Upgrading (sometimes downgrading) dependencies.
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Summary by CodeRabbit

• Chores
  • Updated environment variable configuration during the build process for improved consistency and maintainability.

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[coderabbitai]

Caution

Review failed

The pull request is closed.

📝 Walkthrough

Walkthrough

Injects an explicit 'process.env' object into DefinePlugin in the webpack preview config and refactors env utilities to build a single consolidated raw env from base defaults, dotenv/process.env merge, filtered STORYBOOK_ entries, and normalized NODE_PATH, with simplified stringification.

Changes

Cohort / File(s)	Summary
Webpack preview DefinePlugin change code/builders/builder-webpack5/src/preview/iframe-webpack.config.ts	Adds a DefinePlugin option entry 'process.env': (${JSON.stringify(envs)}) alongside existing serialized env mappings, explicitly injecting the entire envs object under process.env.
Environment utilities refactor code/core/src/common/utils/envs.ts	Replaces multi-step env construction with baseEnv, merges dotenv/process.env via getEnvironment(...), extracts STORYBOOK_ keys into envEntries, composes a single raw (base + envEntries), normalizes NODE_PATH with nodePathsToArray, and derives stringified directly from raw; removes fullRaw and prior process.env workaround.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

• Verify merge order and precedence between baseEnv, dotenv (getEnvironment(...)), and process.env.
• Confirm STORYBOOK_ key filtering produces the expected keys/values in raw.
• Check NODE_PATH normalization and any module resolution implications.
• Ensure the added 'process.env' DefinePlugin entry doesn't conflict with other DefinePlugin entries or runtime assumptions.

✨ Finishing touches

• 📝 Generate docstrings

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📜 Recent review details

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📥 Commits

Reviewing files that changed from the base of the PR and between 3d9a2a5 and 1cbf505.

📒 Files selected for processing (2)

• code/builders/builder-webpack5/src/preview/iframe-webpack.config.ts (1 hunks)
• code/core/src/common/utils/envs.ts (2 hunks)

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