fix: copy .env file to build directory

[Sophmrs]

What's the purpose of this pull request?

The migration from Vercel to Homebrew of an account that uses NEXT_PUBLIC_* env vars failed as the builds in homebrew weren't inlining these env vars as expected.

How it works?

This PR adds a step during build to copy the .env from the source to the temporary .faststore directory, so that Nextjs can properly read the NEXT_PUBLIC_* env vars during build.

How to test it?

• Add a NEXT_PUBLIC env var in the store code: console.log('NEXT_PUBLIC_TEST_VALUE', process.env.NEXT_PUBLIC_TEST_VALUE)
• Create a .env file in the store with NEXT_PUBLIC_TEST_VALUE=test
• Run yarn build

  • Without this change, searching the built code for the variable, you can see the value was not inlined

  • With this change, you can see the value was inlined as expected

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References

Migration preventive incident (#inc-4855): https://vtex.enterprise.slack.com/archives/C0AB4N24R7A

Summary by CodeRabbit

• Bug Fixes
  • Fixed environment variable handling during builds: public NEXT_PUBLIC_* variables are now ensured to be present in the build temporary directory when a .env file exists, improving consistency of public env values during generate/build steps.
  • Reduces intermittent missing-public-variable issues across local and CI builds.

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[coderabbitai]

Walkthrough

Adds a public copyDotenv(basePath: string, tmpPath: string) to packages/cli/src/commands/build.ts and invokes it in Build.run after generation to copy an existing .env from the project base into the temporary build directory so NEXT_PUBLIC_* variables are available during the build.

Changes

Cohort / File(s)	Summary
Build Environment Variables packages/cli/src/commands/build.ts	Added exported copyDotenv(basePath, tmpPath) that copies .env from basePath to tmpPath if present (uses existsSync/copySync). Integrated a call to copyDotenv in Build.run after generate completes.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🌍 A .env file takes flight,
Copied to shadows where builds ignite,
Public secrets find their way,
Into NEXT_PUBLIC_* display,
Environment crafted, just right! 🚀

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: copying the .env file to the build directory to fix missing NEXT_PUBLIC_* environment variables during builds.

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✨ Finishing touches

• 📝 Generate docstrings

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