feat: Add .env.<codebase> support for multi-instance functions

[taeold]

Summary

Adds support for .env.<codebase> environment files as an enhancement to the multi-instance functions feature from #8911.

This enables per-codebase environment variable isolation by adding .env.<codebase> to the environment file loading precedence.

Environment File Precedence (Updated)

1. .env (global defaults)
2. .env.<codebase> (codebase-specific) ← NEW
3. .env.<project|alias> (project overrides)
4. .env.local (emulator only)

Changes

• Updated UserEnvsOpts interface to include required codebase parameter
• Modified findEnvfiles() to load .env.<codebase> files in correct precedence order
• Added unit tests for codebase environment variable functionality
• Updated all callers to pass codebase parameter

Related

This builds on the multi-instance functions implementation in #8911 by adding the environment variable isolation component described in the original design spec.

[gemini-code-assist]

Summary of Changes

Hello @taeold, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the multi-instance functions feature by introducing support for codebase-specific environment variables through .env.<codebase> files. This allows developers to define distinct environment configurations for different function codebases, even if they share the same source directory. Additionally, it adds the ability to specify a prefix for function names, ensuring uniqueness and better organization when deploying multiple instances of functions from a single source. These changes improve environment isolation and naming flexibility for complex function deployments.

Highlights

• Codebase-Specific Environment Variables: Introduced support for .env.<codebase> files, allowing environment variables to be isolated and configured per codebase in multi-instance functions.
• Environment File Precedence: Updated the environment variable loading precedence to prioritize .env.<codebase> files over global .env files, but still allow .env.<project|alias> and .env.local (for emulators) to override them.
• Function Naming with Prefixes: Added a new prefix property to function configurations, enabling unique naming for functions that share the same source code across different codebases.
• Configuration Validation: Implemented validation for the new prefix property, ensuring it adheres to naming conventions and that source-prefix pairs are unique.
• Emulator Support: Extended the Functions Emulator to correctly handle and apply codebase-specific environment variables and function prefixes during local development and testing.

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[gemini-code-assist]

Code Review

This pull request introduces support for .env.<codebase> environment files and function name prefixes, enhancing multi-instance function capabilities. The changes are well-implemented across configuration, deployment, and emulation, with thorough test coverage. My review identified a type-related bug in the emulator's prefix handling logic that could cause runtime issues. I've provided a fix and also suggested refactoring some duplicated code to improve maintainability. Overall, this is a solid contribution.

[taeold]

/gemini review

[gemini-code-assist]

Code Review

This pull request adds support for codebase-specific environment files (.env.<codebase>), which is a great enhancement for managing multi-instance functions. The implementation correctly adjusts the environment file loading precedence and updates all relevant parts of the codebase. The new unit tests are comprehensive and cover the new functionality well. The code is clean and well-structured. I have no suggestions for improvement.