feat(testing): support browser executable path detection via environm…

[christian-bromann]

What is the current behavior?

GitHub Issue Number: #6213

The PUPPETEER_EXECUTABLE_PATH environment variable is not being respected when running Stencil tests with Puppeteer. Users who set this environment variable to specify a custom browser executable (e.g., in Docker environments where Chromium is installed separately) encounter errors because Stencil is not using the specified path.

The current implementation only checks config.testing.browserExecutablePath but ignores common environment variables that users expect to work with Puppeteer.

What is the new behavior?

This PR implements a robust fallback chain for browser executable path detection:

1. Environment Variables Support: Automatically detects browser executables from:

   • PUPPETEER_EXECUTABLE_PATH - Standard Puppeteer environment variable
   • CHROME_PATH - Common Chrome/Chromium path variable
   • Falls back to puppeteer.puppeteerExecutablePath() if neither is set

2. Improved Documentation: Added comprehensive JSDoc documentation for the browserExecutablePath property explaining the new default behavior and fallback chain.

3. Simplified Logic: Removed conditional logic in favor of a unified fallback resolution approach that always provides a value.

This change ensures that users can specify browser executables through environment variables without requiring explicit configuration, which is especially important for CI/CD environments and Docker deployments.

Documentation

The JSDoc documentation for TestingConfig.browserExecutablePath has been updated to reflect the new default behavior and fallback chain.

Does this introduce a breaking change?

• Yes
• No

This change is backward compatible. The browserExecutablePath configuration option still works as before, but now users have additional options through environment variables when this config is not explicitly set.

Testing

• Verified that existing browserExecutablePath configuration still works
• Tested environment variable fallback chain:
  • PUPPETEER_EXECUTABLE_PATH takes precedence
  • CHROME_PATH is used when PUPPETEER_EXECUTABLE_PATH is not set
  • Default Puppeteer executable path is used when neither environment variable is set
• Confirmed the fix resolves the issue described in bug: PUPPETEER_EXECUTABLE_PATH broken since 4.24.0 #6213

Other information

This addresses the regression introduced in recent versions where PUPPETEER_EXECUTABLE_PATH stopped working. The fix ensures that Docker users and CI/CD environments can continue to use this standard environment variable to specify custom browser executables without additional configuration.

The implementation follows Puppeteer's own environment variable conventions, making it more intuitive for users already familiar with Puppeteer's behavior.

[ReneWerner87]

testing of the fix
#6213 (comment)