The Issue

• Project traefik config could be preprocessed into a single unique file #8047

In DDEV v1.25.0, the project traefik config has been standardized to only accept a single file in the project .ddev/traefik/config/<projectname>.yaml. If users want to customize it, they must remove the #ddev-generated line and take full responsibility for maintaining the entire file. This makes it difficult to add custom configuration without losing the benefits of DDEV's automatic config generation.

How This PR Solves The Issue

This PR implements automatic merging of multiple traefik configuration files within a project:

1. Core Implementation: Modified PushGlobalTraefikConfig() in pkg/ddevapp/traefik.go to:

   • Glob all *.yaml files in the project's .ddev/traefik/config/ directory
   • Merge them using the existing util.MergeYamlFiles() function with <projectname>.yaml as the base
   • Output the merged result as <projectname>_merged.yaml in the global traefik config directory (~/.ddev/traefik/config/)
   • Maintain backward compatibility - projects with only one config file work without changes

2. How It Works:

   • DDEV generates the base <projectname>.yaml file as usual (with #ddev-generated)
   • Users can add custom configuration in additional *.yaml files (e.g., custom-middleware.yaml, extra-routes.yaml)
   • On ddev start, all files are merged together (with mergo's override strategy - later files override earlier ones alphabetically)
   • The merged result is copied to ~/.ddev/traefik/config/<projectname>_merged.yaml and picked up by Traefik

3. Benefits:

   • Users can add custom configuration without removing #ddev-generated
   • DDEV continues to maintain the base configuration
   • Custom additions are preserved through DDEV updates
   • Configuration is modular and easier to manage

Manual Testing Instructions

1. Create or use an existing DDEV project
2. Start the project with ddev start
3. Create a custom traefik config file in .ddev/traefik/config/, for example:

   cat > .ddev/traefik/config/custom-middleware.yaml << 'YAML'
   # Custom middleware configuration
   http:
     middlewares:
       my-custom-headers:
         headers:
           customRequestHeaders:
             X-Custom-Header: "my-value"
   YAML

4. Restart the project: ddev restart
5. Verify the merged config exists: ls ~/.ddev/traefik/config/<projectname>_merged.yaml
6. Check the merged config contains both generated and custom content:

   cat ~/.ddev/traefik/config/<projectname>_merged.yaml

7. Verify the project still works correctly by accessing it in a browser

To test HTTP→HTTPS redirect (as in the integration test):

1. Add a redirect config:

   cat > .ddev/traefik/config/redirect-https.yaml << 'YAML'
   http:
     routers:
       <projectname>-web-80-http:
         middlewares:
           - "<projectname>-redirectHttps"
   YAML

2. Restart: ddev restart
3. Test HTTP access redirects to HTTPS: curl -I http://<projectname>.ddev.site
4. Should receive a 301/308 redirect to HTTPS

Automated Testing Overview

Unit Tests:

• Added test case to TestMergeYamlFiles in pkg/util/yaml_test.go to verify YAML merging logic
• Test data in pkg/util/testdata/TestMergeYamlFiles/traefikConfigMerge/ with multiple config files

Integration Test:

• Added TestMergeTraefikProjectConfig in pkg/ddevapp/traefik_test.go that:
  • Creates a project and generates base traefik config
  • Adds an extra yaml file that enables the redirectHttps middleware
  • Verifies the merged config exists in ~/.ddev/traefik/config/<projectname>_merged.yaml
  • Confirms the merged config contains the middleware reference
  • Tests that the project is accessible
  • Tests that HTTP requests are actually redirected to HTTPS (301/308 status)

Test Reliability:

• Test follows patterns from working tests in the codebase
• Includes accessibility checks before testing specific behaviors
• Uses require assertions for critical validations

Release/Deployment Notes

Backward Compatibility:

• Fully backward compatible - existing projects continue to work without changes
• Projects with only one config file (<projectname>.yaml) are simply copied as <projectname>_merged.yaml
• Projects that have removed #ddev-generated continue to work as before

Breaking Changes:

• None. The feature is additive and opt-in.

Documentation:

• Updated docs/content/users/extend/traefik-router.md with:
  • Explanation of the merge functionality
  • Example of adding custom middleware
  • Clarification of when to use merge vs. taking over configuration

Migration Notes:

• No migration needed for existing projects
• Old <projectname>.yaml files from the volume are automatically cleaned up
• The new <projectname>_merged.yaml naming is used consistently for all projects

• Fixes Project traefik config could be preprocessed into a single unique file #8047

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