Aggregate validation errors across workflow compilation passes

[Copilot]

Validation functions were returning on first error, requiring users to fix issues sequentially. This implements multi-error aggregation using errors.Join() to surface all validation issues in a single compilation pass.

Changes

repository_features_validation.go

• Aggregate discussions and issues feature checks with ErrorCollector
• Surface all repository capability errors together

dispatch_workflow_validation.go

• Collect errors across all workflows in dispatch list
• Report self-reference, missing files, and trigger issues in one pass

template_validation.go

• Use errors.Join() for import directives in template regions
• Aggregate all violations across template blocks

bundler_runtime_validation.go

• No code changes (already uses fail-fast for recursive dependency resolution)
• Added comment documenting the fail-fast rationale

Example Output

Before:

Error: dispatch-workflow: self-reference not allowed (workflow 'dispatcher' cannot dispatch itself)

After:

Found 3 dispatch-workflow errors:
  • dispatch-workflow: self-reference not allowed (workflow 'dispatcher' cannot dispatch itself)
  • dispatch-workflow: workflow 'ci' does not support workflow_dispatch trigger
  • dispatch-workflow: workflow 'nonexistent' not found in .github/workflows

All implementations respect the existing --fail-fast flag for users preferring immediate error feedback.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Code Quality] Implement error aggregation for validation using errors.Join()</issue_title>
<issue_description>## Description

Implement multi-error aggregation using errors.Join() (Go 1.20+) in validation files to show users all validation errors at once instead of failing on first error. This dramatically improves feedback loops and developer experience.

Problem

Zero uses of errors.Join() despite Go 1.20+ multi-error support. Validation files return first error and hide subsequent issues. Users must fix errors one-by-one instead of seeing full context, leading to slow feedback loops and frustrated developers.

Suggested Changes

Priority Files to Update

1. pkg/workflow/bundler_runtime_validation.go
2. pkg/workflow/repository_features_validation.go
3. pkg/workflow/dispatch_workflow_validation.go
4. pkg/workflow/template_validation.go
5. pkg/workflow/strict_mode_validation.go

Implementation Pattern

func ValidateConfiguration(config *Config) error {
    var errs []error
    
    // Collect all validation errors
    if err := validateField1(config); err != nil {
        errs = append(errs, err)
    }
    
    if err := validateField2(config); err != nil {
        errs = append(errs, err)
    }
    
    if err := validateField3(config); err != nil {
        errs = append(errs, err)
    }
    
    // Return aggregated errors
    if len(errs) > 0 {
        return errors.Join(errs...)
    }
    
    return nil
}

Success Criteria

• Update validation files to collect all errors before returning
• Use errors.Join() to aggregate multiple validation errors
• Maintain error ordering (most critical first)
• Update tests to verify multi-error behavior
• Ensure console formatting works with aggregated errors

Testing Example

func TestValidation_MultipleErrors(t *testing.T) {
    config := &Config{
        InvalidField1: "bad",
        InvalidField2: "worse",
    }
    
    err := ValidateConfiguration(config)
    
    require.Error(t, err)
    assert.Contains(t, err.Error(), "invalid field1")
    assert.Contains(t, err.Error(), "invalid field2")
}

Impact

Users see ALL validation issues in one run instead of fixing errors one-by-one.

Source

Extracted from Error Experience Engineering Discussion github/gh-aw#12265

Priority

High - Dramatically improves developer feedback loops

Estimated Effort

Large (1-2 weeks)

AI generated by Discussion Task Miner - Code Quality Improvement Agent

• expires on Feb 18, 2026, 9:08 PM UTC

Comments on the Issue (you are @copilot in this section)

• Fixes [Code Quality] Implement error aggregation for validation using errors.Join() #13791

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[Copilot]

Pull request overview

This PR implements multi-error aggregation for workflow validation functions to improve developer feedback loops. Instead of stopping at the first validation error, the compiler now collects all issues and presents them together using Go's errors.Join() and a new ErrorCollector utility.

Changes:

• Added error aggregation to dispatch workflow validation, repository features validation, and template validation
• Implemented ErrorCollector utility to handle fail-fast mode and formatted error output
• Added comprehensive tests for multi-error scenarios and fail-fast behavior

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
pkg/workflow/template_validation.go	Aggregates import directive violations across template blocks
pkg/workflow/template_include_validation_test.go	Tests multi-error aggregation and single-error behavior for template validation
pkg/workflow/repository_features_validation.go	Collects repository capability errors (discussions/issues) using ErrorCollector
pkg/workflow/dispatch_workflow_validation.go	Aggregates errors across workflows in dispatch list (self-references, missing files, trigger issues)
pkg/workflow/dispatch_workflow_test.go	Tests multi-error and fail-fast modes for dispatch workflow validation
pkg/workflow/bundler_runtime_validation.go	Documentation update explaining fail-fast rationale for recursive dependency resolution

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[Copilot]

Corrected spelling of 'to' to 'checking'; the comment should read 'Continue checking other features even if this check fails' to match the pattern established in line 134.

Suggested change

	// Continue to return aggregated errors even if this check fails
	// Continue checking other features even if this check fails

[Copilot]

Multiple identical comments 'Skip further validation for this workflow' repeated throughout the function create noise. Consider reducing these comments or making them more specific to each validation step (e.g., 'Skip after self-reference check', 'Skip after file read error').

[Copilot]

Multiple identical comments 'Skip further validation for this workflow' repeated throughout the function create noise. Consider reducing these comments or making them more specific to each validation step (e.g., 'Skip after self-reference check', 'Skip after file read error').

[Copilot]

Multiple identical comments 'Skip further validation for this workflow' repeated throughout the function create noise. Consider reducing these comments or making them more specific to each validation step (e.g., 'Skip after self-reference check', 'Skip after file read error').

[Copilot]

Multiple identical comments 'Skip further validation for this workflow' repeated throughout the function create noise. Consider reducing these comments or making them more specific to each validation step (e.g., 'Skip after self-reference check', 'Skip after file read error').

[Copilot]

Multiple identical comments 'Skip further validation for this workflow' repeated throughout the function create noise. Consider reducing these comments or making them more specific to each validation step (e.g., 'Skip after self-reference check', 'Skip after file read error').

[Copilot]

Multiple identical comments 'Skip further validation for this workflow' repeated throughout the function create noise. Consider reducing these comments or making them more specific to each validation step (e.g., 'Skip after self-reference check', 'Skip after file read error').

[Copilot]

Multiple identical comments 'Skip further validation for this workflow' repeated throughout the function create noise. Consider reducing these comments or making them more specific to each validation step (e.g., 'Skip after self-reference check', 'Skip after file read error').

[Copilot]

Multiple identical comments 'Skip further validation for this workflow' repeated throughout the function create noise. Consider reducing these comments or making them more specific to each validation step (e.g., 'Skip after self-reference check', 'Skip after file read error').

[Copilot]

Multiple identical comments 'Skip further validation for this workflow' repeated throughout the function create noise. Consider reducing these comments or making them more specific to each validation step (e.g., 'Skip after self-reference check', 'Skip after file read error').