[file-diet] File Diet: refactor pkg/workflow/workflow_builder.go (1084 lines)

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Overview

The file pkg/workflow/workflow_builder.go has grown to 1084 lines, exceeding the healthy threshold of 800 lines. This task involves refactoring it into smaller, focused files with improved test coverage.

Current State

• File: pkg/workflow/workflow_builder.go
• Size: 1084 lines
• Test Coverage: No dedicated workflow_builder_test.go file exists. Some of its 32 functions are exercised indirectly by other test files (e.g. github_app_owner_derivation_test.go and others), but there is no focused unit-test file for this module.
• Complexity: Mixed responsibilities — the file combines initial workflow-data construction, YAML section extraction, model cost/policy overlay merging, concurrency/dispatch extraction, and pre/post step merging in a single file.

Full File Analysis

Detailed Breakdown

32 top-level functions identified, grouped by responsibility:

1. Workflow data initialization

• buildInitialWorkflowData (line 19) — large orchestrator method on *Compiler

2. Config extraction helpers

• extractEnclavesConfig (220)
• extractLSPConfig (236)
• extractFrontmatterSkills (264)
• extractFrontmatterPlugins (283)
• mergeFrontmatterPlugins (301)
• extractFrontmatterSkillReferences (306)

3. Model cost/policy overlay merging (largest cohesive cluster, lines ~322-620)

• extractMainModelCostsOverlay (322)
• mergeModelCostOverlays (353)
• mergeModelCostOverlayPair (374)
• extractMainModelPolicyOverlay (426)
• toFloat64 (452)
• resolveDefaultAiCreditsPricing (477)
• extractDefaultAiCreditsPricingFromModels (486)
• extractDefaultAiCreditsPricingFromModelsMap (494)
• extractDefaultAiCreditsPricingFromObject (509)
• mergeModelPolicyOverlays (536)
• filterAllowedModelConflictsWithSet (575)
• modelConflictsWithDisallowedPolicy (589)
• modelPolicyPatternMatches (606)

4. Import/env merging utilities

• resolveInlinedImports (623)
• mergeExcludedEnvVarNames (630)

5. YAML section / concurrency / dispatch extraction

• extractYAMLSections (656) — method on *Compiler
• extractConcurrencyJobDiscriminator (691)
• extractConcurrencySection (714) — method on *Compiler
• extractDispatchItemNumber (754)

6. Step merging (pre/post/pre-agent) (largest LOC cluster, lines 784-1069)

• processAndMergeSteps (784)
• processAndMergePreSteps (883)
• processAndMergePreAgentSteps (945)
• processAndMergePostSteps (1004)
• frontmatterHasTrigger (1069)

This gives 5 clear functional domains that map naturally onto separate files, following the repository's existing "domain file" pattern used elsewhere in pkg/workflow/.

Refactoring Strategy

Proposed File Splits

Based on the semantic grouping above, split the file into the following modules:

1. workflow_builder_model_overlays.go

   • Functions: extractMainModelCostsOverlay, mergeModelCostOverlays, mergeModelCostOverlayPair, extractMainModelPolicyOverlay, toFloat64, resolveDefaultAiCreditsPricing, extractDefaultAiCreditsPricingFromModels, extractDefaultAiCreditsPricingFromModelsMap, extractDefaultAiCreditsPricingFromObject, mergeModelPolicyOverlays, filterAllowedModelConflictsWithSet, modelConflictsWithDisallowedPolicy, modelPolicyPatternMatches
   • Responsibility: Model cost and policy overlay extraction/merging (AI credits pricing, allowed/disallowed model policy resolution)
   • Estimated LOC: ~300

2. workflow_builder_steps.go

   • Functions: processAndMergeSteps, processAndMergePreSteps, processAndMergePreAgentSteps, processAndMergePostSteps, frontmatterHasTrigger
   • Responsibility: Merging pre/pre-agent/post step lists from frontmatter and imports
   • Estimated LOC: ~290

3. workflow_builder_frontmatter_extract.go

   • Functions: extractEnclavesConfig, extractLSPConfig, extractFrontmatterSkills, extractFrontmatterPlugins, mergeFrontmatterPlugins, extractFrontmatterSkillReferences, extractYAMLSections, extractConcurrencyJobDiscriminator, extractConcurrencySection, extractDispatchItemNumber, resolveInlinedImports, mergeExcludedEnvVarNames
   • Responsibility: Small, focused frontmatter field extraction helpers (enclaves, LSP, skills, plugins, concurrency, dispatch, imports)
   • Estimated LOC: ~330

4. workflow_builder.go (remaining)

   • Functions: buildInitialWorkflowData (core orchestrator)
   • Responsibility: Top-level workflow-data construction, calling into the extracted helper files
   • Estimated LOC: ~210

Shared Utilities

No additional cross-cutting utility file is required; toFloat64 stays with the model overlay group since it is only used there.

Interface Abstractions

Not needed — these are stateless helper functions and methods on *Compiler; no new interfaces are warranted.

Test Coverage Plan

Add comprehensive tests for each new file:

1. workflow_builder_model_overlays_test.go

   • Test cases: cost overlay merge precedence (main overrides imports), policy overlay allow/disallow conflict resolution, AI credits pricing extraction from various frontmatter shapes, toFloat64 edge cases (int, float, string, invalid)
   • Target coverage: >80%

2. workflow_builder_steps_test.go

   • Test cases: merging pre/post/pre-agent steps from multiple imports, ordering guarantees, frontmatterHasTrigger detection for string/array/map trigger shapes
   • Target coverage: >80%

3. workflow_builder_frontmatter_extract_test.go

   • Test cases: enclaves config extraction defaults, LSP server config parsing, skill/plugin extraction and merging, concurrency discriminator/section extraction, dispatch item-number flag detection, inlined-imports resolution, excluded env var merging
   • Target coverage: >80%

4. workflow_builder_test.go (new, currently missing)

   • Test cases: buildInitialWorkflowData end-to-end construction with representative frontmatter fixtures
   • Target coverage: >80%

Implementation Guidelines

1. Preserve Behavior: Ensure all existing functionality works identically
2. Maintain Exports: Keep public API unchanged (exported functions/types)
3. Add Tests First: Write tests for each new file before refactoring
4. Incremental Changes: Split one module at a time
5. Run Tests Frequently: Verify make test-unit passes after each split
6. Update Imports: Ensure all import paths are correct
7. Document Changes: Add comments explaining module boundaries

Acceptance Criteria

• Original file is split into 4 focused files
• Each new file is under 500 lines
• All tests pass (make test-unit)
• Test coverage is ≥80% for new files
• No breaking changes to public API
• Code passes linting (make lint)
• Build succeeds (make build)

Additional Context

• Repository Guidelines: Follow patterns in .github/agents/developer.instructions.agent.md
• Code Organization: Prefer many small files grouped by functionality
• Testing: Match existing test patterns in pkg/workflow/*_test.go

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Priority: Medium
Effort: Medium — 32 functions across 5 domains, no existing dedicated test file to preserve/migrate
Expected Impact: Improved maintainability, easier testing, reduced complexity

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• expires on Aug 23, 2026, 5:01 AM UTC-08:00

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