[EPIC] F# Code Generation Backend

[DamianReeves]

Description

Implement a complete F# code generation backend for morphir-dotnet that transforms Morphir IR (JSON) into idiomatic, type-safe F# code using Fabulous.AST and Fantomas.

Vision

Enable developers to generate production-ready F# code from Morphir IR, eliminating manual translation and maintaining type safety throughout the business logic transformation.

Goals

• ✅ Generate idiomatic F# code from Morphir IR v3
• ✅ Support all Morphir type and value constructs
• ✅ Map Morphir SDK types to F# built-in types
• ✅ Integrate with morphir gen fsharp CLI command
• ✅ Auto-format output using Fantomas
• ✅ Support JSON codecs and lens generation (optional)
• ✅ Achieve ≥80% test coverage
• ✅ AOT-compatible generated code

Success Metrics

• All Morphir IR v3 constructs generate valid F# code
• Generated code compiles without errors
• Performance: < 5s for 1000 types
• Test coverage ≥ 80%
• At least 3 example projects using the backend

Related Documentation

• PRD: F# Backend
• Design README
• Maturity Milestones
• GitHub Issues Template

Child Issues

• Phase 0: Morphir.SDK F# Library Implementation #364 Phase 0: Morphir.SDK F# Library Implementation
• Phase 1: Foundation - Project Setup and Fabulous.AST Exploration #365 Phase 1: Foundation - Project Setup and Fabulous.AST Exploration
• Phase 2: Type Mapping - Morphir IR Types → F# Types #366 Phase 2: Type Mapping - Morphir IR Types → F# Types
• Phase 3: Value Mapping - Morphir IR Values → F# Functions #367 Phase 3: Value Mapping - Morphir IR Values → F# Functions
• Phase 4: CLI Integration - morphir gen fsharp Command #368 Phase 4: CLI Integration - morphir gen fsharp Command
• Phase 5: SDK Translation - Morphir SDK → F# Standard Library #369 Phase 5: SDK Translation - Morphir SDK → F# Standard Library
• Phase 6: Advanced Features - JSON Codecs and Lenses #370 Phase 6: Advanced Features - JSON Codecs and Lenses
• Phase 7: Testing and Documentation #372 Phase 7: Testing and Documentation
• Phase 8: Release Preparation #371 Phase 8: Release Preparation

Dependencies

• Fabulous.AST v1.9.0+ (already in Directory.Packages.props)
• Fantomas.Core v7.0.5+ (already in Directory.Packages.props)
• Morphir.IR.Pipeline (transformation infrastructure)
• Morphir.SDK (F# runtime library - Phase 0: Morphir.SDK F# Library Implementation #364)

Timeline

Total Duration: 13 weeks (1 week Phase 0 + 12 weeks implementation)
Target Completion: Q2 2025