mermaid/updated-mission.md

🚀 NOVEL APPROACH: Lexer-First Validation Strategy

Revolutionary Two-Phase Methodology

Phase 1: Lexer Validation (CURRENT FOCUS) 🎯

Objective: Ensure the Chevrotain lexer produces identical tokenization results to the JISON lexer for ALL existing test cases.

Why This Novel Approach:

• ❌ Previous attempts failed because lexer issues were masked by parser problems
• 🔍 Tokenization is the foundation - if it's wrong, everything else fails
• 📊 Systematic validation ensures no edge cases are missed
• ✅ Clear success criteria: all existing test cases must tokenize identically

Phase 1 Strategy:

1. Create comprehensive lexer comparison tests that validate Chevrotain vs JISON tokenization
2. Extract all test cases from existing JISON parser tests (flow.spec.js, flow-arrows.spec.js, etc.)
3. Build lexer validation framework that compares token-by-token output
4. Fix lexer discrepancies until 100% compatibility is achieved
5. Only then proceed to Phase 2

Phase 2: Parser Implementation (FUTURE) 🔮

Objective: Implement parser rules and AST visitors once lexer is proven correct.

Phase 2 Strategy:

1. Build on validated lexer foundation
2. Implement parser rules with confidence that tokenization is correct
3. Add AST visitor methods for node data processing
4. Test incrementally with known-good tokenization

Current Implementation Status

• ✅ Basic lexer tokens implemented: ShapeDataStart, ShapeDataContent, ShapeDataEnd
• ✅ Basic lexer modes implemented: shapeData_mode, shapeDataString_mode
• ❌ BLOCKED: Need to validate lexer against ALL existing test cases first
• ❌ BLOCKED: Parser implementation on hold until Phase 1 complete

Phase 1 Deliverables 📋

1. Lexer comparison test suite that validates Chevrotain vs JISON for all existing flowchart syntax
2. 100% lexer compatibility with existing JISON implementation
3. Comprehensive test coverage for edge cases and special characters
4. Documentation of any lexer behavior differences and their resolutions

Key Files for Phase 1 📁

• packages/mermaid/src/diagrams/flowchart/parser/flowLexer.ts - Chevrotain lexer
• packages/mermaid/src/diagrams/flowchart/parser/flow.jison - Original JISON lexer
• packages/mermaid/src/diagrams/flowchart/parser/flow*.spec.js - Existing test suites
• NEW: Lexer validation test suite (to be created)

Previous Achievements (Context) 📈

• ✅ Style parsing (100% complete) - All style, class, and linkStyle functionality working
• ✅ Arrow parsing (100% complete) - All arrow types and patterns working
• ✅ Subgraph parsing (95.5% complete) - Multi-word titles, number-prefixed IDs, nested subgraphs
• ✅ Direction statements - All direction parsing working
• ✅ Test file conversion - All 15 test files converted to Chevrotain format
• ✅ Overall Success Rate: 84.2% (550 passed / 101 failed / 2 skipped across all Chevrotain tests)

Why This Approach Will Succeed 🎯

1. Foundation-First: Fix the lexer before building on top of it
2. Systematic Validation: Every test case must pass lexer validation
3. Clear Success Metrics: 100% lexer compatibility before moving to Phase 2
4. Proven Track Record: Previous achievements show systematic approach works
5. Novel Strategy: No one has tried comprehensive lexer validation first

Immediate Next Steps ⚡

1. Create lexer validation test framework
2. Extract all test cases from existing JISON tests
3. Run comprehensive lexer comparison
4. Fix lexer discrepancies systematically
5. Achieve 100% lexer compatibility
6. Then and only then proceed to parser implementation

This Novel Approach is Revolutionary Because 🌟

Previous Approaches Failed Because:

• ❌ Tried to fix parser and lexer simultaneously
• ❌ Lexer issues were hidden by parser failures
• ❌ No systematic validation of tokenization
• ❌ Built complex features on unstable foundation

This Approach Will Succeed Because:

• ✅ Foundation-first methodology - Fix lexer completely before parser
• ✅ Systematic validation - Every test case must pass lexer validation
• ✅ Clear success metrics - 100% lexer compatibility required
• ✅ Proven track record - Previous systematic approaches achieved 84.2% success
• ✅ Novel strategy - No one has tried comprehensive lexer validation first

Success Criteria for Phase 1 ✅

• 100% lexer compatibility with JISON for all existing test cases
• Comprehensive test suite that validates every tokenization scenario
• Zero lexer discrepancies between Chevrotain and JISON
• Documentation of lexer behavior and edge cases
• Foundation ready for Phase 2 parser implementation

Expected Timeline ⏰

• Phase 1: 1-2 weeks of focused lexer validation
• Phase 2: 2-3 weeks of parser implementation (with solid foundation)
• Total: 3-5 weeks to complete node data syntax implementation

Why This Will Work 💪

1. Systematic approach has already achieved 84.2% success rate
2. Lexer-first strategy eliminates the most common source of failures
3. Clear validation criteria prevent moving forward with broken foundation
4. Novel methodology addresses root cause of previous failures
5. Proven track record of systematic development success

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🎯 CURRENT MISSION: Create comprehensive lexer validation test suite and achieve 100% Chevrotain-JISON lexer compatibility before any parser work.