Gabriel Kaszewski
35f27d00b0
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Hex arch + DDD, tree-sitter parsing, Mermaid/ASCII output. Supports Rust + Python. 92 tests. CI, diff, --check for staleness detection.
32 lines
1.9 KiB
Markdown
32 lines
1.9 KiB
Markdown
# 0002 — Tree-sitter for Source Code Parsing
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**Status:** Accepted
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**Date:** 2026-06-16
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## Context
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Archlens needs to extract type-level information (classes, structs, traits, interfaces, enums, fields, inheritance) from Rust, C#, and Python source code. The tool must be language-agnostic in design, fast enough for CI, and memory-efficient for large codebases.
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## Decision
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Use tree-sitter as the primary parsing backend. One `tree-sitter` adapter crate with internal modules per language. Each language module defines tree-sitter S-expression queries to extract CodeElements and Relationships.
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**Tradeoff accepted:** Tree-sitter provides syntactic analysis only — no cross-file type resolution, no generics resolution, no resolved imports. This is sufficient for architecture diagrams where we care about structural relationships visible in the source text.
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Semantic resolution is a future concern, handled by a separate adapter (e.g., `roslyn-adapter` for C#) implementing the same `SourceAnalyzer` port.
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## Alternatives Considered
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- **Custom parsers/lexers per language:** Full control but enormous implementation and maintenance effort. Rejected.
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- **LSP servers:** Rich semantic info but heavy to run, hard to orchestrate in CI, each language needs its own server process. Rejected for CI use case.
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- **Native AST APIs (Roslyn, rustc_ast, Python ast):** Very accurate but each is a completely different API and ecosystem. Can't run Roslyn from Rust easily. Rejected as primary approach — viable as future specialized adapters.
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- **Regex/heuristic:** Breaks on edge cases. Not serious for a real tool.
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## Consequences
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- Single unified parsing approach across all languages
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- Adding a new language = writing tree-sitter queries (hours, not weeks)
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- No semantic type resolution — `use Foo` doesn't tell us which `Foo` across modules
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- Memory-efficient: parse trees are per-file and dropped after extraction
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- Fast: tree-sitter is incremental and optimized for performance
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