51 lines
2.3 KiB
Markdown
51 lines
2.3 KiB
Markdown
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# 2. Language-agnostic method extraction via `child_by_field_name("body")`
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**Date:** 2026-07-03
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**Status:** Accepted
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## Context
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To analyze method-level behavioral conventions, we must extract the body of each function/method from the AST. The standard tree-sitter approach is `node.child_by_field_name("body")`, but this named field is not universal across all language grammars.
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We need one code path that works for all 10 supported languages without per-language branches.
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## Decision
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Use `node.child_by_field_name("body")` as the primary extraction method. When it returns `None`, fall back to scanning the node's children for any child with a type containing `body`, `block`, or `compound_statement`.
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Parent nodes are further filtered to only include nodes whose type contains `function` or `method` — avoiding class bodies, loop bodies, and conditional blocks.
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This logic lives in `_find_method_bodies()` in `code.py`:
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```python
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def walk(node):
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body = node.child_by_field_name("body")
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if not body:
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for child in node.children:
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ctype = child.type.lower()
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if "body" in ctype or "block" in ctype or ctype == "compound_statement":
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body = child; break
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if body:
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ptype = node.type.lower()
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if "function" in ptype or "method" in ptype:
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bodies.append(body)
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for child in node.children: walk(child)
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```
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## Consequences
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**Positive:**
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- Works for 9/10 grammars via `child_by_field_name("body")` alone (Python, Go, Rust, JS, TS, Ruby, Java, C, C++).
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- Kotlin fallback works because the fwcd Kotlin grammar uses `function_body` as a child node type.
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- Zero per-language case analysis — just pattern matching on type strings.
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**Negative:**
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- Fallback relies on string matching (`"body" in ctype`) which could produce false positives if future grammar versions introduce new body-like types.
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- C/C++ `function_definition` uses `declarator` field for the function name, not `name` — affects name extraction but not body extraction.
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## Alternatives Considered
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- **Grammar-specific field names**: Map each language to its body field name. Rejected because it creates a maintenance burden and violates the zero-adapters constraint.
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- **Top-down sibling traversal**: Walk from node start to next sibling to find the body. Fragile across grammars with different compound statement structures.
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