# 2. Language-agnostic method extraction via `child_by_field_name("body")`

**Date:** 2026-07-03

**Status:** Accepted

## Context

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.

We need one code path that works for all 10 supported languages without per-language branches.

## Decision

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`.

Parent nodes are further filtered to only include nodes whose type contains `function` or `method` — avoiding class bodies, loop bodies, and conditional blocks.

This logic lives in `_find_method_bodies()` in `code.py`:

```python
def walk(node):
    body = node.child_by_field_name("body")
    if not body:
        for child in node.children:
            ctype = child.type.lower()
            if "body" in ctype or "block" in ctype or ctype == "compound_statement":
                body = child; break
    if body:
        ptype = node.type.lower()
        if "function" in ptype or "method" in ptype:
            bodies.append(body)
    for child in node.children: walk(child)
```

## Consequences

**Positive:**
- Works for 9/10 grammars via `child_by_field_name("body")` alone (Python, Go, Rust, JS, TS, Ruby, Java, C, C++).
- Kotlin fallback works because the fwcd Kotlin grammar uses `function_body` as a child node type.
- Zero per-language case analysis — just pattern matching on type strings.

**Negative:**
- Fallback relies on string matching (`"body" in ctype`) which could produce false positives if future grammar versions introduce new body-like types.
- C/C++ `function_definition` uses `declarator` field for the function name, not `name` — affects name extraction but not body extraction.

## Alternatives Considered

- **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.
- **Top-down sibling traversal**: Walk from node start to next sibling to find the body. Fragile across grammars with different compound statement structures.
