[cfg] Python buildFunctionCfg skipped a function in ${filePa

Error message

[cfg] Python buildFunctionCfg skipped a function in ${filePath}: ${String(err)}

What it means

During indexing GitNexus builds a per-function control-flow graph (CFG) with a Python tree-sitter visitor (PY_FUNCTION_TYPES). buildFunctionCfg wraps the body walk (visitSeq over the body's namedChildren minus comments) in a catch-all: any throw from an unexpected AST shape is logged with console.warn and only that function's CFG is skipped (returns undefined), protecting the file's language group ('R4' isolation).

Source

Thrown at gitnexus/src/core/ingestion/cfg/visitors/python.ts:760

      builder.edge(builder.entryIndex, blk, 'seq');
      builder.edge(blk, builder.exitIndex, 'return');
      return builder.finish(harvest.bindingTable());
    }

    const walk = new PythonCfgWalk(builder, harvest);
    const res = walk.visitSeq(body.namedChildren.filter((c) => c.type !== 'comment'));
    if (!res) {
      builder.edge(builder.entryIndex, builder.exitIndex, 'seq'); // empty body
      return builder.finish(harvest.bindingTable());
    }
    builder.edge(builder.entryIndex, res.entry, 'seq');
    builder.connect(res.exits, builder.exitIndex, 'seq'); // normal fall-off → EXIT
    return builder.finish(harvest.bindingTable());
  } catch (err) {
    // Never throw out of buildFunctionCfg — a malformed AST shape must skip only
    // this one function's CFG, never drop the whole file's language group (R4).
    // eslint-disable-next-line no-console
    console.warn(`[cfg] Python buildFunctionCfg skipped a function in ${filePath}: ${String(err)}`);
    return undefined;
  }
}

/** Whether a node is a Python function this visitor builds a CFG for. */
function isFunction(node: SyntaxNode): boolean {
  return PY_FUNCTION_TYPES.has(node.type);
}

/** The Python CFG visitor. */
export function createPythonCfgVisitor(): CfgVisitor<SyntaxNode> {
  return { buildFunctionCfg, isFunction };
}

export { PY_FUNCTION_TYPES };

View on GitHub (pinned to aac7515d2a)

Solutions

Read the ${String(err)} portion of the warning for the underlying exception
Index only the affected file, then inspect the tree around the failing def/lambda
Reinstall dependencies to resync the grammar or patch the Python visitor for the node type
Re-run analyze --index-only to rebuild the CFG layer
Accept the skip — the rest of the file indexes normally

Defensive patterns

Strategy: fallback

Validate before calling

// prescreen: tree-sitter marks invalid Python with ERROR/MISSING nodes
if (tree.rootNode.hasError) fixSourceOrExclude(file);

Try / catch

const cfg = visitor.buildFunctionCfg(fn, ctx);
if (cfg === undefined) continue; // warned skip: def/lambda without CFG

Prevention

Do not index files mid-edit with syntax errors
Resync the Python grammar on upgrades
Reproduce match/decorator/async shapes on a single file when reporting
Treat absent CFG as UNKNOWN risk in impact decisions

When it happens

Trigger: A Python construct the walker does not model: structural pattern matching (match/case), decorated async bodies, walrus-heavy expressions, or ERROR/MISSING nodes when tree-sitter parses invalid Python, causing a throw during visitSeq.

Common situations: Grammar version drift between the Python grammar and the visitor; indexing files mid-edit with syntax errors; notebooks or generated Python with unusual indentation node shapes; newer CPython syntax the visitor predates.

Related errors

AI-assisted analysis of abhigyanpatwari/GitNexus@aac7515d2a (2026-08-20). Data as JSON: /api/errors/9bb8df8ba1fffe4a. Report an issue: GitHub.