fix(dataflow): Dart local variable declarations and calls never tracked

src/ast-analysis/rules/b2.ts

@@ -570,6 +570,69 @@ function extractDartParamName(node: TreeSitterNode): string[] | null {
   return null;
 }
 
+/** Walk backward past any unnamed (anonymous token) siblings to the nearest named one. */
+function prevNamedSibling(node: TreeSitterNode): TreeSitterNode | null {
+  let p = node.previousSibling;
+  while (p && !p.isNamed) p = p.previousSibling;
+  return p;
+}
+
+/**
+ * Resolve a Dart call's callee name and argument-list node (issue #2357).
+ *
+ * tree-sitter-dart has no `call_expression` node type at all — confirmed via
+ * node-types.json — AND, contrary to this fix's first attempt, the grammar's
+ * own `postfix_expression` node (which node-types.json lists as the
+ * conceptual wrapper) never actually appears in a parsed tree either:
+ * tree-sitter elides/inlines it, so a call is a FLAT SEQUENCE OF SIBLINGS
+ * under whatever encloses it (`return_statement`, `expression_statement`,
+ * `initialized_variable_definition`, etc.) — confirmed empirically by
+ * dumping real parse trees for `return helper(x);`, `helper(x);`, and
+ * `obj.method(x);`. `helper(x)` is `[identifier "helper", selector "(x)"]`;
+ * `obj.method(x)` is `[identifier "obj", selector ".method", selector "(x)"]`
+ * — TWO sibling selectors, not one node containing both. `selector` itself
+ * IS a real, distinctly-dispatchable node (unlike postfix_expression), so
+ * `node` here is the CALL selector (the one wrapping `argument_part`) —
+ * `callNode: 'selector'` dispatches this function once per selector the
+ * generic walk visits; a non-call selector (bare `.prop` access, `[index]`)
+ * returns null via the argument_part check below. The callee is resolved by
+ * walking BACKWARD to this selector's preceding sibling: another selector
+ * (a `.property` access — the method-call case) or a bare `identifier` (the
+ * base — the bare-call case).
+ *
+ * Only resolves the OUTERMOST call in a chain (`a.b().c()` resolves `.c()`
+ * only) — there is no separate node for each intermediate call in Dart's
+ * flat sibling chain, matching this issue's own scope (a single call, not
+ * chained calls).
+ */
+function resolveDartCallParts(
+  node: TreeSitterNode,
+): { callee: string; argsNode: TreeSitterNode } | null {
+  const argumentPart = node.namedChildren.find((c) => c.type === 'argument_part');
+  if (!argumentPart) return null;
+  const argsNode = argumentPart.namedChildren.find((c) => c.type === 'arguments');
+  if (!argsNode) return null;
+
+  const prev = prevNamedSibling(node);
+  if (!prev) return null;
+
+  let calleeNode: TreeSitterNode | null = null;
+  if (prev.type === 'selector') {
+    // obj.method(x): the preceding selector wraps the property identifier.
+    const propWrapper = prev.namedChildren[0];
+    calleeNode =
+      propWrapper?.type === 'unconditional_assignable_selector'
+        ? (propWrapper.namedChildren[0] ?? null)
+        : null;
+  } else if (prev.type === 'identifier') {
+    // helper(x): the preceding identifier IS the callee.
+    calleeNode = prev;
+  }
+  if (calleeNode?.type !== 'identifier') return null;
+
+  return { callee: calleeNode.text, argsNode };
+}
+
 export const dataflowDart: DataflowRulesConfig = makeDataflowRules({
   functionNodes: new Set(['function_signature', 'method_signature']),
   // tree-sitter-dart puts a function's body in a SIBLING node, not a child
@@ -595,6 +658,14 @@ export const dataflowDart: DataflowRulesConfig = makeDataflowRules({
   getParamListNode: getDartParamListNode,
   extractParamName: extractDartParamName,
 
+  // local_variable_declaration's ONLY child is initialized_variable_definition,
+  // which has real `name`/`value` fields (confirmed via node-types.json) —
+  // this was left entirely unconfigured (issue #2357), so `var sum = ...;`
+  // never produced an assignment entry regardless of the sibling-body fix.
+  varDeclaratorNode: 'initialized_variable_definition',
+  varNameField: 'name',
+  varValueField: 'value',
+
   returnNode: 'return_statement',
   // Arrow/`=>`-style implicit return (issue #2356): tree-sitter-dart's
   // function_body node's ONLY child is either a `block` (`{ ... }`) or one
@@ -603,9 +674,27 @@ export const dataflowDart: DataflowRulesConfig = makeDataflowRules({
   // already matches Dart's own block type name.
   implicitReturnBodyNode: 'function_body',
 
-  callNode: 'call_expression',
-  // tree-sitter-dart does not have standard named fields for calls;
-  // the extractor uses `selector` nodes instead. Leave defaults.
+  // tree-sitter-dart has no call_expression node type at all, and its
+  // conceptual postfix_expression wrapper never actually materializes in a
+  // parsed tree either — a call is a flat sequence of siblings (see
+  // resolveDartCallParts's doc comment, issue #2357). `selector` is the one
+  // node in that sequence that's reliably, distinctly dispatchable — it
+  // wraps `argument_part` exactly when this specific selector is a call.
+  callNode: 'selector',
+  resolveCallParts: resolveDartCallParts,
+  // A call-sourced var declarator's `value` field resolves to the CALLEE's
+  // own base expression (an `identifier`), not the call itself — the call's
+  // argument-list selector is a SIBLING, found by walking forward through
+  // this same chain of selectors (findCallSelector, dataflow-visitor.ts).
+  // Without this, `var x = helper(y);` never registers an assignment entry
+  // even though the standalone call `helper(y)` is correctly tracked above.
+  callChainSiblingType: 'selector',
+  // `arguments`'s own children wrap each argument in an `argument` node
+  // (confirmed via node-types.json — same wrapper name PHP's config already
+  // unwraps), not a bare expression directly — without this, unwrapArg never
+  // finds the identifier inside and argFlows stays empty regardless of the
+  // callNode/resolveCallParts fix above.
+  argumentWrapperType: 'argument',
 });
 
 // ─── Groovy ───────────────────────────────────────────────────────────────────

src/ast-analysis/shared.ts

@@ -141,6 +141,10 @@ export const DATAFLOW_DEFAULTS: DataflowRulesConfig = {
   // Arrow/`=>`-style implicit-return body (issue #2356)
   implicitReturnBodyNode: null,
   blockBodyNode: 'block',
+
+  // Fieldless call structure override (issue #2357)
+  resolveCallParts: null,
+  callChainSiblingType: null,
 };
 
 export function makeDataflowRules(overrides: Partial<DataflowRulesConfig>): DataflowRulesConfig {

src/ast-analysis/visitors/dataflow-visitor.ts

@@ -207,6 +207,65 @@ function recordSimpleAssignment(
   scope.locals.set(varName, { type: 'call_return', callee });
 }
 
+/**
+ * Resolve a call node's callee name and argument-list node, using the
+ * language's `resolveCallParts` override when set (issue #2357 — grammars
+ * like tree-sitter-dart's `postfix_expression` have no field-based
+ * `callFunctionField`/`callArgsField` structure to read from a single
+ * self-contained node), falling back to the default field-based lookup
+ * (`resolveCalleeName` + `childForFieldName(callArgsField)`) otherwise.
+ */
+function resolveCallExprParts(
+  node: TreeSitterNode,
+  rules: AnyRules,
+): { callee: string; argsNode: TreeSitterNode } | null {
+  if (rules.resolveCallParts) return rules.resolveCallParts(node);
+  const callee = resolveCalleeName(node, rules);
+  const argsNode = node.childForFieldName(rules.callArgsField);
+  if (!callee || !argsNode) return null;
+  return { callee, argsNode };
+}
+
+/**
+ * Find the node `resolveCallExprParts` should be given for a value expression
+ * that MIGHT be call-sourced. For most languages `node` (already
+ * field-resolved to e.g. a `call_expression`) already IS the call node —
+ * `isCallNode(node.type)` returns it unchanged, exactly reproducing every
+ * existing caller's prior `isCall(node, isCallNode) ? node : null` check
+ * with zero behavior change.
+ *
+ * For a grammar whose call-node dispatch target is a SIBLING of the value
+ * expression rather than the value expression itself (tree-sitter-dart's
+ * `selector`, resolved backward from the callee — see `resolveDartCallParts`,
+ * issue #2357), `node` is instead the callee's own base expression (e.g. the
+ * bare `identifier` a var's `value` field resolves to for `var x =
+ * helper(y);`). This walks FORWARD through `node`'s sibling chain — a call's
+ * argument-list selector is always last in tree-sitter-dart's flat sibling
+ * sequence — to find the trailing call-node sibling, the symmetric
+ * counterpart of `resolveDartCallParts`'s backward walk. Returns null when
+ * no call-node sibling follows (a non-call value expression).
+ */
+function findCallSelector(
+  node: TreeSitterNode,
+  rules: AnyRules,
+  isCallNode: (t: string) => boolean,
+): TreeSitterNode | null {
+  if (isCallNode(node.type)) return node;
+  if (!rules.callChainSiblingType) return null;
+  let sib: TreeSitterNode | null = node.nextSibling;
+  let last: TreeSitterNode | null = null;
+  while (sib) {
+    if (!sib.isNamed) {
+      sib = sib.nextSibling;
+      continue;
+    }
+    if (sib.type !== rules.callChainSiblingType) break;
+    last = sib;
+    sib = sib.nextSibling;
+  }
+  return last && isCallNode(last.type) ? last : null;
+}
+
 function handleVarDeclarator(
   node: TreeSitterNode,
   rules: AnyRules,
@@ -222,11 +281,12 @@ function handleVarDeclarator(
   if (!nameNode || !valueNode || !scope) return;
 
   const unwrapped = unwrapAwait(valueNode, rules);
-  const callExpr = isCall(unwrapped, isCallNode) ? unwrapped : null;
+  const callExpr = findCallSelector(unwrapped, rules, isCallNode);
   if (!callExpr) return;
 
-  const callee = resolveCalleeName(callExpr, rules);
-  if (!callee || !scope.funcName) return;
+  const parts = resolveCallExprParts(callExpr, rules);
+  if (!parts || !scope.funcName) return;
+  const { callee } = parts;
 
   const isDestructured =
     (rules.objectDestructType && nameNode.type === rules.objectDestructType) ||
@@ -315,10 +375,10 @@ function handleCallExpr(
   scopeStack: ScopeEntry[],
   argFlows: DataflowArgFlow[],
 ): void {
-  const callee = resolveCalleeName(node, rules);
-  const argsNode = node.childForFieldName(rules.callArgsField);
+  const parts = resolveCallExprParts(node, rules);
   const scope = currentScope(scopeStack);
-  if (!callee || !argsNode || !scope?.funcName) return;
+  if (!parts || !scope?.funcName) return;
+  const { callee, argsNode } = parts;
 
   let argIndex = 0;
   for (const arg of argsNode.namedChildren) {

src/types.ts

@@ -1396,6 +1396,36 @@ export interface DataflowRulesConfig {
   implicitReturnBodyNode: string | null;
   /** The "real" statement-block wrapper type `implicitReturnBodyNode` is compared against. */
   blockBodyNode: string;
+  /**
+   * Override for grammars where a call has no field-based (`callFunctionField`/
+   * `callArgsField`) structure to read from a single self-contained node —
+   * e.g. tree-sitter-dart, which has no `call_expression` node type, AND
+   * whose grammar-documented `postfix_expression` wrapper never actually
+   * appears in a parsed tree either: a call is a FLAT SEQUENCE OF SIBLINGS
+   * (a base expression followed by a chain of `selector` siblings, one of
+   * which wraps an `argument_part` when it's a call — issue #2357). When
+   * set, this replaces the default `resolveCalleeName` +
+   * `childForFieldName(callArgsField)` lookup everywhere a call's
+   * callee/argument-list is resolved. Returns `null` when `node` isn't
+   * actually a call (e.g. Dart's `selector` also represents non-call member
+   * access and `x++`/`x--`).
+   */
+  resolveCallParts:
+    | ((node: TreeSitterNode) => { callee: string; argsNode: TreeSitterNode } | null)
+    | null;
+  /**
+   * The sibling node type `resolveCallParts`-style grammars chain calls
+   * through (Dart: `'selector'`). Lets `findCallSelector` (dataflow-visitor.ts)
+   * walk FORWARD from a call's base expression — resolved via the normal
+   * `varValueField`/`callFunctionField` lookup, landing on the base rather
+   * than the call itself in these grammars — to the trailing call-node
+   * sibling, so a call-sourced variable assignment (`var x = helper(y);`)
+   * is recognized the same way it already is for languages whose call node
+   * IS the value node directly (issue #2357). `null` for those languages:
+   * `findCallSelector` short-circuits via `isCallNode(node.type)` before
+   * ever consulting this field.
+   */
+  callChainSiblingType: string | null;
 }
 
 /** Language rule module: exports from each language rule file. */

tests/parsers/dataflow-dart.test.ts

@@ -144,4 +144,66 @@ describe('extractDataflow — Dart', () => {
       expect(multiplyReturns).toHaveLength(1);
     });
   });
+
+  // Issue #2357: tree-sitter-dart has no call_expression node type at all,
+  // and its documented postfix_expression wrapper never actually appears in
+  // a parsed tree either — a call is a flat sequence of siblings (a base
+  // expression followed by a chain of `selector` siblings, one of which
+  // wraps an argument_part when it's a call). callNode/resolveCallParts and
+  // the argument-wrapper config were entirely unset, so argFlows (and any
+  // call-derived dataflow) was always empty regardless of the sibling-body
+  // and return fixes above.
+  describe('calls', () => {
+    it('tracks a bare call argument flow (helper(x) as a return expression)', () => {
+      const data = parseAndExtract('int square(int x) {\n  return helper(x);\n}\n');
+      expect(data!.argFlows).toEqual(
+        expect.arrayContaining([
+          expect.objectContaining({ callerFunc: 'square', calleeName: 'helper', argName: 'x' }),
+        ]),
+      );
+    });
+
+    it('tracks a bare statement-level call argument flow', () => {
+      const data = parseAndExtract('int square(int x) {\n  helper(x);\n  return x;\n}\n');
+      expect(data!.argFlows).toEqual(
+        expect.arrayContaining([
+          expect.objectContaining({ callerFunc: 'square', calleeName: 'helper', argName: 'x' }),
+        ]),
+      );
+    });
+
+    it('tracks a method-call argument flow, resolving the callee via the preceding property selector', () => {
+      const data = parseAndExtract(
+        'class Obj {\n  int method(int x) => x;\n}\nint square(Obj obj, int x) {\n  return obj.method(x);\n}\n',
+      );
+      expect(data!.argFlows).toEqual(
+        expect.arrayContaining([
+          expect.objectContaining({ callerFunc: 'square', calleeName: 'method', argName: 'x' }),
+        ]),
+      );
+    });
+
+    it('does not misidentify a non-call postfix expression (x++) as a call', () => {
+      const data = parseAndExtract('int inc(int x) {\n  x++;\n  return x;\n}\n');
+      expect(data!.argFlows).toEqual([]);
+    });
+  });
+
+  describe('assignments', () => {
+    it('tracks a call-sourced variable assignment (var x = helper(y))', () => {
+      const data = parseAndExtract('int square(int y) {\n  var x = helper(y);\n  return x;\n}\n');
+      expect(data!.assignments).toEqual(
+        expect.arrayContaining([
+          expect.objectContaining({ varName: 'x', callerFunc: 'square', sourceCallName: 'helper' }),
+        ]),
+      );
+    });
+
+    it('does not record a plain (non-call-sourced) variable declaration as an assignment', () => {
+      const data = parseAndExtract(
+        'int add(int a, int b) {\n  var sum = a + b;\n  return sum;\n}\n',
+      );
+      expect(data!.assignments).toEqual([]);
+    });
+  });
 });