feat(extraction): Erlang macro-body call linkage (#635, #648)

Calls hidden inside -define bodies were invisible: the extractor consumed
pp_define without walking the replacement, and macro use sites produced no
edges, so a call path routed through a macro (ejabberd's SQL upsert macros,
logging wrappers) was completely dark.

The macro's constant node now participates in the graph. The -define body's
calls are attributed to the MACRO — true exactly once, instead of a per-use
duplicate that would explode on logging macros — and each use site links
in: ?MACRO(...) with arguments emits a `calls` ref (inlined code joins the
call chain), a bare ?CONSTANT read emits `references` (answering "where is
this macro used" without polluting call paths). Compiler-predefined macros
(?MODULE, ?LINE, ?FUNCTION_NAME, ...) are excluded, macro-use arguments
keep walking so a call nested in ?assertEqual(ok, do_thing()) still
attributes to the enclosing function, and macro-to-macro chains connect.

Validated: node counts unchanged on cowboy/ejabberd/emqx; edges +26/+7.3K/
+42K with honest hub shapes (?T i18n, ?SLOG logging, ?QOS_1 protocol
constants); 40/40 sampled edges precise; +1.3s index cost on emqx's 2,273
files. The payoff chain on ejabberd: set_password_scram_t → ?SQL_UPSERT_T →
ejabberd_sql:sql_query_t — database writes through SQL macros now trace
end-to-end.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

__tests__/extraction.test.ts

@@ -9134,6 +9134,81 @@ second(X) -> X.
     });
   });
 
+  describe('Macro linkage', () => {
+    it('should attribute macro-body calls to the macro and link function-like uses into the chain', () => {
+      const code = `-module(m).
+-export([do_thing/1]).
+
+-define(LOG_AUDIT(Event), audit_logger:log(Event, ?MODULE)).
+
+do_thing(X) ->
+    ?LOG_AUDIT({thing, X}),
+    ok.
+`;
+      const result = extractFromSource('src/m.erl', code);
+      const macro = result.nodes.find((n) => n.kind === 'constant' && n.name === 'LOG_AUDIT');
+      const doThing = result.nodes.find((n) => n.kind === 'function' && n.name === 'do_thing');
+      const refsFrom = (id?: string) =>
+        result.unresolvedReferences.filter((r) => r.fromNodeId === id).map((r) => `${r.referenceKind}:${r.referenceName}`);
+      // The body's remote call belongs to the macro node — true exactly once.
+      expect(refsFrom(macro?.id)).toContain('calls:audit_logger::log');
+      // The use site joins the call chain: do_thing -calls→ LOG_AUDIT.
+      expect(refsFrom(doThing?.id)).toContain('calls:LOG_AUDIT');
+    });
+
+    it('should reference bare macro reads without polluting call chains', () => {
+      const code = `-module(m).
+-export([wait/0]).
+
+-define(TIMEOUT, 5000).
+
+wait() ->
+    receive after ?TIMEOUT -> ok end.
+`;
+      const result = extractFromSource('src/m.erl', code);
+      const refs = result.unresolvedReferences.map((r) => `${r.referenceKind}:${r.referenceName}`);
+      expect(refs).toContain('references:TIMEOUT');
+      expect(refs).not.toContain('calls:TIMEOUT');
+    });
+
+    it('should skip compiler-predefined macros and keep walking macro-use arguments', () => {
+      const code = `-module(m).
+-export([check/0]).
+
+check() ->
+    ?assertEqual(ok, prepare()),
+    {?MODULE, ?LINE, ?FUNCTION_NAME}.
+
+prepare() -> ok.
+`;
+      const result = extractFromSource('src/m.erl', code);
+      const refs = result.unresolvedReferences.map((r) => r.referenceName);
+      // The nested call inside the macro's arguments still attributes to check/0.
+      expect(refs).toContain('prepare');
+      // ?assertEqual (an OTP header macro) is emitted and simply never resolves…
+      expect(refs).toContain('assertEqual');
+      // …but predefined macros have no definition to link.
+      expect(refs).not.toContain('MODULE');
+      expect(refs).not.toContain('LINE');
+      expect(refs).not.toContain('FUNCTION_NAME');
+    });
+
+    it('should chain macro-to-macro uses', () => {
+      const code = `-module(m).
+
+-define(TARGET, target_fn()).
+-define(ALIAS, ?TARGET).
+`;
+      const result = extractFromSource('src/m.erl', code);
+      const target = result.nodes.find((n) => n.kind === 'constant' && n.name === 'TARGET');
+      const alias = result.nodes.find((n) => n.kind === 'constant' && n.name === 'ALIAS');
+      const refsFrom = (id?: string) =>
+        result.unresolvedReferences.filter((r) => r.fromNodeId === id).map((r) => `${r.referenceKind}:${r.referenceName}`);
+      expect(refsFrom(target?.id)).toContain('calls:target_fn');
+      expect(refsFrom(alias?.id)).toContain('references:TARGET');
+    });
+  });
+
   describe('Behaviour extraction', () => {
     it('should emit an implements reference for -behaviour', () => {
       const code = `-module(m).

src/extraction/languages/erlang.ts

@@ -175,12 +175,24 @@ function handleTypeAlias(node: SyntaxNode, ctx: ExtractorContext): boolean {
 function handlePpDefine(node: SyntaxNode, ctx: ExtractorContext): boolean {
   const lhs = getChildByField(node, 'lhs');
   const nameNode = lhs ? getChildByField(lhs, 'name') : null;
-  if (nameNode) {
-    ctx.createNode('constant', getNodeText(nameNode, ctx.source), node, {
-      signature: collapseWs(getNodeText(node, ctx.source)).slice(0, 200),
-    });
+  if (!nameNode) return true;
+  const macro = ctx.createNode('constant', getNodeText(nameNode, ctx.source), node, {
+    signature: collapseWs(getNodeText(node, ctx.source)).slice(0, 200),
+  });
+  // The replacement's calls execute at expansion sites, but attributing them
+  // to the MACRO node keeps them true exactly once: `-define(LOG_AUDIT(E),
+  // audit_logger:log(E))` gives the LOG_AUDIT constant a `calls` edge to the
+  // logger, and each `?LOG_AUDIT(...)` use site links to the constant (see the
+  // macro_call_expr case in extractCall) — so the chain
+  // `caller → LOG_AUDIT → audit_logger:log` traverses without minting a
+  // per-use duplicate of the body's calls.
+  const replacement = getChildByField(node, 'replacement');
+  if (macro && replacement) {
+    ctx.pushScope(macro.id);
+    ctx.visitFunctionBody(replacement, macro.id);
+    ctx.popScope();
   }
-  return true; // the replacement's calls only exist at expansion sites
+  return true;
 }
 
 function handleBehaviour(node: SyntaxNode, ctx: ExtractorContext): boolean {
@@ -218,6 +230,7 @@ export const erlangExtractor: LanguageExtractor = {
     'record_update_expr', // X#rec{...}
     'record_index_expr', // #rec.field
     'record_field_expr', // X#rec.field
+    'macro_call_expr', // ?MACRO / ?MACRO(...) — links use sites to the -define constant
   ],
   variableTypes: [],
   nameField: 'name',

src/extraction/tree-sitter.ts

@@ -67,6 +67,13 @@ const VUE_STORE_FILE_SIGNAL = /\bdefineStore\b|\bcreateStore\b|\bVuex\b|\bmutati
  * Used by the erlang branch of extractCall to lift a static MFA pair into a
  * call edge (the spawned/applied function is otherwise invisible to the graph).
  */
+/** Compiler-predefined Erlang macros — no `-define` exists to link a use to. */
+const ERLANG_PREDEFINED_MACROS = new Set([
+  'MODULE', 'MODULE_STRING', 'FILE', 'LINE', 'MACHINE',
+  'FUNCTION_NAME', 'FUNCTION_ARITY', 'OTP_RELEASE',
+  'FEATURE_AVAILABLE', 'FEATURE_ENABLED',
+]);
+
 const ERLANG_MFA_CALLS = new Set([
   'spawn', 'spawn_link', 'spawn_monitor', 'spawn_opt', 'apply',
   'erlang:spawn', 'erlang:spawn_link', 'erlang:spawn_monitor', 'erlang:spawn_opt', 'erlang:apply',
@@ -3752,6 +3759,29 @@ export class TreeSitterExtractor {
         });
         return;
       }
+      if (node.type === 'macro_call_expr') {
+        // Macro use site → the `-define` constant node. Function-like uses
+        // (`?LOG_AUDIT(X)` — args present) are inlined code, so they join the
+        // call chain and connect through the macro node to the body's calls
+        // (attributed there by handlePpDefine); bare reads (`?TIMEOUT`) are
+        // `references`, answering "where is this macro used" without
+        // polluting call paths. Compiler-predefined macros carry no
+        // definition to link. The use site's ARGUMENTS are children and keep
+        // walking, so a call nested in `?assertEqual(ok, do_thing())` still
+        // attributes to the enclosing function.
+        const macroName = getChildByField(node, 'name');
+        if (!macroName) return;
+        const name = getNodeText(macroName, this.source);
+        if (ERLANG_PREDEFINED_MACROS.has(name)) return;
+        this.unresolvedReferences.push({
+          fromNodeId: callerId,
+          referenceName: name,
+          referenceKind: getChildByField(node, 'args') ? 'calls' : 'references',
+          line,
+          column,
+        });
+        return;
+      }
       // record_expr / record_update_expr / record_index_expr / record_field_expr
       const recordName = getChildByField(node, 'name');
       const recordAtom = recordName?.type === 'record_name' ? getChildByField(recordName, 'name') : null;