fix(erlang): resolve selective imports by arity

CHANGELOG.md

@@ -27,7 +27,7 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### Fixes
 
-- Erlang functions that share a name but differ in arity are now separate symbols with the language's own `module:fun/arity` identity, so the everyday `f/1` delegating to `f/2` shows as a real call edge instead of a self-loop, each arity keeps its own `-spec` and source span, `-export([f/1])` marks exactly that arity as public, and asking `codegraph_explore` for a symbol the way Erlang spells it — `cowboy_req:header/3` — returns that definition. Re-index Erlang projects after upgrading. Thanks @Dshuishui. (#1610) (Erlang)
+- Erlang functions that share a name but differ in arity are now separate symbols with the language's own `module:fun/arity` identity, so the everyday `f/1` delegating to `f/2` shows as a real call edge instead of a self-loop, each arity keeps its own `-spec` and source span, `-export([f/1])` marks exactly that arity as public, and asking `codegraph_explore` for a symbol the way Erlang spells it — `cowboy_req:header/3` — returns that definition. Selective `-import` calls now resolve only to the named module, while built-in and otherwise out-of-scope calls stay unresolved instead of linking to an unrelated project function with the same name. Re-index Erlang projects after upgrading. Thanks @Dshuishui. (#1610) (Erlang)
 
 - Erlang behaviour dispatch no longer miscounts a call site's arity when an argument is a binary literal like `<<1,2,3>>` — the commas inside were counted as argument separators, which silently dropped (or could mislink) the dispatch edge to the behaviour callback. (#1358) (Erlang)
 - The MCP server now finds your project when it's launched from a workspace folder above it: if the launch directory has no index of its own but exactly one indexed project sits below it (a repo container, an agent workspace, a monorepo root), that project becomes the session's default — live file watching and the shared daemon included — instead of every tool call failing until a `projectPath` or `--path` is supplied. Thanks @nakisen. (#1606)

__tests__/erlang-arity-resolution.test.ts

@@ -144,4 +144,60 @@ run(L) ->
     expect(edges).toContainEqual({ sq: 'user_m::run/1', tq: 'lib_m::bump/1' });
     expect(edges.some((e) => e.sq === 'user_m::run/1' && e.tq === 'lib_m::bump/2')).toBe(false);
   });
+
+  it('resolves a selective import to its named module, not a nearer same-named function', async () => {
+    fs.mkdirSync(path.join(dir, 'deps'), { recursive: true });
+    fs.mkdirSync(path.join(dir, 'app'), { recursive: true });
+    fs.writeFileSync(
+      path.join(dir, 'deps', 'imported.erl'),
+      `-module(imported).
+-export([pick/1]).
+
+pick(X) -> {imported, X}.
+`
+    );
+    fs.writeFileSync(
+      path.join(dir, 'app', 'wrong.erl'),
+      `-module(wrong).
+-export([pick/1]).
+
+pick(X) -> {wrong, X}.
+`
+    );
+    fs.writeFileSync(
+      path.join(dir, 'app', 'client.erl'),
+      `-module(client).
+-import(imported, [
+    pick/1 % imported selectively
+]).
+-export([run/1]).
+
+run(X) -> pick(X).
+`
+    );
+    const edges = await callEdges(dir);
+    expect(edges).toContainEqual({ sq: 'client::run/1', tq: 'imported::pick/1' });
+    expect(edges).not.toContainEqual({ sq: 'client::run/1', tq: 'wrong::pick/1' });
+  });
+
+  it('does not bind an auto-imported BIF to a same-named project function', async () => {
+    fs.writeFileSync(
+      path.join(dir, 'other.erl'),
+      `-module(other).
+-export([length/1]).
+
+length(X) -> X.
+`
+    );
+    fs.writeFileSync(
+      path.join(dir, 'client.erl'),
+      `-module(client).
+-export([run/1]).
+
+run(X) -> length(X).
+`
+    );
+    const edges = await callEdges(dir);
+    expect(edges).not.toContainEqual({ sq: 'client::run/1', tq: 'other::length/1' });
+  });
 });

src/extraction/extraction-version.ts

@@ -21,4 +21,4 @@
  * turns the re-index hint into noise — keep it honest (see CLAUDE.md, "Honesty
  * in the product is load-bearing").
  */
-export const EXTRACTION_VERSION = 25;
+export const EXTRACTION_VERSION = 26;

src/resolution/import-resolver.ts

@@ -788,11 +788,75 @@ export function extractImportMappings(
     mappings.push(...extractPHPImports(content));
   } else if (language === 'c' || language === 'cpp') {
     mappings.push(...extractCppImports(content));
+  } else if (language === 'erlang') {
+    mappings.push(...extractErlangImports(content));
   }
 
   return mappings;
 }
 
+/**
+ * Extract Erlang's selective imports: `-import(module, [f/1, g/2]).`
+ *
+ * The arity stays in the local/exported name because it is part of an Erlang
+ * function's identity. The module name is an atom, not a filesystem path; the
+ * Erlang branch in resolveViaImport uses it to form the qualified name.
+ */
+function extractErlangImports(content: string): ImportMapping[] {
+  const mappings: ImportMapping[] = [];
+  const atom = String.raw`(?:'(?:\\.|[^'])*'|[a-z][A-Za-z0-9_@]*)`;
+  const importRe = new RegExp(
+    String.raw`^\s*-import\s*\(\s*(${atom})\s*,\s*\[([\s\S]*?)\]\s*\)\s*\.`,
+    'gm',
+  );
+  const bindingRe = new RegExp(String.raw`(${atom})\s*\/\s*(\d{1,3})`, 'g');
+  const unquoteAtom = (value: string): string => value.replace(/^'([\s\S]*)'$/, '$1');
+
+  let importMatch: RegExpExecArray | null;
+  while ((importMatch = importRe.exec(content)) !== null) {
+    const source = unquoteAtom(importMatch[1]!);
+    const bindings = stripErlangLineComments(importMatch[2]!);
+    bindingRe.lastIndex = 0;
+    let bindingMatch: RegExpExecArray | null;
+    while ((bindingMatch = bindingRe.exec(bindings)) !== null) {
+      const name = `${unquoteAtom(bindingMatch[1]!)}/${bindingMatch[2]}`;
+      mappings.push({
+        localName: name,
+        exportedName: name,
+        source,
+        isDefault: false,
+        isNamespace: false,
+      });
+    }
+  }
+
+  return mappings;
+}
+
+/** Strip `%` comments without treating a percent inside a quoted atom/string as a comment. */
+function stripErlangLineComments(value: string): string {
+  let result = '';
+  let quote: "'" | '"' | null = null;
+  let escaped = false;
+  for (let i = 0; i < value.length; i++) {
+    const ch = value[i]!;
+    if (quote) {
+      result += ch;
+      if (escaped) escaped = false;
+      else if (ch === '\\') escaped = true;
+      else if (ch === quote) quote = null;
+    } else if (ch === "'" || ch === '"') {
+      quote = ch;
+      result += ch;
+    } else if (ch === '%') {
+      while (i + 1 < value.length && value[i + 1] !== '\n') i++;
+    } else {
+      result += ch;
+    }
+  }
+  return result;
+}
+
 /**
  * Extract JS/TS import mappings
  */
@@ -1433,6 +1497,31 @@ export function resolveViaImport(
     return null;
   }
 
+  // Erlang selective imports name a module rather than a filesystem path, and
+  // the imported binding includes its arity (`-import(a, [f/1])`). Resolve the
+  // exact module::function/arity identity before the generic path-based import
+  // logic. Ambiguous duplicate module definitions are left unresolved.
+  if (ref.language === 'erlang' && /^.+\/\d{1,3}$/.test(ref.referenceName)) {
+    const imp = imports.find((candidate) => candidate.localName === ref.referenceName);
+    if (imp) {
+      const candidates = context
+        .getNodesByQualifiedName(`${imp.source}::${imp.exportedName}`)
+        .filter(
+          (node) =>
+            node.language === 'erlang' && node.kind === 'function' && node.isExported,
+        );
+      if (candidates.length === 1) {
+        return {
+          original: ref,
+          targetNodeId: candidates[0]!.id,
+          confidence: 0.95,
+          resolvedBy: 'import',
+        };
+      }
+    }
+    return null;
+  }
+
   // Go cross-package calls: `pkga.FuncX(...)` extracts to referenceName
   // `pkga.FuncX` and the import `github.com/example/myproject/pkga`
   // maps to a *package directory* containing one or more .go files.

src/resolution/name-matcher.ts

@@ -2551,11 +2551,10 @@ export function matchReference(
   // Erlang call/fun refs carry the call-site arity (`f/1` — #1610) because
   // arity is part of the function's identity and every erlang function's
   // qualifiedName carries it (`mod::f/1`). Resolve ONLY to a definition of
-  // that exact arity: the call site's own file first (a local call targets its
-  // own module by language semantics; `-import`ed functions ride the
-  // cross-file branch), and when no definition of that arity exists anywhere,
-  // resolve to NOTHING rather than a sibling arity — the real target may be
-  // macro-generated or out of repo, and a wrong-arity edge is worse than none.
+  // that exact arity in the call site's own module. Explicit `-import`s are
+  // handled by resolveViaImport before this matcher. A bare call can otherwise
+  // only be a local function or an auto-imported BIF, so it must never fall
+  // through to a same-named function in another module.
   if (
     ref.language === 'erlang' &&
     !ref.referenceName.includes('::') &&
@@ -2565,30 +2564,17 @@ export function matchReference(
     if (am) {
       // endsWith is length-anchored, so `/1` cannot match `…/11`.
       const arityTail = `/${am[2]}`;
-      const candidates = context
-        .getNodesByName(am[1]!)
-        .filter(
+      const sameFile = context
+        .getNodesInFile(ref.filePath)
+        .find(
           (n) =>
-            n.language === 'erlang' && n.kind === 'function' && n.qualifiedName.endsWith(arityTail),
+            n.language === 'erlang' &&
+            n.kind === 'function' &&
+            n.name === am[1] &&
+            n.qualifiedName.endsWith(arityTail),
         );
-      if (candidates.length > 0) {
-        const sameFile = candidates.find((n) => n.filePath === ref.filePath);
-        if (sameFile) {
-          return { original: ref, targetNodeId: sameFile.id, confidence: 0.95, resolvedBy: 'exact-match' };
-        }
-        if (candidates.length === 1) {
-          return { original: ref, targetNodeId: candidates[0]!.id, confidence: 0.8, resolvedBy: 'exact-match' };
-        }
-        const best = findBestMatch(ref, candidates, context);
-        if (best) {
-          const proximity = computePathProximity(ref.filePath, best.filePath);
-          return {
-            original: ref,
-            targetNodeId: best.id,
-            confidence: proximity >= 30 ? 0.7 : 0.4,
-            resolvedBy: 'exact-match',
-          };
-        }
+      if (sameFile) {
+        return { original: ref, targetNodeId: sameFile.id, confidence: 0.95, resolvedBy: 'exact-match' };
       }
       return null;
     }