fix(response) orphaned .wasm.map diagnostic misclassification

- Count `.wasm.map` files directly in `addWasmDiscoveryCounts` instead of only when a companion `.wasm` exists
- Widen the diagnostic walk to include `.map` so orphan wasm maps leave the JS `mapFiles` tally
- Add a `buildEmptyDiscoveryError` branch for wasm maps without modules, explaining the missing `.wasm` requirement
- Cover orphan and JS-map tally behavior in `wasm.test.ts`

Author: d2anamaria

packages/cli/src/lib/sourcemap/inject.ts

@@ -827,6 +827,17 @@ export function buildEmptyDiscoveryError(
       "directory"
     );
   }
+  // Wasm maps with no module beside them: the debug ID comes from the
+  // module's `build_id`, so the map alone is not uploadable.
+  if (jsFiles === 0 && mapFiles === 0 && wasmMaps > 0 && wasmFiles === 0) {
+    return new ValidationError(
+      `Found ${wasmMaps} .wasm.map file(s) in '${dir}' but no .wasm ` +
+        "modules. A wasm sourcemap is matched to its module's build_id, so " +
+        "the .wasm file must sit beside it — point the command at your " +
+        "build output. Pass --allow-empty to suppress.",
+      "directory"
+    );
+  }
   if (jsFiles === 0 && mapFiles === 0) {
     return new ValidationError(
       `Directory '${dir}' contains no JS or sourcemap files. ` +

packages/cli/src/lib/sourcemap/wasm.ts

@@ -40,6 +40,16 @@ const log = logger.withTag("sourcemap.wasm");
  */
 const WASM_EXTENSIONS: ReadonlySet<string> = new Set([".wasm"]);
 
+/**
+ * Extensions scanned when counting artifacts for the zero-pairs diagnostic.
+ * Covers `.map` so an orphaned `app.wasm.map` — a map whose module is not in
+ * the directory — is attributed to wasm instead of being left in the JS tally.
+ */
+const WASM_DIAGNOSTIC_EXTENSIONS: ReadonlySet<string> = new Set([
+  ".wasm",
+  ".map",
+]);
+
 /** A WebAssembly module and the sourcemap sitting next to it. */
 export type WasmPair = {
   /** Absolute path to the `.wasm` module. */
@@ -178,7 +188,9 @@ export async function discoverWasmPairs(
  * Only called on the zero-pairs error path, so a second walk costs nothing
  * that matters. `.wasm.map` files are moved out of the JS `mapFiles` tally —
  * the JS walk counts every `.map` — so the JS branches of
- * `buildEmptyDiscoveryError` keep describing JS alone.
+ * `buildEmptyDiscoveryError` keep describing JS alone. Maps are counted
+ * independently of modules, so a map left behind by a missing module is still
+ * recognised as wasm.
  *
  * @param dir - Directory to scan
  * @param js - The diagnostic from `diagnoseEmptyDiscovery`
@@ -191,10 +203,17 @@ export async function addWasmDiscoveryCounts(
   const absDir = resolvePath(dir);
   let wasmFiles = 0;
   let wasmMaps = 0;
-  for await (const wasmPath of walkWasmModules(absDir)) {
-    wasmFiles += 1;
-    if (await hasCompanionMap(`${wasmPath}.map`)) {
+  for await (const path of walkWasmModules(
+    absDir,
+    undefined,
+    WASM_DIAGNOSTIC_EXTENSIONS
+  )) {
+    // The widened extension set also yields JS `.map` files; those stay in the
+    // JS tally.
+    if (path.endsWith(".wasm.map")) {
       wasmMaps += 1;
+    } else if (path.endsWith(".wasm")) {
+      wasmFiles += 1;
     }
   }
   return {
@@ -211,14 +230,18 @@ export async function addWasmDiscoveryCounts(
  * Uses the same traversal settings as JS discovery — build outputs are usually
  * gitignored, `dist`/`build` must not be pruned, and a wasm module easily
  * exceeds any size cap.
+ *
+ * @param extensions - Widened only by the diagnostic walk, which also needs
+ * `.map` files; callers must then filter the extra extensions themselves.
  */
 async function* walkWasmModules(
   absDir: string,
-  ignoreMatcher?: ReturnType<typeof ignore>
+  ignoreMatcher?: ReturnType<typeof ignore>,
+  extensions: ReadonlySet<string> = WASM_EXTENSIONS
 ): AsyncGenerator<string> {
   for await (const entry of walkFiles({
     cwd: absDir,
-    extensions: WASM_EXTENSIONS,
+    extensions,
     alwaysSkipDirs: SOURCEMAP_SKIP_DIRS,
     hidden: false,
     respectGitignore: false,

packages/cli/test/lib/sourcemap/wasm.test.ts

@@ -11,6 +11,7 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 import ignore from "ignore";
 import { beforeEach, describe, expect, test } from "vitest";
+import { buildEmptyDiscoveryError } from "../../../src/lib/sourcemap/inject.js";
 import {
   addWasmDiscoveryCounts,
   discoverWasmPairs,
@@ -255,4 +256,35 @@ describe("addWasmDiscoveryCounts", () => {
     expect(diag.wasmFiles).toBe(1);
     expect(diag.wasmMaps).toBe(0);
   });
+
+  test("attributes a map with no module to wasm, not JS", async () => {
+    await writeMap("app.wasm.map");
+
+    const diag = await addWasmDiscoveryCounts(dir, {
+      jsFiles: 0,
+      mapFiles: 1,
+    });
+
+    expect(diag).toEqual({
+      jsFiles: 0,
+      mapFiles: 0,
+      wasmFiles: 0,
+      wasmMaps: 1,
+    });
+    expect(buildEmptyDiscoveryError(dir, diag).message).toContain(
+      "1 .wasm.map file(s)"
+    );
+  });
+
+  test("leaves JS maps in the JS tally", async () => {
+    await writeMap("app.js.map");
+
+    const diag = await addWasmDiscoveryCounts(dir, {
+      jsFiles: 0,
+      mapFiles: 1,
+    });
+
+    expect(diag.mapFiles).toBe(1);
+    expect(diag.wasmMaps).toBe(0);
+  });
 });