fix(javascript): keep Vite dependency slots after a spread unknown (#4023)

The __vite__mapDeps table indexer mapped a spread element to one unknown slot, so every later entry kept a definite index even though the spread can add any number of elements. A call such as __vite__mapDeps([0, 2]) over ["./first.js", ...["./middle-a.js", "./middle-b.js"], "./last.js"] then resolved index 2 to last.js instead of middle-b.js. Keep only the entries before the first spread; indexes from the spread onward stay unknown.

src/domain/javascript/javascriptStaticAnalysisCalls.ts

@@ -398,7 +398,14 @@ export const indexVitePreloadDependencyTable = (
   if (tables.length !== 1) return [];
   const table = tables[0];
   if (table === undefined) return [];
-  const dependencies = table.elements.map((element) =>
+  // A spread contributes an unknown number of entries, so every later slot
+  // has an unknown index; leave those out instead of shifting them.
+  const spread = table.elements.findIndex((element) =>
+    t.isSpreadElement(element),
+  );
+  const dependencies = (
+    spread === -1 ? table.elements : table.elements.slice(0, spread)
+  ).map((element) =>
     element === null || t.isSpreadElement(element)
       ? undefined
       : stringValue(element),

src/domain/javascript/javascriptVitePreloadDependencies.test.ts

@@ -83,4 +83,19 @@ describe("Vite preload dependency recovery", () => {
         .map(({ specifier }) => specifier),
     ).toEqual(["./original.js"]);
   });
+
+  it("keeps table slots from a spread onward unknown", () => {
+    const analysis = analyzeJavaScriptStaticSource(`
+      const __vite__mapDeps = (indexes, map = __vite__mapDeps, dependencies =
+        (map.f || (map.f = ["./first.js", ...["./middle-a.js", "./middle-b.js"], "./last.js"]))) =>
+        indexes.map((index) => dependencies[index]);
+      __vite__mapDeps([0, 2]);
+    `);
+
+    expect(
+      analysis.references
+        .filter(({ kind }) => kind === "dynamic-import")
+        .map(({ specifier }) => specifier),
+    ).toEqual(["./first.js", null]);
+  });
 });