fix(javascript): preserve loader-specific package ancestry

Require a package directory for bare ESM imports. Continue CommonJS root and subpath lookup through ancestor packages after ordinary misses, while keeping exports authority, unavailable metadata, and failed nonempty main entrypoints terminal.

Carry failed-main ownership in the internal resolution result and retain the nearest local miss after exhausting ancestors. Consolidate package selection at its owning boundary and qualify loader differences with real Node 24, CLI, and MCP regressions.

tests/acceptance/applications/JavaScriptModuleLookupCli.test.ts

@@ -21,6 +21,10 @@ const createModuleLookupFixture = async () => {
       'import "./exact.js";',
       'import fallback from "empty-main";',
       'import "nested-main";',
+      'import "file-only";',
+      'import "ancestor-empty";',
+      'import "ancestor-blocked";',
+      'import "ancestor-sub/parser";',
       "void fallback;",
     ].join("\n"),
     "esm/extensionless.js": "module.exports = 1;",
@@ -36,6 +40,10 @@ const createModuleLookupFixture = async () => {
       'require("./default-node");',
       'require("empty-main");',
       'require("nested-main");',
+      'require("file-only");',
+      'require("ancestor-empty");',
+      'require("ancestor-blocked");',
+      'require("ancestor-sub/parser");',
     ].join("\n"),
     "cjs/extensionless.cjs": "module.exports = 1;",
     "cjs/feature.cjs": "module.exports = 2;",
@@ -50,8 +58,12 @@ const createModuleLookupFixture = async () => {
       main: "other",
     }),
     "node_modules/nested-main/sub/other.js": "module.exports = 99;",
-    "runtime-control.mjs": [
-      'const specifiers = ["./esm/extensionless", "./esm/directory", "./esm/explicit.js", "./esm/exact.js", "empty-main", "nested-main"];',
+    "node_modules/file-only.js": "module.exports = 7;",
+    "node_modules/ancestor-empty/index.js": "module.exports = 8;",
+    "node_modules/ancestor-blocked/index.js": "module.exports = 9;",
+    "node_modules/ancestor-sub/parser.js": "module.exports = 10;",
+    "esm/runtime-control.mjs": [
+      'const specifiers = ["./extensionless", "./directory", "./explicit.js", "./exact.js", "empty-main", "nested-main", "file-only", "ancestor-empty", "ancestor-blocked", "ancestor-sub/parser"];',
       "const results = [];",
       "for (const specifier of specifiers) {",
       "  try { await import(specifier); results.push({ specifier, ok: true }); }",
@@ -59,8 +71,8 @@ const createModuleLookupFixture = async () => {
       "}",
       "console.log(JSON.stringify(results));",
     ].join("\n"),
-    "runtime-control.cjs": [
-      'const specifiers = ["./cjs/extensionless", "./cjs/feature", "./cjs/feature.cjs", "./cjs/default-js", "./cjs/default-json", "empty-main", "nested-main"];',
+    "cjs/runtime-control.cjs": [
+      'const specifiers = ["./extensionless", "./feature", "./feature.cjs", "./default-js", "./default-json", "empty-main", "nested-main", "file-only", "ancestor-empty", "ancestor-blocked", "ancestor-sub/parser"];',
       "const results = [];",
       "for (const specifier of specifiers) {",
       "  try { require(specifier); results.push({ specifier, ok: true }); }",
@@ -69,6 +81,15 @@ const createModuleLookupFixture = async () => {
       "console.log(JSON.stringify(results));",
     ].join("\n"),
   });
+  for (const directory of ["esm", "cjs"])
+    await writeFixtureFiles(root, {
+      [`${directory}/node_modules/ancestor-empty/package.json`]: JSON.stringify(
+        { main: "" },
+      ),
+      [`${directory}/node_modules/ancestor-blocked/package.json`]:
+        JSON.stringify({ main: "missing" }),
+      [`${directory}/node_modules/ancestor-sub/package.json`]: "{}",
+    });
   return root;
 };
 
@@ -77,11 +98,11 @@ cliTest.for(["CLI", "stdio MCP"] as const)(
   async (surface, { cli }) => {
     const root = await createModuleLookupFixture();
     const [esmControl, cjsControl] = await Promise.all([
-      execute(process.execPath, ["runtime-control.mjs"], {
+      execute(process.execPath, ["esm/runtime-control.mjs"], {
         cwd: root,
         timeout: 5_000,
       }),
-      execute(process.execPath, ["runtime-control.cjs"], {
+      execute(process.execPath, ["cjs/runtime-control.cjs"], {
         cwd: root,
         timeout: 5_000,
       }),
@@ -98,40 +119,56 @@ cliTest.for(["CLI", "stdio MCP"] as const)(
     }>;
     expect(esmResults).toEqual([
       {
-        specifier: "./esm/extensionless",
+        specifier: "./extensionless",
         ok: false,
         code: "ERR_MODULE_NOT_FOUND",
       },
       {
-        specifier: "./esm/directory",
+        specifier: "./directory",
         ok: false,
         code: "ERR_UNSUPPORTED_DIR_IMPORT",
       },
       {
-        specifier: "./esm/explicit.js",
+        specifier: "./explicit.js",
         ok: false,
         code: "ERR_MODULE_NOT_FOUND",
       },
-      { specifier: "./esm/exact.js", ok: true },
+      { specifier: "./exact.js", ok: true },
       { specifier: "empty-main", ok: true },
       { specifier: "nested-main", ok: false, code: "ERR_MODULE_NOT_FOUND" },
+      { specifier: "file-only", ok: false, code: "ERR_MODULE_NOT_FOUND" },
+      { specifier: "ancestor-empty", ok: false, code: "ERR_MODULE_NOT_FOUND" },
+      {
+        specifier: "ancestor-blocked",
+        ok: false,
+        code: "ERR_MODULE_NOT_FOUND",
+      },
+      {
+        specifier: "ancestor-sub/parser",
+        ok: false,
+        code: "ERR_MODULE_NOT_FOUND",
+      },
     ]);
     expect(cjsResults).toEqual([
       {
-        specifier: "./cjs/extensionless",
+        specifier: "./extensionless",
         ok: false,
         code: "MODULE_NOT_FOUND",
       },
       {
-        specifier: "./cjs/feature",
+        specifier: "./feature",
         ok: false,
         code: "MODULE_NOT_FOUND",
       },
-      { specifier: "./cjs/feature.cjs", ok: true },
-      { specifier: "./cjs/default-js", ok: true },
-      { specifier: "./cjs/default-json", ok: true },
+      { specifier: "./feature.cjs", ok: true },
+      { specifier: "./default-js", ok: true },
+      { specifier: "./default-json", ok: true },
       { specifier: "empty-main", ok: true },
       { specifier: "nested-main", ok: false, code: "MODULE_NOT_FOUND" },
+      { specifier: "file-only", ok: true },
+      { specifier: "ancestor-empty", ok: true },
+      { specifier: "ancestor-blocked", ok: false, code: "MODULE_NOT_FOUND" },
+      { specifier: "ancestor-sub/parser", ok: true },
     ]);
 
     const { graph } = await analyzeJavaScriptDirectory(surface, cli, root);
@@ -142,6 +179,10 @@ cliTest.for(["CLI", "stdio MCP"] as const)(
       ["import", "./exact.js", "esm/exact.js", "resolved"],
       ["import", "empty-main", "node_modules/empty-main/index.js", "resolved"],
       ["import", "nested-main", null, "not-found"],
+      ["import", "file-only", null, "external"],
+      ["import", "ancestor-empty", null, "not-found"],
+      ["import", "ancestor-blocked", null, "not-found"],
+      ["import", "ancestor-sub/parser", null, "not-found"],
       ["require", "./extensionless", null, "not-found"],
       ["require", "./feature", null, "not-found"],
       ["require", "./feature.cjs", "cjs/feature.cjs", "resolved"],
@@ -150,6 +191,20 @@ cliTest.for(["CLI", "stdio MCP"] as const)(
       ["require", "./default-node", "cjs/default-node.node", "resolved"],
       ["require", "empty-main", "node_modules/empty-main/index.js", "resolved"],
       ["require", "nested-main", null, "not-found"],
+      ["require", "file-only", "node_modules/file-only.js", "resolved"],
+      [
+        "require",
+        "ancestor-empty",
+        "node_modules/ancestor-empty/index.js",
+        "resolved",
+      ],
+      ["require", "ancestor-blocked", null, "not-found"],
+      [
+        "require",
+        "ancestor-sub/parser",
+        "node_modules/ancestor-sub/parser.js",
+        "resolved",
+      ],
     ] as const;
 
     for (const [kind, specifier, resolvedPath, status] of expectations)