Resolve shared island modules by real path (#2671)

packages/runtime/src/scr_node_island_hooks.cjs

@@ -30,8 +30,19 @@ function scriptcSharedModules(nativeHost) {
   const table = JSON.parse(nativeHost.sharedTable());
   const none = { entry: (path, load) => load(null), push() {} };
   if (table.length === 0) return none;
+  const { realpathSync } = require("node:fs");
+  // Node resolves an import to the module's real path, so a module of a
+  // tree reached through a symbolic link (a cache directory under macOS's
+  // /var, which is /private/var) is keyed by its real path as well.
   const byUrl = new Map();
-  table.forEach((m, id) => byUrl.set(pathToFileURL(m.path).href, id));
+  table.forEach((m, id) => {
+    byUrl.set(pathToFileURL(m.path).href, id);
+    try {
+      byUrl.set(pathToFileURL(realpathSync(m.path)).href, id);
+    } catch {
+      // A module that is not on disk keeps only its own path.
+    }
+  });
   const TDZ = Symbol("scriptc.tdz");
   const setters = new Map(); // `${mod}:${slot}` -> [(value) => void]
   const entries = new Map(); // entry URL -> { target, late: [[mod, slot]] }

packages/runtime/src/scr_node_island_host.h

@@ -769,8 +769,19 @@ static const char scr_node_island_host_js[] =
     "  const table = JSON.parse(nativeHost.sharedTable());\012"
     "  const none = { entry: (path, load) => load(null), push() {} };\012"
     "  if (table.length === 0) return none;\012"
+    "  const { realpathSync } = require(\"node:fs\");\012"
+    "  // Node resolves an import to the module's real path, so a module of a\012"
+    "  // tree reached through a symbolic link (a cache directory under macOS's\012"
+    "  // /var, which is /private/var) is keyed by its real path as well.\012"
     "  const byUrl = new Map();\012"
-    "  table.forEach((m, id) => byUrl.set(pathToFileURL(m.path).href, id));\012"
+    "  table.forEach((m, id) => {\012"
+    "    byUrl.set(pathToFileURL(m.path).href, id);\012"
+    "    try {\012"
+    "      byUrl.set(pathToFileURL(realpathSync(m.path)).href, id);\012"
+    "    } catch {\012"
+    "      // A module that is not on disk keeps only its own path.\012"
+    "    }\012"
+    "  });\012"
     "  const TDZ = Symbol(\"scriptc.tdz\");\012"
     "  const setters = new Map(); // `${mod}:${slot}` -> [(value) => void]\012"
     "  const entries = new Map(); // entry URL -> { target, late: [[mod, slot]] }\012"

tests/harness/node-island.test.ts

@@ -18,6 +18,7 @@ import {
   realpathSync,
   rmSync,
   statSync,
+  symlinkSync,
   writeFileSync,
 } from "node:fs";
 import { tmpdir } from "node:os";
@@ -544,13 +545,18 @@ export function patchAndBump(): number {
       // Node strips types only outside node_modules, and the shared island
       // cache of these tests lives below the repository's node_modules.
       const islandCache = mkdtempSync(join(tmpdir(), "scriptc-island-cache-"));
+      // A cache reached through a symbolic link (macOS's temporary directory
+      // is under /var, which is /private/var): Node resolves the island's
+      // import to the shared module's real path.
+      const linkedCache = `${islandCache}-link`;
+      symlinkSync(islandCache, linkedCache);
       try {
-        const out = await run(join(dir, "main"), [], {
-          ...process.env,
-          XDG_CACHE_HOME: islandCache,
-        });
-        expect(out).toEqual({ stdout: "2 2\n", stderr: "", code: 0 });
+        for (const cache of [islandCache, linkedCache]) {
+          const out = await run(join(dir, "main"), [], { ...process.env, XDG_CACHE_HOME: cache });
+          expect(out).toEqual({ stdout: "2 2\n", stderr: "", code: 0 });
+        }
       } finally {
+        rmSync(linkedCache, { force: true });
         rmSync(islandCache, { recursive: true, force: true });
       }
     }, 300_000);