fix(create-symlink): Generate shims for missing bin scripts for Windows

utils/create-symlink/__tests__/create-symlink.test.js

@@ -15,6 +15,8 @@ describe("create-symlink", () => {
   fs.unlink.mockResolvedValue();
   fs.symlink.mockResolvedValue();
   fs.pathExists.mockResolvedValue(true);
+  fs.outputFile.mockResolvedValue();
+  fs.remove.mockResolvedValue();
   cmdShim.mockResolvedValue();
 
   if (process.platform !== "win32") {
@@ -86,5 +88,33 @@ describe("create-symlink", () => {
       expect(fs.unlink).toHaveBeenLastCalledWith(dst);
       expect(fs.symlink).toHaveBeenLastCalledWith(src, dst, type);
     });
+
+    it("creates stub symlink to executable that doesn't exist yet", async () => {
+      const src = path.resolve("./packages/package-3/cli.js");
+      const dst = path.resolve("./packages/package-1/node_modules/.bin/package-3");
+      const type = "exec";
+
+      fs.pathExists.mockResolvedValueOnce(false);
+
+      await createSymlink(src, dst, type);
+
+      expect(fs.outputFile).toHaveBeenLastCalledWith(src, "");
+      expect(cmdShim).toHaveBeenLastCalledWith(src, dst);
+      expect(fs.remove).toHaveBeenLastCalledWith(src);
+    });
+
+    it("does not swallow cmd-shim errors when executable doesn't exist yet", async () => {
+      cmdShim.mockImplementationOnce(() => Promise.reject(new Error("oh no")));
+      fs.pathExists.mockResolvedValueOnce(false);
+
+      try {
+        await createSymlink("src", "dst", "exec");
+      } catch (err) {
+        expect(err.message).toBe("oh no");
+        expect(fs.remove).toHaveBeenLastCalledWith("src");
+      }
+
+      expect.hasAssertions();
+    });
   }
 });

utils/create-symlink/create-symlink.js

@@ -50,7 +50,26 @@ function createPosixSymlink(src, dest, _type) {
 
 function createWindowsSymlink(src, dest, type) {
   if (type === "exec") {
-    return cmdShim(src, dest);
+    // If the src exists, shim directly.
+    // If the src doesn't exist yet, create a temp src so cmd-shim doesn't explode.
+    return fs.pathExists(src).then(exists => {
+      if (exists) {
+        return cmdShim(src, dest);
+      }
+
+      return fs
+        .outputFile(src, "")
+        .then(() => cmdShim(src, dest))
+        .then(
+          // fs.remove() never rejects
+          () => fs.remove(src),
+          err =>
+            fs.remove(src).then(() => {
+              // clean up, but don't swallow error
+              throw err;
+            })
+        );
+    });
   }
 
   return createSymbolicLink(src, dest, type);