chore: test node_modules symlinks in npm workspace with cyclic deps (#34759)

Adds a regression spec test for the npm-workspace symlink scenario
reported in #19726.

## Background

The issue reported that an npm workspace where member packages are
symlinked into `node_modules` (as `npm install` does) caused Rust to
panic during package.json module resolution. The reproduction
(verikono/deno-npm-symlinks) has three workspace packages where `pkg-a`
and `pkg-b` import each other (a cyclic dependency).

This was fixed somewhere along the way — the maintainer noted on the
issue that it already works in v2.1.2, and I confirmed it works on
current `main` across every resolution path I tried:

- import-map resolution to the local workspace sources
- pure `node_modules` + package.json `exports` resolution
(`nodeModulesDir: manual`)
- absolute symlinks pointing outside the project root
- cyclic deps via `deno run`, `deno test` (type-check + run), and `deno
info` (which correctly canonicalizes the symlink to the real path and
shows the cycle)

## This PR

Since there was no code left to fix, this adds a regression spec test at
`tests/specs/npm/workspace_symlink_cyclic/` so the scenario doesn't
regress. The test:

- sets up an npm workspace with `main-project`, `pkg-a`, `pkg-b` (with
`pkg-a` ⇄ `pkg-b` cyclic deps), mirroring the original reproduction
- recreates the `node_modules` symlinks `npm install` produces, via a
`setup.js` step using `Deno.symlinkSync` (no symlinks committed to git)
- runs `deno test`, which resolves the symlinked workspace packages
through `node_modules` and exercises the cyclic dependency

Gated to `unix` since creating directory symlinks on Windows requires
elevated privileges.

Closes #19726

Closes denoland/divybot#440

---------

Co-authored-by: divybot <divybot@users.noreply.github.com>
Co-authored-by: Divy Srivastava <me@littledivy.com>

Author: divybot

tests/specs/npm/workspace_symlink_cyclic/__test__.jsonc

@@ -0,0 +1,20 @@
+// Regression test for https://github.com/denoland/deno/issues/19726
+//
+// An npm workspace where each member package is symlinked into the root
+// `node_modules` (as `npm install` does). `pkg-a` and `pkg-b` import each other
+// (a cyclic dependency). Resolving these symlinked workspace packages through
+// `node_modules` used to panic during package.json module resolution.
+{
+  "tempDir": true,
+  "if": "unix",
+  "steps": [
+    {
+      "args": "run -A setup.js",
+      "output": "[WILDCARD]"
+    },
+    {
+      "args": "test -A",
+      "output": "test.out"
+    }
+  ]
+}

tests/specs/npm/workspace_symlink_cyclic/deno.json

@@ -0,0 +1,10 @@
+{
+  "imports": {
+    "main-project": "./packages/main-project/src/index.ts",
+    "pkg-a": "./packages/pkg-a/src/index.ts",
+    "pkg-b": "./packages/pkg-b/src/index.ts"
+  },
+  "test": {
+    "include": ["**/src/**/*.spec.ts"]
+  }
+}

tests/specs/npm/workspace_symlink_cyclic/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "basic-npm-monorepo",
+  "version": "1.0.0",
+  "type": "module",
+  "workspaces": ["packages/*"],
+  "dependencies": {
+    "main-project": "*",
+    "pkg-a": "*",
+    "pkg-b": "*"
+  }
+}

tests/specs/npm/workspace_symlink_cyclic/packages/main-project/package.json

@@ -0,0 +1,7 @@
+{
+  "name": "main-project",
+  "version": "1.0.0",
+  "type": "module",
+  "dependencies": { "pkg-a": "*", "pkg-b": "*" },
+  "exports": { ".": "./src/index.ts" }
+}

tests/specs/npm/workspace_symlink_cyclic/packages/main-project/src/index.ts

@@ -0,0 +1,7 @@
+import { packageA } from "pkg-a";
+import { packageB } from "pkg-b";
+
+export function test() {
+  packageA();
+  packageB();
+}

tests/specs/npm/workspace_symlink_cyclic/packages/pkg-a/package.json

@@ -0,0 +1,7 @@
+{
+  "name": "pkg-a",
+  "version": "1.0.0",
+  "type": "module",
+  "dependencies": { "pkg-b": "*" },
+  "exports": { ".": "./src/index.ts" }
+}

tests/specs/npm/workspace_symlink_cyclic/packages/pkg-a/src/index.ts

@@ -0,0 +1,10 @@
+import { packageAFromPackageB } from "pkg-b";
+
+export function packageA() {
+  console.info("invoked pkg-a.packageA");
+  packageAFromPackageB();
+}
+
+export function packageBFromPackageA() {
+  console.info("invoked packageBFromPackageA");
+}

tests/specs/npm/workspace_symlink_cyclic/packages/pkg-a/src/test.spec.ts

@@ -0,0 +1,9 @@
+import { packageA } from "pkg-a";
+import { packageB } from "pkg-b";
+import { test } from "main-project";
+
+Deno.test("cyclic workspace packages resolve through node_modules symlinks", () => {
+  packageA();
+  packageB();
+  test();
+});

tests/specs/npm/workspace_symlink_cyclic/packages/pkg-b/package.json

@@ -0,0 +1,7 @@
+{
+  "name": "pkg-b",
+  "version": "1.0.0",
+  "type": "module",
+  "dependencies": { "pkg-a": "*" },
+  "exports": { ".": "./src/index.ts" }
+}

tests/specs/npm/workspace_symlink_cyclic/packages/pkg-b/src/index.ts

@@ -0,0 +1,10 @@
+import { packageBFromPackageA } from "pkg-a";
+
+export function packageB() {
+  console.info("invoked pkg-b.packageB");
+  packageBFromPackageA();
+}
+
+export function packageAFromPackageB() {
+  console.info("invoked packageAFromPackageB");
+}