test: isolate optional SDK role dependencies

scripts/check-dependency-isolation.mjs

@@ -0,0 +1,159 @@
+import { execFileSync } from "node:child_process";
+import {
+  mkdtempSync,
+  mkdirSync,
+  readFileSync,
+  rmSync,
+  writeFileSync,
+} from "node:fs";
+import { tmpdir } from "node:os";
+import { join, resolve } from "node:path";
+
+const root = resolve(import.meta.dirname, "..");
+const packageJson = JSON.parse(
+  readFileSync(join(root, "package.json"), "utf8"),
+);
+const client = "@modelcontextprotocol/client";
+const server = "@modelcontextprotocol/server";
+
+for (const role of [client, server]) {
+  if (!packageJson.peerDependencies?.[role]) {
+    throw new Error(`${role} must remain a peer dependency`);
+  }
+  if (packageJson.peerDependenciesMeta?.[role]?.optional !== true) {
+    throw new Error(`${role} must be an optional peer dependency`);
+  }
+}
+
+const temporaryRoot = mkdtempSync(join(tmpdir(), "ext-apps-role-peers-"));
+try {
+  const npmEnvironment = {
+    ...process.env,
+    npm_config_cache: join(temporaryRoot, "npm-cache"),
+  };
+  const packOutput = JSON.parse(
+    execFileSync(
+      "npm",
+      [
+        "pack",
+        "--ignore-scripts",
+        "--json",
+        "--pack-destination",
+        temporaryRoot,
+      ],
+      { cwd: root, encoding: "utf8", env: npmEnvironment },
+    ),
+  );
+  const tarball = join(temporaryRoot, packOutput[0].filename);
+
+  const consumers = [
+    {
+      name: "app-only",
+      dependencies: {
+        "@types/node": packageJson.devDependencies["@types/node"],
+        [client]: packageJson.devDependencies[client],
+        "@modelcontextprotocol/ext-apps": `file:${tarball}`,
+      },
+      absent: server,
+      entry:
+        'import { App } from "@modelcontextprotocol/ext-apps"; import { AppBridge } from "@modelcontextprotocol/ext-apps/app-bridge"; console.log(App, AppBridge);',
+    },
+    {
+      name: "server-only",
+      dependencies: {
+        "@types/node": packageJson.devDependencies["@types/node"],
+        "@modelcontextprotocol/ext-apps": `file:${tarball}`,
+        [server]: packageJson.devDependencies[server],
+      },
+      absent: client,
+      entry:
+        'import { registerAppTool } from "@modelcontextprotocol/ext-apps/server"; console.log(registerAppTool);',
+    },
+  ];
+
+  for (const consumer of consumers) {
+    const directory = join(temporaryRoot, consumer.name);
+    mkdirSync(directory);
+    writeFileSync(
+      join(directory, "package.json"),
+      JSON.stringify({
+        private: true,
+        type: "module",
+        dependencies: consumer.dependencies,
+      }),
+    );
+    execFileSync(
+      "npm",
+      [
+        "install",
+        "--ignore-scripts",
+        "--package-lock=false",
+        "--no-audit",
+        "--no-fund",
+      ],
+      { cwd: directory, stdio: "pipe", env: npmEnvironment },
+    );
+
+    const absentPath = join(
+      directory,
+      "node_modules",
+      ...consumer.absent.split("/"),
+      "package.json",
+    );
+    try {
+      readFileSync(absentPath);
+      throw new Error(
+        `${consumer.name} unexpectedly installed ${consumer.absent}`,
+      );
+    } catch (error) {
+      if (error?.code !== "ENOENT") throw error;
+    }
+
+    writeFileSync(join(directory, "entry.ts"), consumer.entry);
+    writeFileSync(
+      join(directory, "tsconfig.json"),
+      JSON.stringify({
+        compilerOptions: {
+          lib: ["ES2020", "DOM"],
+          module: "ESNext",
+          moduleResolution: "bundler",
+          noEmit: true,
+          skipLibCheck: false,
+          strict: true,
+          target: "ES2020",
+        },
+        include: ["entry.ts"],
+      }),
+    );
+    execFileSync(
+      process.execPath,
+      [join(root, "node_modules", "typescript", "bin", "tsc")],
+      { cwd: directory, stdio: "inherit" },
+    );
+
+    const metafile = join(directory, "bundle-meta.json");
+    execFileSync(
+      join(root, "node_modules", ".bin", "esbuild"),
+      [
+        "entry.ts",
+        "--bundle",
+        "--platform=browser",
+        "--outfile=bundle.js",
+        `--metafile=${metafile}`,
+      ],
+      { cwd: directory, stdio: "pipe" },
+    );
+    const bundleInputs = Object.keys(
+      JSON.parse(readFileSync(metafile, "utf8")).inputs,
+    ).join("\n");
+    if (bundleInputs.includes(`/node_modules/${consumer.absent}/`)) {
+      throw new Error(
+        `${consumer.name} unexpectedly bundled ${consumer.absent}`,
+      );
+    }
+  }
+} finally {
+  rmSync(temporaryRoot, { recursive: true, force: true });
+}
+
+console.log("Role peer dependency isolation checks passed.");