refactor(client,server): move stdio transports to ./stdio subpath export (#1871)

Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>

packages/client/test/client/barrelClean.test.ts

@@ -0,0 +1,55 @@
+import { execFileSync } from 'node:child_process';
+import { existsSync, readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+import { beforeAll, describe, expect, test } from 'vitest';
+
+const pkgDir = join(dirname(fileURLToPath(import.meta.url)), '../..');
+const distDir = join(pkgDir, 'dist');
+const NODE_ONLY = /\b(child_process|cross-spawn|node:stream|node:child_process)\b/;
+
+function chunkImportsOf(entryPath: string): string[] {
+    const visited = new Set<string>();
+    const queue = [entryPath];
+    while (queue.length > 0) {
+        const file = queue.shift()!;
+        if (visited.has(file)) continue;
+        visited.add(file);
+        const src = readFileSync(file, 'utf8');
+        for (const m of src.matchAll(/from\s+["']\.\/(.+?\.mjs)["']/g)) {
+            queue.push(join(dirname(file), m[1]!));
+        }
+    }
+    visited.delete(entryPath);
+    return [...visited];
+}
+
+describe('@modelcontextprotocol/client root entry is browser-safe', () => {
+    beforeAll(() => {
+        if (!existsSync(join(distDir, 'index.mjs')) || !existsSync(join(distDir, 'stdio.mjs'))) {
+            execFileSync('pnpm', ['build'], { cwd: pkgDir, stdio: 'inherit' });
+        }
+    }, 60_000);
+
+    test('dist/index.mjs contains no process-spawning runtime imports', () => {
+        const entry = join(distDir, 'index.mjs');
+        expect(readFileSync(entry, 'utf8')).not.toMatch(NODE_ONLY);
+    });
+
+    test('chunks transitively imported by dist/index.mjs contain no process-spawning runtime imports', () => {
+        const entry = join(distDir, 'index.mjs');
+        for (const chunk of chunkImportsOf(entry)) {
+            expect({ chunk, content: readFileSync(chunk, 'utf8') }).not.toEqual(
+                expect.objectContaining({ content: expect.stringMatching(NODE_ONLY) })
+            );
+        }
+    });
+
+    test('dist/stdio.mjs exists and exports StdioClientTransport', () => {
+        const stdio = readFileSync(join(distDir, 'stdio.mjs'), 'utf8');
+        expect(stdio).toMatch(/\bStdioClientTransport\b/);
+        expect(stdio).toMatch(/\bgetDefaultEnvironment\b/);
+        expect(stdio).toMatch(/\bDEFAULT_INHERITED_ENV_VARS\b/);
+    });
+});