refactor(@angular/cli): add MCP test support for custom code examples

The experimental MCP server now supports an additional environment variable
for test purposes that allows custom markdown code examples to be used
with the `find_examples` tool. This uses the `NG_MCP_EXAMPLES_DIR` environment
variable.

Author: clydin

packages/angular/cli/src/commands/mcp/mcp-server.ts

@@ -74,7 +74,7 @@ export async function createMcpServer(
           ' Registration of this tool has been skipped.',
       );
     } else {
-      registerFindExampleTool(server, path.join(__dirname, '../../../lib/code-examples.db'));
+      await registerFindExampleTool(server, path.join(__dirname, '../../../lib/code-examples.db'));
     }
   }
 

packages/angular/cli/src/commands/mcp/tools/examples.ts

@@ -7,6 +7,8 @@
  */
 
 import type { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
+import { glob, readFile } from 'node:fs/promises';
+import path from 'node:path';
 import { z } from 'zod';
 
 /**
@@ -18,10 +20,20 @@ import { z } from 'zod';
  * @param server The MCP server instance.
  * @param exampleDatabasePath The path to the SQLite database file containing the examples.
  */
-export function registerFindExampleTool(server: McpServer, exampleDatabasePath: string): void {
+export async function registerFindExampleTool(
+  server: McpServer,
+  exampleDatabasePath: string,
+): Promise<void> {
   let db: import('node:sqlite').DatabaseSync | undefined;
   let queryStatement: import('node:sqlite').StatementSync | undefined;
 
+  // Runtime directory of examples uses an in-memory database
+  if (process.env['NG_MCP_EXAMPLES_DIR']) {
+    db = await setupRuntimeExamples(process.env['NG_MCP_EXAMPLES_DIR']);
+  }
+
+  suppressSqliteWarning();
+
   server.registerTool(
     'find_examples',
     {
@@ -67,11 +79,11 @@ Examples of queries:
       },
     },
     async ({ query }) => {
-      if (!db || !queryStatement) {
-        suppressSqliteWarning();
-
+      if (!db) {
         const { DatabaseSync } = await import('node:sqlite');
         db = new DatabaseSync(exampleDatabasePath, { readOnly: true });
+      }
+      if (!queryStatement) {
         queryStatement = db.prepare('SELECT * from examples WHERE examples MATCH ? ORDER BY rank;');
       }
 
@@ -172,3 +184,27 @@ function suppressSqliteWarning() {
     return originalProcessEmit.apply(process, arguments as any);
   };
 }
+
+async function setupRuntimeExamples(
+  examplesPath: string,
+): Promise<import('node:sqlite').DatabaseSync> {
+  const { DatabaseSync } = await import('node:sqlite');
+  const db = new DatabaseSync(':memory:');
+
+  db.exec(`CREATE VIRTUAL TABLE examples USING fts5(content, tokenize = 'porter ascii');`);
+
+  const insertStatement = db.prepare('INSERT INTO examples(content) VALUES(?);');
+
+  db.exec('BEGIN TRANSACTION');
+  for await (const entry of glob('*.md', { cwd: examplesPath, withFileTypes: true })) {
+    if (!entry.isFile()) {
+      continue;
+    }
+
+    const example = await readFile(path.join(entry.parentPath, entry.name), 'utf-8');
+    insertStatement.run(example);
+  }
+  db.exec('END TRANSACTION');
+
+  return db;
+}