refactor: per-tool MCP registry — eliminate tools[] + case-switch conflicts

__tests__/mcp-tool-registry.test.ts

@@ -0,0 +1,79 @@
+/**
+ * MCP tool registry: structural invariants.
+ *
+ * Guards against the failure mode where a future PR adds a
+ * ToolModule but forgets to implement the matching `handle<Name>`
+ * method on ToolHandler (or vice versa).
+ */
+import { describe, it, expect } from 'vitest';
+import { getToolModules, tools as registryTools } from '../src/mcp/tools/registry';
+import { ToolHandler, tools } from '../src/mcp/tools';
+
+describe('MCP tool registry — single source of truth', () => {
+  it('every tool module has a non-empty name and description', () => {
+    for (const m of getToolModules()) {
+      expect(m.definition.name).toMatch(/^codegraph_[a-z_]+$/);
+      expect(m.definition.description.length).toBeGreaterThan(20);
+    }
+  });
+
+  it('handlerKey is a string starting with "handle"', () => {
+    for (const m of getToolModules()) {
+      expect(m.handlerKey).toMatch(/^handle[A-Z][A-Za-z]+$/);
+    }
+  });
+
+  it('every registered tool has a corresponding ToolHandler method', () => {
+    const handler = new ToolHandler(null);
+    for (const m of getToolModules()) {
+      const fn = (handler as unknown as Record<string, unknown>)[m.handlerKey];
+      expect(typeof fn).toBe('function');
+    }
+  });
+
+  it('exported `tools` array exactly mirrors the registry', () => {
+    const fromRegistry = registryTools.map((t) => t.name).sort();
+    const fromExport = tools.map((t) => t.name).sort();
+    expect(fromExport).toEqual(fromRegistry);
+  });
+
+  it('all 9 main-line tools are registered (regression guard)', () => {
+    const expected = [
+      'codegraph_callees',
+      'codegraph_callers',
+      'codegraph_context',
+      'codegraph_explore',
+      'codegraph_files',
+      'codegraph_impact',
+      'codegraph_node',
+      'codegraph_search',
+      'codegraph_status',
+    ];
+    const actual = getToolModules()
+      .map((m) => m.definition.name)
+      .sort();
+    expect(actual).toEqual(expected);
+  });
+
+  it('execute() reports unknown-tool errors', async () => {
+    const handler = new ToolHandler(null);
+    const result = await handler.execute('codegraph_does_not_exist', {});
+    expect(result.isError).toBe(true);
+    expect(result.content[0]?.text).toMatch(/Unknown tool/);
+  });
+
+  it('execute() actually dispatches to the registered handler (no broken `this` binding)', async () => {
+    // No CodeGraph instance is bound, so handlers that call
+    // `getCodeGraph()` will throw — the dispatch should catch it
+    // and return an error result. The point of this test is to
+    // confirm the registry lookup + `this[handlerKey](args)` chain
+    // reaches an actual method body, not that the body succeeds.
+    const handler = new ToolHandler(null);
+    const result = await handler.execute('codegraph_status', {});
+    expect(result.isError).toBe(true);
+    // Generic tool-execution-failed envelope from execute()'s catch block.
+    expect(result.content[0]?.text).toMatch(/Tool execution failed/);
+    // Specifically because no CodeGraph was bound:
+    expect(result.content[0]?.text).toMatch(/CodeGraph not initialized/);
+  });
+});

src/mcp/index.ts

@@ -18,7 +18,8 @@
 import * as path from 'path';
 import CodeGraph, { findNearestCodeGraphRoot } from '../index';
 import { StdioTransport, JsonRpcRequest, JsonRpcNotification, ErrorCodes } from './transport';
-import { tools, ToolHandler } from './tools';
+import { ToolHandler } from './tools';
+import { getToolModule } from './tools/registry';
 
 /**
  * Convert a file:// URI to a filesystem path.
@@ -309,8 +310,9 @@ export class MCPServer {
     const toolName = params.name;
     const toolArgs = params.arguments || {};
 
-    // Validate tool exists
-    const tool = tools.find(t => t.name === toolName);
+    // Validate tool exists — O(1) Map lookup against the registry,
+    // matches the path `ToolHandler.execute()` uses internally.
+    const tool = getToolModule(toolName)?.definition;
     if (!tool) {
       this.transport.sendError(
         request.id,

src/mcp/tool-types.ts

@@ -0,0 +1,39 @@
+/**
+ * Shared MCP tool types.
+ *
+ * Lives in its own module so per-tool files in `./tools/` and
+ * the legacy class wrapper in `./tools.ts` can import the same
+ * type definitions without a circular dependency.
+ */
+
+export interface PropertySchema {
+  type: string;
+  description: string;
+  enum?: string[];
+  default?: unknown;
+}
+
+export interface ToolDefinition {
+  name: string;
+  description: string;
+  inputSchema: {
+    type: 'object';
+    properties: Record<string, PropertySchema>;
+    required?: string[];
+  };
+}
+
+export interface ToolResult {
+  content: Array<{ type: 'text'; text: string }>;
+  isError?: boolean;
+}
+
+/**
+ * Shared `projectPath` schema property — every tool's inputSchema
+ * accepts it for cross-project queries.
+ */
+export const projectPathProperty: PropertySchema = {
+  type: 'string',
+  description:
+    'Path to a different project with .codegraph/ initialized. If omitted, uses current project. Use this to query other codebases.',
+};