feat(mcp): add package-backed ast-grep MCP

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent) Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
2026-05-18 21:19:15 +09:00
parent 4ea29e2c94
commit 499aff011a
19 changed files with 1372 additions and 0 deletions
@@ -0,0 +1,170 @@
+import { afterEach, describe, expect, it } from "bun:test";
+import { mkdirSync, mkdtempSync, realpathSync, rmSync, symlinkSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { handleAstGrepMcpRequest } from "./mcp";
+import type { RunOptions } from "./runner";
+import type { SgResult } from "./types";
+
+const emptyResult: SgResult = {
+  matches: [],
+  totalMatches: 0,
+  truncated: false,
+};
+
+const temporaryDirectories: string[] = [];
+
+function createTemporaryDirectory(prefix: string): string {
+  const directory = mkdtempSync(join(tmpdir(), prefix));
+  temporaryDirectories.push(directory);
+  return directory;
+}
+
+afterEach(() => {
+  for (const directory of temporaryDirectories.splice(0)) {
+    rmSync(directory, { recursive: true, force: true });
+  }
+});
+
+describe("ast-grep MCP", () => {
+  it("#given initialize request #when handled #then advertises tools capability", async () => {
+    const response = await handleAstGrepMcpRequest({
+      jsonrpc: "2.0",
+      id: 1,
+      method: "initialize",
+      params: { protocolVersion: "2024-11-05" },
+    });
+
+    expect(response).toEqual({
+      jsonrpc: "2.0",
+      id: 1,
+      result: {
+        capabilities: { tools: { listChanged: false } },
+        serverInfo: { name: "ast_grep", version: "0.1.0" },
+        protocolVersion: "2024-11-05",
+      },
+    });
+  });
+
+  it("#given tools list request #when handled #then exposes search and replace tools", async () => {
+    const response = await handleAstGrepMcpRequest({ jsonrpc: "2.0", id: "tools", method: "tools/list" });
+
+    expect(response?.result?.tools?.map((tool) => tool.name)).toEqual(["search", "replace"]);
+  });
+
+  it("#given search call without paths #when handled #then defaults paths to workspace directory", async () => {
+    const captured: { value?: RunOptions } = {};
+    const workspaceDirectory = createTemporaryDirectory("omo-ast-grep-workspace-");
+    const response = await handleAstGrepMcpRequest(
+      {
+        jsonrpc: "2.0",
+        id: "search",
+        method: "tools/call",
+        params: { name: "search", arguments: { pattern: "console.log($$$)", lang: "typescript" } },
+      },
+      {
+        workspaceDirectory,
+        runSg: async (options) => {
+          captured.value = options;
+          return emptyResult;
+        },
+      },
+    );
+
+    expect(captured.value).toEqual({ pattern: "console.log($$$)", lang: "typescript", cwd: realpathSync(workspaceDirectory), paths: ["."], globs: undefined, context: undefined });
+    expect(response?.result?.content?.[0]?.text).toContain("No matches found");
+  });
+
+  it("#given replace call without dryRun #when handled #then keeps dry-run default", async () => {
+    const captured: { value?: RunOptions } = {};
+    const workspaceDirectory = createTemporaryDirectory("omo-ast-grep-replace-workspace-");
+    mkdirSync(join(workspaceDirectory, "src"));
+    await handleAstGrepMcpRequest(
+      {
+        jsonrpc: "2.0",
+        id: "replace",
+        method: "tools/call",
+        params: {
+          name: "replace",
+          arguments: { pattern: "console.log($MSG)", rewrite: "logger.info($MSG)", lang: "typescript", paths: ["src"] },
+        },
+      },
+      {
+        workspaceDirectory,
+        runSg: async (options) => {
+          captured.value = options;
+          return emptyResult;
+        },
+      },
+    );
+
+    expect(captured.value).toEqual({
+      pattern: "console.log($MSG)",
+      rewrite: "logger.info($MSG)",
+      lang: "typescript",
+      cwd: realpathSync(workspaceDirectory),
+      paths: ["src"],
+      globs: undefined,
+      updateAll: false,
+    });
+  });
+
+  it("#given disabled replace tool #when listed and called #then hides and rejects it", async () => {
+    const listResponse = await handleAstGrepMcpRequest({ jsonrpc: "2.0", id: "tools", method: "tools/list" }, { disabledTools: ["replace"] });
+
+    expect(listResponse?.result?.tools?.map((tool) => tool.name)).toEqual(["search"]);
+
+    const callResponse = await handleAstGrepMcpRequest(
+      {
+        jsonrpc: "2.0",
+        id: "replace",
+        method: "tools/call",
+        params: {
+          name: "replace",
+          arguments: { pattern: "console.log($MSG)", rewrite: "logger.info($MSG)", lang: "typescript", paths: ["src"] },
+        },
+      },
+      { disabledTools: ["replace"] },
+    );
+
+    expect(callResponse?.result?.isError).toBe(true);
+    expect(callResponse?.result?.content?.[0]?.text).toContain("ast-grep tool is disabled: replace");
+  });
+
+  it("#given unsafe paths #when search is called #then rejects before running ast-grep", async () => {
+    const workspaceDirectory = createTemporaryDirectory("omo-ast-grep-sandbox-");
+    const outsideDirectory = createTemporaryDirectory("omo-ast-grep-outside-");
+    symlinkSync(outsideDirectory, join(workspaceDirectory, "outside-link"));
+    let didRun = false;
+
+    for (const path of ["../outside", "/tmp", "--update-all", "outside-link"]) {
+      const response = await handleAstGrepMcpRequest(
+        {
+          jsonrpc: "2.0",
+          id: path,
+          method: "tools/call",
+          params: { name: "search", arguments: { pattern: "console.log($$$)", lang: "typescript", paths: [path] } },
+        },
+        {
+          workspaceDirectory,
+          runSg: async () => {
+            didRun = true;
+            return emptyResult;
+          },
+        },
+      );
+
+      expect(response?.result?.isError).toBe(true);
+    }
+
+    expect(didRun).toBe(false);
+  });
+
+  it("#given tools list request #when handled #then preserves detailed ast-grep guidance", async () => {
+    const response = await handleAstGrepMcpRequest({ jsonrpc: "2.0", id: "tools", method: "tools/list" });
+    const searchTool = response?.result?.tools?.find((tool) => tool.name === "search");
+
+    expect(searchTool?.description).toContain("This is NOT regex");
+    expect(searchTool?.description).toContain("Meta-variables");
+  });
+});