[compiler] Add a basic mcp tool

Adds the ability to compile as a tool

compiler/packages/react-compiler-mcp-server/package.json

@@ -11,7 +11,13 @@
     "watch": "yarn build --watch"
   },
   "dependencies": {
-    "@modelcontextprotocol/sdk": "^1.9.0"
+    "@babel/core": "^7.26.0",
+    "@babel/parser": "^7.26",
+    "@babel/plugin-syntax-typescript": "^7.25.9",
+    "@babel/types": "^7.26.0",
+    "@modelcontextprotocol/sdk": "^1.9.0",
+    "prettier": "^3.3.3",
+    "zod": "^3.23.8"
   },
   "devDependencies": {},
   "license": "MIT",

compiler/packages/react-compiler-mcp-server/src/compiler/index.ts

@@ -0,0 +1,66 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import type * as BabelCore from '@babel/core';
+import {parseAsync, transformFromAstAsync} from '@babel/core';
+import BabelPluginReactCompiler, {
+  type PluginOptions,
+} from 'babel-plugin-react-compiler/src';
+import * as babelParser from 'prettier/plugins/babel.js';
+import estreeParser from 'prettier/plugins/estree';
+import * as typescriptParser from 'prettier/plugins/typescript';
+import * as prettier from 'prettier/standalone';
+
+export let lastResult: BabelCore.BabelFileResult | null = null;
+
+type CompileOptions = {
+  text: string;
+  file: string;
+  options: Partial<PluginOptions> | null;
+};
+export async function compile({
+  text,
+  file,
+  options,
+}: CompileOptions): Promise<BabelCore.BabelFileResult> {
+  const ast = await parseAsync(text, {
+    sourceFileName: file,
+    parserOpts: {
+      plugins: ['typescript', 'jsx'],
+    },
+    sourceType: 'module',
+  });
+  if (ast == null) {
+    throw new Error('Could not parse');
+  }
+  const plugins =
+    options != null
+      ? [[BabelPluginReactCompiler, options]]
+      : [[BabelPluginReactCompiler]];
+  const result = await transformFromAstAsync(ast, text, {
+    filename: file,
+    highlightCode: false,
+    retainLines: true,
+    plugins,
+    sourceType: 'module',
+    sourceFileName: file,
+  });
+  if (result?.code == null) {
+    throw new Error(
+      `Expected BabelPluginReactCompiler to compile successfully, got ${result}`,
+    );
+  }
+  result.code = await prettier.format(result.code, {
+    semi: false,
+    parser: 'babel-ts',
+    plugins: [babelParser, estreeParser, typescriptParser],
+  });
+  if (result.code != null) {
+    lastResult = result;
+  }
+  return result;
+}

compiler/packages/react-compiler-mcp-server/src/index.ts

@@ -7,6 +7,24 @@
 
 import {McpServer} from '@modelcontextprotocol/sdk/server/mcp.js';
 import {StdioServerTransport} from '@modelcontextprotocol/sdk/server/stdio.js';
+import {z} from 'zod';
+import {compile} from './compiler';
+import {
+  CompilerPipelineValue,
+  printReactiveFunctionWithOutlined,
+  printFunctionWithOutlined,
+} from 'babel-plugin-react-compiler/src';
+import {type CallToolResult} from '@modelcontextprotocol/sdk/types.js';
+
+export type PrintedCompilerPipelineValue =
+  | {
+      kind: 'hir';
+      name: string;
+      fnName: string | null;
+      value: string;
+    }
+  | {kind: 'reactive'; name: string; fnName: string | null; value: string}
+  | {kind: 'debug'; name: string; fnName: string | null; value: string};
 
 const server = new McpServer({
   name: 'React Compiler',
@@ -17,6 +35,110 @@ const server = new McpServer({
   },
 });
 
+server.tool(
+  'analyze',
+  'Use React Compiler to analyze React code',
+  {
+    text: z.string(),
+    passName: z.string().optional(),
+  },
+  async ({text, passName}) => {
+    const pipelinePasses = new Map<
+      string,
+      Array<PrintedCompilerPipelineValue>
+    >();
+    const recordPass: (
+      result: PrintedCompilerPipelineValue,
+    ) => void = result => {
+      const entry = pipelinePasses.get(result.name);
+      if (Array.isArray(entry)) {
+        entry.push(result);
+      } else {
+        pipelinePasses.set(result.name, [result]);
+      }
+    };
+    const logIR = (result: CompilerPipelineValue): void => {
+      switch (result.kind) {
+        case 'ast': {
+          break;
+        }
+        case 'hir': {
+          recordPass({
+            kind: 'hir',
+            fnName: result.value.id,
+            name: result.name,
+            value: printFunctionWithOutlined(result.value),
+          });
+          break;
+        }
+        case 'reactive': {
+          recordPass({
+            kind: 'reactive',
+            fnName: result.value.id,
+            name: result.name,
+            value: printReactiveFunctionWithOutlined(result.value),
+          });
+          break;
+        }
+        case 'debug': {
+          recordPass({
+            kind: 'debug',
+            fnName: null,
+            name: result.name,
+            value: result.value,
+          });
+          break;
+        }
+        default: {
+          const _: never = result;
+          throw new Error(`Unhandled result ${result}`);
+        }
+      }
+    };
+    const compilerOptions = {
+      logger: {
+        debugLogIRs: logIR,
+        logEvent: () => {},
+      },
+    };
+    try {
+      const result = await compile({
+        text,
+        file: 'anonymous.tsx',
+        options: compilerOptions,
+      });
+      if (result.code == null) {
+        return {
+          isError: true,
+          content: [{type: 'text', text: 'Error: Could not compile'}],
+        };
+      }
+      const requestedPasses: Array<{type: 'text'; text: string}> = [];
+      if (passName != null) {
+        const requestedPass = pipelinePasses.get(passName);
+        if (requestedPass !== undefined) {
+          for (const pipelineValue of requestedPass) {
+            if (pipelineValue.name === passName) {
+              requestedPasses.push({
+                type: 'text',
+                text: pipelineValue.value,
+              });
+            }
+          }
+        }
+      }
+      return {
+        content: [{type: 'text', text: result.code}, ...requestedPasses],
+      };
+    } catch (err) {
+      return {
+        isError: true,
+        content: [{type: 'text', text: `Error: ${err}`}],
+      };
+    }
+  },
+);
+
 async function main() {
   const transport = new StdioServerTransport();
   await server.connect(transport);

compiler/yarn.lock

@@ -63,6 +63,11 @@
   resolved "https://registry.yarnpkg.com/@babel/compat-data/-/compat-data-7.26.3.tgz#99488264a56b2aded63983abd6a417f03b92ed02"
   integrity sha512-nHIxvKPniQXpmQLb0vhY3VaFb3S0YrTAwpOWJZh1wn3oJPjJk9Asva204PsBdmAE8vpzfHudT8DB0scYvy9q0g==
 
+"@babel/compat-data@^7.26.8":
+  version "7.26.8"
+  resolved "https://registry.yarnpkg.com/@babel/compat-data/-/compat-data-7.26.8.tgz#821c1d35641c355284d4a870b8a4a7b0c141e367"
+  integrity sha512-oH5UPLMWR3L2wEFLnFJ1TZXqHufiTKAiLfqw5zkhS4dKXLJ10yVztfil/twG8EDTA4F/tvVNw9nOl4ZMslB8rQ==
+
 "@babel/core@^7.0.0", "@babel/core@^7.2.0":
   version "7.2.0"
   resolved "https://registry.yarnpkg.com/@babel/core/-/core-7.2.0.tgz#a4dd3814901998e93340f0086e9867fefa163ada"
@@ -104,6 +109,27 @@
     json5 "^2.2.3"
     semver "^6.3.1"
 
+"@babel/core@^7.26.0":
+  version "7.26.10"
+  resolved "https://registry.yarnpkg.com/@babel/core/-/core-7.26.10.tgz#5c876f83c8c4dcb233ee4b670c0606f2ac3000f9"
+  integrity sha512-vMqyb7XCDMPvJFFOaT9kxtiRh42GwlZEg1/uIgtZshS5a/8OaduUfCi7kynKgc3Tw/6Uo2D+db9qBttghhmxwQ==
+  dependencies:
+    "@ampproject/remapping" "^2.2.0"
+    "@babel/code-frame" "^7.26.2"
+    "@babel/generator" "^7.26.10"
+    "@babel/helper-compilation-targets" "^7.26.5"
+    "@babel/helper-module-transforms" "^7.26.0"
+    "@babel/helpers" "^7.26.10"
+    "@babel/parser" "^7.26.10"
+    "@babel/template" "^7.26.9"
+    "@babel/traverse" "^7.26.10"
+    "@babel/types" "^7.26.10"
+    convert-source-map "^2.0.0"
+    debug "^4.1.0"
+    gensync "^1.0.0-beta.2"
+    json5 "^2.2.3"
+    semver "^6.3.1"
+
 "@babel/generator@7.2.0", "@babel/generator@^7.0.0", "@babel/generator@^7.2.0":
   version "7.2.0"
   resolved "https://registry.yarnpkg.com/@babel/generator/-/generator-7.2.0.tgz#eaf3821fa0301d9d4aef88e63d4bcc19b73ba16c"
@@ -137,6 +163,17 @@
     "@jridgewell/trace-mapping" "^0.3.25"
     jsesc "^3.0.2"
 
+"@babel/generator@^7.27.0":
+  version "7.27.0"
+  resolved "https://registry.yarnpkg.com/@babel/generator/-/generator-7.27.0.tgz#764382b5392e5b9aff93cadb190d0745866cbc2c"
+  integrity sha512-VybsKvpiN1gU1sdMZIp7FcqphVVKEwcuj02x73uvcHE0PTihx1nlBcowYWhDwjpoAXRv43+gDzyggGnn1XZhVw==
+  dependencies:
+    "@babel/parser" "^7.27.0"
+    "@babel/types" "^7.27.0"
+    "@jridgewell/gen-mapping" "^0.3.5"
+    "@jridgewell/trace-mapping" "^0.3.25"
+    jsesc "^3.0.2"
+
 "@babel/helper-annotate-as-pure@^7.18.6":
   version "7.18.6"
   resolved "https://registry.yarnpkg.com/@babel/helper-annotate-as-pure/-/helper-annotate-as-pure-7.18.6.tgz#eaa49f6f80d5a33f9a5dd2276e6d6e451be0a6bb"
@@ -187,6 +224,17 @@
     lru-cache "^5.1.1"
     semver "^6.3.1"
 
+"@babel/helper-compilation-targets@^7.26.5":
+  version "7.27.0"
+  resolved "https://registry.yarnpkg.com/@babel/helper-compilation-targets/-/helper-compilation-targets-7.27.0.tgz#de0c753b1cd1d9ab55d473c5a5cf7170f0a81880"
+  integrity sha512-LVk7fbXml0H2xH34dFzKQ7TDZ2G4/rVTOrq9V+icbbadjbVxxeFeDsNHv2SrZeWoA+6ZiTyWYWtScEIW07EAcA==
+  dependencies:
+    "@babel/compat-data" "^7.26.8"
+    "@babel/helper-validator-option" "^7.25.9"
+    browserslist "^4.24.0"
+    lru-cache "^5.1.1"
+    semver "^6.3.1"
+
 "@babel/helper-create-class-features-plugin@^7.18.6":
   version "7.22.9"
   resolved "https://registry.yarnpkg.com/@babel/helper-create-class-features-plugin/-/helper-create-class-features-plugin-7.22.9.tgz#c36ea240bb3348f942f08b0fbe28d6d979fab236"
@@ -629,6 +677,14 @@
     "@babel/template" "^7.25.9"
     "@babel/types" "^7.26.0"
 
+"@babel/helpers@^7.26.10":
+  version "7.27.0"
+  resolved "https://registry.yarnpkg.com/@babel/helpers/-/helpers-7.27.0.tgz#53d156098defa8243eab0f32fa17589075a1b808"
+  integrity sha512-U5eyP/CTFPuNE3qk+WZMxFkp/4zUzdceQlfzf7DdGdhp+Fezd7HD+i8Y24ZuTMKX3wQBld449jijbGq6OdGNQg==
+  dependencies:
+    "@babel/template" "^7.27.0"
+    "@babel/types" "^7.27.0"
+
 "@babel/highlight@^7.18.6":
   version "7.18.6"
   resolved "https://registry.yarnpkg.com/@babel/highlight/-/highlight-7.18.6.tgz#81158601e93e2563795adcbfbdf5d64be3f2ecdf"
@@ -667,7 +723,7 @@
   resolved "https://registry.yarnpkg.com/@babel/parser/-/parser-7.19.3.tgz#8dd36d17c53ff347f9e55c328710321b49479a9a"
   integrity sha512-pJ9xOlNWHiy9+FuFP09DEAFbAn4JskgRsVcc169w2xRBC3FRGuQEwjeIMMND9L2zc0iEhO/tGv4Zq+km+hxNpQ==
 
-"@babel/parser@^7.20.15":
+"@babel/parser@^7.20.15", "@babel/parser@^7.26", "@babel/parser@^7.27.0":
   version "7.27.0"
   resolved "https://registry.yarnpkg.com/@babel/parser/-/parser-7.27.0.tgz#3d7d6ee268e41d2600091cbd4e145ffee85a44ec"
   integrity sha512-iaepho73/2Pz7w2eMS0Q5f83+0RKI7i4xmiYeBmDzfRVbQtTOG7Ts0S4HzJVsTMGI9keU8rNfuZr8DKfSt7Yyg==
@@ -1653,6 +1709,15 @@
     "@babel/parser" "^7.26.9"
     "@babel/types" "^7.26.9"
 
+"@babel/template@^7.27.0":
+  version "7.27.0"
+  resolved "https://registry.yarnpkg.com/@babel/template/-/template-7.27.0.tgz#b253e5406cc1df1c57dcd18f11760c2dbf40c0b4"
+  integrity sha512-2ncevenBqXI6qRMukPlXwHKHchC7RyMuu4xv5JBXRfOGVcTy1mXCD12qrp7Jsoxll1EV3+9sE4GugBVRjT2jFA==
+  dependencies:
+    "@babel/code-frame" "^7.26.2"
+    "@babel/parser" "^7.27.0"
+    "@babel/types" "^7.27.0"
+
 "@babel/template@^7.3.3":
   version "7.18.6"
   resolved "https://registry.yarnpkg.com/@babel/template/-/template-7.18.6.tgz#1283f4993e00b929d6e2d3c72fdc9168a2977a31"
@@ -1690,6 +1755,19 @@
     debug "^4.3.1"
     globals "^11.1.0"
 
+"@babel/traverse@^7.26.10":
+  version "7.27.0"
+  resolved "https://registry.yarnpkg.com/@babel/traverse/-/traverse-7.27.0.tgz#11d7e644779e166c0442f9a07274d02cd91d4a70"
+  integrity sha512-19lYZFzYVQkkHkl4Cy4WrAVcqBkgvV2YM2TU3xG6DIwO7O3ecbDPfW3yM3bjAGcqcQHi+CCtjMR3dIEHxsd6bA==
+  dependencies:
+    "@babel/code-frame" "^7.26.2"
+    "@babel/generator" "^7.27.0"
+    "@babel/parser" "^7.27.0"
+    "@babel/template" "^7.27.0"
+    "@babel/types" "^7.27.0"
+    debug "^4.3.1"
+    globals "^11.1.0"
+
 "@babel/traverse@^7.26.5", "@babel/traverse@^7.26.9":
   version "7.26.10"
   resolved "https://registry.yarnpkg.com/@babel/traverse/-/traverse-7.26.10.tgz#43cca33d76005dbaa93024fae536cc1946a4c380"