Add --analyze flag to enable bundle analyzer to CLI

packages/snaps-cli/package.json

@@ -112,6 +112,7 @@
     "util": "^0.12.5",
     "vm-browserify": "^1.1.2",
     "webpack": "^5.88.0",
+    "webpack-bundle-analyzer": "^4.10.2",
     "webpack-merge": "^5.9.0",
     "yargs": "^17.7.1"
   },

packages/snaps-cli/src/builders.ts

@@ -6,8 +6,12 @@ export enum TranspilationModes {
   None = 'none',
 }
 
-const builders: Record<string, Readonly<Options>> = {
-  // eslint-disable-next-line @typescript-eslint/naming-convention
+const builders = {
+  analyze: {
+    describe: 'Analyze the Snap bundle',
+    type: 'boolean',
+  },
+
   config: {
     alias: 'c',
     describe: 'Path to config file',
@@ -146,6 +150,6 @@ const builders: Record<string, Readonly<Options>> = {
     type: 'boolean',
     deprecated: true,
   },
-};
+} as const satisfies Record<string, Readonly<Options>>;
 
 export default builders;

packages/snaps-cli/src/commands/build/build.test.ts

@@ -1,5 +1,7 @@
 import { DEFAULT_SNAP_BUNDLE } from '@metamask/snaps-utils/test-utils';
 import fs from 'fs';
+import type { Compiler } from 'webpack';
+import { BundleAnalyzerPlugin } from 'webpack-bundle-analyzer';
 
 import { getMockConfig } from '../../test-utils';
 import { evaluate } from '../eval';
@@ -10,6 +12,10 @@ jest.mock('fs');
 jest.mock('../eval');
 jest.mock('./implementation');
 
+jest.mock('webpack-bundle-analyzer', () => ({
+  BundleAnalyzerPlugin: jest.fn(),
+}));
+
 describe('buildHandler', () => {
   it('builds a snap', async () => {
     await fs.promises.writeFile('/input.js', DEFAULT_SNAP_BUNDLE);
@@ -27,6 +33,7 @@ describe('buildHandler', () => {
 
     expect(process.exitCode).not.toBe(1);
     expect(build).toHaveBeenCalledWith(config, {
+      analyze: false,
       evaluate: false,
       spinner: expect.any(Object),
     });
@@ -36,7 +43,54 @@ describe('buildHandler', () => {
     );
   });
 
-  it('does note evaluate if the evaluate option is set to false', async () => {
+  it('analyzes a snap bundle', async () => {
+    await fs.promises.writeFile('/input.js', DEFAULT_SNAP_BUNDLE);
+
+    jest.spyOn(console, 'log').mockImplementation();
+    const config = getMockConfig('webpack', {
+      input: '/input.js',
+      output: {
+        path: '/foo',
+        filename: 'output.js',
+      },
+    });
+
+    const compiler: Compiler = {
+      // @ts-expect-error: Mock `Compiler` object.
+      options: {
+        plugins: [new BundleAnalyzerPlugin()],
+      },
+    };
+
+    const plugin = jest.mocked(BundleAnalyzerPlugin);
+    const instance = plugin.mock.instances[0];
+
+    // @ts-expect-error: Partial `server` mock.
+    instance.server = Promise.resolve({
+      http: {
+        address: () => 'http://localhost:8888',
+      },
+    });
+
+    jest.mocked(build).mockResolvedValueOnce(compiler);
+
+    await buildHandler(config, true);
+
+    expect(process.exitCode).not.toBe(1);
+    expect(build).toHaveBeenCalledWith(config, {
+      analyze: true,
+      evaluate: false,
+      spinner: expect.any(Object),
+    });
+
+    expect(console.log).toHaveBeenCalledWith(
+      expect.stringContaining(
+        'Bundle analyzer running at http://localhost:8888.',
+      ),
+    );
+  });
+
+  it('does not evaluate if the evaluate option is set to false', async () => {
     await fs.promises.writeFile('/input.js', DEFAULT_SNAP_BUNDLE);
 
     jest.spyOn(console, 'log').mockImplementation();

packages/snaps-cli/src/commands/build/build.ts

@@ -1,15 +1,19 @@
 import { isFile } from '@metamask/snaps-utils/node';
+import { assert } from '@metamask/utils';
 import { resolve as pathResolve } from 'path';
 
 import type { ProcessedConfig, ProcessedWebpackConfig } from '../../config';
 import { CommandError } from '../../errors';
 import type { Steps } from '../../utils';
-import { executeSteps, info } from '../../utils';
+import { success, executeSteps, info } from '../../utils';
 import { evaluate } from '../eval';
 import { build } from './implementation';
+import { getBundleAnalyzerPort } from './utils';
 
 type BuildContext = {
+  analyze: boolean;
   config: ProcessedWebpackConfig;
+  port?: number;
 };
 
 const steps: Steps<BuildContext> = [
@@ -27,10 +31,25 @@ const steps: Steps<BuildContext> = [
   },
   {
     name: 'Building the snap bundle.',
-    task: async ({ config, spinner }) => {
+    task: async ({ analyze, config, spinner }) => {
       // We don't evaluate the bundle here, because it's done in a separate
       // step.
-      return await build(config, { evaluate: false, spinner });
+      const compiler = await build(config, {
+        analyze,
+        evaluate: false,
+        spinner,
+      });
+
+      if (analyze) {
+        return {
+          analyze,
+          config,
+          spinner,
+          port: await getBundleAnalyzerPort(compiler),
+        };
+      }
+
+      return undefined;
     },
   },
   {
@@ -48,6 +67,16 @@ const steps: Steps<BuildContext> = [
       info(`Snap bundle evaluated successfully.`, spinner);
     },
   },
+  {
+    name: 'Running analyser.',
+    condition: ({ analyze }) => analyze,
+    task: async ({ spinner, port }) => {
+      assert(port, 'Port is not defined.');
+      success(`Bundle analyzer running at http://localhost:${port}.`, spinner);
+
+      spinner.stop();
+    },
+  },
 ] as const;
 
 /**
@@ -57,10 +86,15 @@ const steps: Steps<BuildContext> = [
  * This creates the destination directory if it doesn't exist.
  *
  * @param config - The config object.
+ * @param analyze - Whether to analyze the bundle.
  * @returns Nothing.
  */
-export async function buildHandler(config: ProcessedConfig): Promise<void> {
+export async function buildHandler(
+  config: ProcessedConfig,
+  analyze = false,
+): Promise<void> {
   return await executeSteps(steps, {
     config,
+    analyze,
   });
 }

packages/snaps-cli/src/commands/build/implementation.ts

@@ -1,3 +1,5 @@
+import type { Compiler } from 'webpack';
+
 import type { ProcessedWebpackConfig } from '../../config';
 import type { WebpackOptions } from '../../webpack';
 import { getCompiler } from '../../webpack';
@@ -14,7 +16,7 @@ export async function build(
   options?: WebpackOptions,
 ) {
   const compiler = await getCompiler(config, options);
-  return await new Promise<void>((resolve, reject) => {
+  return await new Promise<Compiler>((resolve, reject) => {
     compiler.run((runError) => {
       if (runError) {
         reject(runError);
@@ -27,7 +29,7 @@ export async function build(
           return;
         }
 
-        resolve();
+        resolve(compiler);
       });
     });
   });

packages/snaps-cli/src/commands/build/index.test.ts

@@ -10,8 +10,8 @@ describe('build command', () => {
     const config = getMockConfig('webpack');
 
     // @ts-expect-error - Partial `YargsArgs` is fine for testing.
-    await command.handler({ context: { config } });
+    await command.handler({ analyze: false, context: { config } });
 
-    expect(buildHandler).toHaveBeenCalledWith(config);
+    expect(buildHandler).toHaveBeenCalledWith(config, false);
   });
 });

packages/snaps-cli/src/commands/build/index.ts

@@ -9,6 +9,7 @@ const command = {
   desc: 'Build snap from source',
   builder: (yarg: yargs.Argv) => {
     yarg
+      .option('analyze', builders.analyze)
       .option('dist', builders.dist)
       .option('eval', builders.eval)
       .option('manifest', builders.manifest)
@@ -22,7 +23,8 @@ const command = {
       .implies('writeManifest', 'manifest')
       .implies('depsToTranspile', 'transpilationMode');
   },
-  handler: async (argv: YargsArgs) => buildHandler(argv.context.config),
+  handler: async (argv: YargsArgs) =>
+    buildHandler(argv.context.config, argv.analyze),
 };
 
 export * from './implementation';

packages/snaps-cli/src/commands/build/utils.test.ts

@@ -0,0 +1,70 @@
+import type { Compiler } from 'webpack';
+import { BundleAnalyzerPlugin } from 'webpack-bundle-analyzer';
+
+import { getBundleAnalyzerPort } from './utils';
+
+jest.mock('webpack-bundle-analyzer', () => ({
+  BundleAnalyzerPlugin: jest.fn(),
+}));
+
+describe('getBundleAnalyzerPort', () => {
+  it('returns the port of the bundle analyzer server', async () => {
+    const compiler: Compiler = {
+      // @ts-expect-error: Mock `Compiler` object.
+      options: {
+        plugins: [new BundleAnalyzerPlugin()],
+      },
+    };
+
+    const plugin = jest.mocked(BundleAnalyzerPlugin);
+    const instance = plugin.mock.instances[0];
+
+    // @ts-expect-error: Partial `server` mock.
+    instance.server = Promise.resolve({
+      http: {
+        address: () => 'http://localhost:8888',
+      },
+    });
+
+    const port = await getBundleAnalyzerPort(compiler);
+    expect(port).toBe(8888);
+  });
+
+  it('returns the port of the bundle analyzer server that returns an object', async () => {
+    const compiler: Compiler = {
+      // @ts-expect-error: Mock `Compiler` object.
+      options: {
+        plugins: [new BundleAnalyzerPlugin()],
+      },
+    };
+
+    const plugin = jest.mocked(BundleAnalyzerPlugin);
+    const instance = plugin.mock.instances[0];
+
+    // @ts-expect-error: Partial `server` mock.
+    instance.server = Promise.resolve({
+      http: {
+        address: () => {
+          return {
+            port: 8888,
+          };
+        },
+      },
+    });
+
+    const port = await getBundleAnalyzerPort(compiler);
+    expect(port).toBe(8888);
+  });
+
+  it('returns undefined if the bundle analyzer server is not available', async () => {
+    const compiler: Compiler = {
+      // @ts-expect-error: Mock `Compiler` object.
+      options: {
+        plugins: [new BundleAnalyzerPlugin()],
+      },
+    };
+
+    const port = await getBundleAnalyzerPort(compiler);
+    expect(port).toBeUndefined();
+  });
+});

packages/snaps-cli/src/commands/build/utils.ts

@@ -0,0 +1,29 @@
+import type { Compiler } from 'webpack';
+import { BundleAnalyzerPlugin } from 'webpack-bundle-analyzer';
+
+/**
+ * Get the port of the bundle analyzer server.
+ *
+ * @param compiler - The Webpack compiler.
+ * @returns The port of the bundle analyzer server.
+ */
+export async function getBundleAnalyzerPort(compiler: Compiler) {
+  const analyzerPlugin = compiler.options.plugins.find(
+    (plugin): plugin is BundleAnalyzerPlugin =>
+      plugin instanceof BundleAnalyzerPlugin,
+  );
+
+  if (analyzerPlugin?.server) {
+    const { http } = await analyzerPlugin.server;
+
+    const address = http.address();
+    if (typeof address === 'string') {
+      const { port } = new URL(address);
+      return parseInt(port, 10);
+    }
+
+    return address?.port;
+  }
+
+  return undefined;
+}

packages/snaps-cli/src/types/webpack-bundle-analyzer.d.ts

@@ -0,0 +1,22 @@
+declare module 'webpack-bundle-analyzer' {
+  import type { Server } from 'http';
+  import type { Compiler, WebpackPluginInstance } from 'webpack';
+
+  export type BundleAnalyzerPluginOptions = {
+    analyzerPort?: number | undefined;
+    logLevel?: 'info' | 'warn' | 'error' | 'silent' | undefined;
+    openAnalyzer?: boolean | undefined;
+  };
+
+  export class BundleAnalyzerPlugin implements WebpackPluginInstance {
+    readonly opts: BundleAnalyzerPluginOptions;
+
+    server?: Promise<{
+      http: Server;
+    }>;
+
+    constructor(options?: BundleAnalyzerPluginOptions);
+
+    apply(compiler: Compiler): void;
+  }
+}

packages/snaps-cli/src/types/yargs.d.ts

@@ -20,6 +20,7 @@ type YargsArgs = {
     config: ProcessedConfig;
   };
 
+  analyze?: boolean;
   fix?: boolean;
   input?: string;