feat: allow users to store stats as json to a file

packages/webpack-cli/README.md

@@ -36,28 +36,28 @@ yarn add webpack-cli --dev
 ### webpack 4
 
 ```
-  --entry string[]         The entry point(s) of your application.
-  -c, --config string[]    Provide path to webpack configuration file(s)
-  --config-name string[]   Name of the configuration to use
-  -m, --merge              Merge several configurations using webpack-merge
-  --progress               Print compilation progress during build
-  --color                  Enables colors on console
-  --no-color               Disable colors on console
-  --env string             Environment passed to the configuration when it is a function
-  --name string            Name of the configuration. Used when loading multiple configurations
-  --help                   Outputs list of supported flags
-  -o, --output string      Output location of the file generated by webpack
-  -t, --target string      Sets the build target
-  -w, --watch              Watch for files changes
-  -h, --hot                Enables Hot Module Replacement
-  --no-hot                 Disables Hot Module Replacement
-  -d, --devtool string     Controls if and how source maps are generated.
-  --prefetch string        Prefetch this request
-  -j, --json               Prints result as JSON
-  --mode string            Defines the mode to pass to webpack
-  -v, --version            Get current version
-  --stats string           It instructs webpack on how to treat the stats
-  --no-stats               Disables stats output
+  --entry string[]              The entry point(s) of your application.
+  -c, --config string[]         Provide path to webpack configuration file(s)
+  --config-name string[]        Name of the configuration to use
+  -m, --merge                   Merge several configurations using webpack-merge
+  --progress                    Print compilation progress during build
+  --color                       Enables colors on console
+  --no-color                    Disable colors on console
+  --env string                  Environment passed to the configuration when it is a function
+  --name string                 Name of the configuration. Used when loading multiple configurations
+  --help                        Outputs list of supported flags
+  -o, --output string           Output location of the file generated by webpack
+  -t, --target string           Sets the build target
+  -w, --watch                   Watch for files changes
+  -h, --hot                     Enables Hot Module Replacement
+  --no-hot                      Disables Hot Module Replacement
+  -d, --devtool string          Controls if and how source maps are generated.
+  --prefetch string             Prefetch this request
+  -j, --json string, boolean    Prints result as JSON or store it in a file
+  --mode string                 Defines the mode to pass to webpack
+  -v, --version                 Get current version
+  --stats string, boolean       It instructs webpack on how to treat the stats
+  --no-stats                    Disables stats output
 ```
 
 ### webpack 5

packages/webpack-cli/lib/groups/resolveStats.js

@@ -14,7 +14,7 @@ const resolveStats = (args) => {
         finalOptions.options.stats = stats;
     }
     if (json) {
-        finalOptions.outputOptions.json = true;
+        finalOptions.outputOptions.json = json;
     }
     return finalOptions;
 };

packages/webpack-cli/lib/utils/Compiler.js

@@ -1,6 +1,7 @@
 const { packageExists } = require('@webpack-cli/package-utils');
 const webpack = packageExists('webpack') ? require('webpack') : undefined;
 const logger = require('./logger');
+const { writeFileSync } = require('fs');
 const bailAndWatchWarning = require('./warnings/bailAndWatchWarning');
 const { CompilerOutput } = require('./CompilerOutput');
 
@@ -58,7 +59,7 @@ class Compiler {
         if (!outputOptions.watch && (stats.hasErrors() || stats.hasWarnings())) {
             process.exitCode = 1;
         }
-        if (outputOptions.json) {
+        if (outputOptions.json === true) {
             process.stdout.write(JSON.stringify(stats.toJson(outputOptions), null, 2) + '\n');
         } else if (stats.hash !== lastHash) {
             lastHash = stats.hash;
@@ -69,6 +70,15 @@ class Compiler {
                     statsErrors.push({ name: statErr.message, loc: errLoc });
                 });
             }
+            const JSONStats = JSON.stringify(stats.toJson(outputOptions), null, 2);
+            if (typeof outputOptions.json === 'string') {
+                try {
+                    writeFileSync(outputOptions.json, JSONStats);
+                    logger.info(`stats are successfully stored as json to ${outputOptions.json}`);
+                } catch (err) {
+                    logger.error(err);
+                }
+            }
             return this.generateOutput(outputOptions, stats, statsErrors);
         }
     }

packages/webpack-cli/lib/utils/cli-flags.js

@@ -174,9 +174,9 @@ const core = [
     {
         name: 'json',
         usage: '--json',
-        type: Boolean,
+        type: [String, Boolean],
         alias: 'j',
-        description: 'Prints result as JSON',
+        description: 'Prints result as JSON or store it in a file',
     },
     {
         name: 'mode',

scripts/cleanupTest.js

@@ -3,7 +3,7 @@ const rimraf = require('rimraf');
 const { join } = require('path');
 const collectTestFolders = require('./utils');
 
-const outputDirectories = ['bin', 'binary', 'dist', 'test', 'test-assets', 'test-plugin', 'test-loader'];
+const outputDirectories = ['bin', 'binary', 'dist', 'test', 'test-assets', 'test-plugin', 'test-loader', 'stats.json'];
 
 function folderStrategy(stats, file) {
     return stats.isDirectory() && outputDirectories.includes(file);

test/json/json.test.js

@@ -1,5 +1,7 @@
 'use strict';
 const { run } = require('../utils/test-utils');
+const { stat, readFile } = require('fs');
+const { resolve } = require('path');
 
 describe('json flag', () => {
     it('should return valid json', () => {
@@ -10,9 +12,31 @@ describe('json flag', () => {
             return JSON.parse(stdout);
         };
         // check the JSON is valid.
+        expect(JSON.parse(stdout)['hash']).toBeTruthy();
+        expect(JSON.parse(stdout)['version']).toBeTruthy();
+        expect(JSON.parse(stdout)['time']).toBeTruthy();
         expect(parseJson).not.toThrow();
     });
 
+    it('should store json to a file', (done) => {
+        const { stdout } = run(__dirname, ['--json', 'stats.json']);
+
+        expect(stdout).toContain('stats are successfully stored as json to stats.json');
+        stat(resolve(__dirname, './stats.json'), (err, stats) => {
+            expect(err).toBe(null);
+            expect(stats.isFile()).toBe(true);
+            done();
+        });
+        readFile(resolve(__dirname, 'stats.json'), 'utf-8', (err, data) => {
+            expect(err).toBe(null);
+            expect(JSON.parse(data)['hash']).toBeTruthy();
+            expect(JSON.parse(data)['version']).toBeTruthy();
+            expect(JSON.parse(data)['time']).toBeTruthy();
+            expect(() => JSON.parse(data)).not.toThrow();
+            done();
+        });
+    });
+
     it('should return valid json with -j alias', () => {
         const { stdout } = run(__dirname, ['-j']);
 
@@ -21,6 +45,9 @@ describe('json flag', () => {
             return JSON.parse(stdout);
         };
         // check the JSON is valid.
+        expect(JSON.parse(stdout)['hash']).toBeTruthy();
+        expect(JSON.parse(stdout)['version']).toBeTruthy();
+        expect(JSON.parse(stdout)['time']).toBeTruthy();
         expect(parseJson).not.toThrow();
     });
 });