feat: built in env files support

packages/dotenv-webpack-plugin/package.json

@@ -0,0 +1,17 @@
+{
+  "name": "dotenv-webpack-plugin",
+  "version": "1.0.0",
+  "description": "A webpack plugin to support env files",
+  "main": "index.js",
+  "repository": "https://github.com/webpack/webpack-cli",
+  "author": "Burhanuddin Udaipurwala (burhanuday)",
+  "license": "MIT",
+  "private": true,
+  "dependencies": {
+    "dotenv": "^16.0.3",
+    "dotenv-expand": "^10.0.0"
+  },
+  "peerDependencies": {
+    "webpack": "5.x.x"
+  }
+}

packages/dotenv-webpack-plugin/src/index.js

@@ -0,0 +1,68 @@
+const fs = require("fs");
+const path = require("path");
+const dotenv = require("dotenv");
+const dotenvExpand = require("dotenv-expand");
+const { DefinePlugin } = require("webpack");
+
+class DotenvWebpackPlugin {
+  constructor(config = {}) {
+    this.config = Object.assign(
+      {},
+      {
+        envFiles: [],
+        prefixes: ["process.env.", "import.meta.env."],
+      },
+      config,
+    );
+    this.cache = new Map();
+  }
+
+  apply(compiler) {
+    const currentDirectory = path.resolve(process.cwd(), "environment");
+
+    const mode = compiler.options.mode || "development";
+    // .local file variables will get precedence
+    const environmentFiles =
+      this.config.envFiles.length > 0
+        ? this.config.envFiles
+        : [
+            `${currentDirectory}/.env`, // loaded in all cases
+            `${currentDirectory}/.env.local`, // loaded in all cases, ignored by git
+            `${currentDirectory}/.env.${mode}`, // only loaded in specified mode
+            `${currentDirectory}/.env.${mode}.local`, // only loaded in specified mode, ignored by git
+          ];
+
+    let envVariables = {};
+    // parse environment vars from .env files
+    environmentFiles.forEach((environmentFile) => {
+      if (fs.existsSync(environmentFile)) {
+        try {
+          const environmentFileContents = fs.readFileSync(environmentFile);
+          const parsedEnvVariables = dotenv.parse(environmentFileContents);
+          for (const [key, value] of Object.entries(parsedEnvVariables)) {
+            // only add variables starting with WEBPACK_
+            if (key.startsWith("WEBPACK_")) {
+              for (let index = 0; index < this.config.prefixes.length; index++) {
+                const prefix = this.config.prefixes[index];
+                envVariables[`${prefix}${key}`] = value;
+              }
+            }
+          }
+        } catch (err) {
+          this.logger.error(`Could not read ${environmentFile}`);
+        }
+      }
+    });
+
+    // expand environment vars
+    envVariables = dotenvExpand({
+      parsed: envVariables,
+      // don't write to process.env
+      ignoreProcessEnv: true,
+    }).parsed;
+
+    new DefinePlugin(envVariables).apply(compiler);
+  }
+}
+
+module.exports = DotenvWebpackPlugin;

packages/webpack-cli/src/webpack-cli.ts

@@ -45,7 +45,7 @@ import {
 
 import webpackMerge from "webpack-merge";
 import webpack from "webpack";
-import { Compiler, MultiCompiler, WebpackError, StatsOptions } from "webpack";
+import { Compiler, MultiCompiler, WebpackError, StatsOptions, Configuration } from "webpack";
 import { stringifyStream } from "@discoveryjs/json-ext";
 import { Help, ParseOptions } from "commander";
 
@@ -1952,7 +1952,6 @@ class WebpackCLI implements IWebpackCLI {
       }, {});
       config.path.set(config.options, mergedConfigPaths as unknown as string);
     }
-
     return config;
   }