Use Node.js APIs for ext build script instead of shell commands

ext/build.js

@@ -1,65 +1,112 @@
 const fs = require("fs-extra");
 const path = require("path");
-const { spawn } = require("child_process");
 const minimist = require("minimist");
+const webpack = require("webpack");
+const webExt = require("web-ext").default;
+
+
+const DIST_PATH = path.join(__dirname, "../dist/ext");
+const UNPACKED_PATH = path.join(DIST_PATH, "unpacked");
 
 
 const argv = minimist(process.argv.slice(2), {
     boolean: [ "package", "watch" ]
   , string: [ "mirroringAppId", "mode" ]
   , default: {
-        package: false
-      , watch: false
-      , mirroringAppId: "19A6F4AE"
-      , mode: "development"
+        package: false             // Should package with web-ext
+      , watch: false               // Should run webpack in watch mode
+      , mirroringAppId: "19A6F4AE" // Chromecast mirroring receiver app ID
+      , mode: "development"        // webpack mode
     }
 });
 
+if (argv.package && argv.watch) {
+    console.error("Cannot package whilst watching files.");
+    process.exit(1);
+}
+
+// If packaging, use production mode
 if (argv.package) {
     argv.mode = "production";
-    argv.watch = false;
 }
 
 
-const extensionName = "fx_cast";
-const extensionId = "fx_cast@matt.tf";
-const extensionVersion = "0.0.1";
+// Import webpack config and specify env values
+const webpackConfig = require("./webpack.config.js")({
+    extensionName: "fx_cast"
+  , extensionId: "fx_cast@matt.tf"
+  , extensionVersion: "0.0.1"
+  , mirroringAppId: argv.mirroringAppId
+});
+
+// Add mode to config
+webpackConfig.mode = argv.mode;
+
+/**
+ * If watching files, output directly to dist. Unpacked
+ * directory is used as a staging area for web-ext builds.
+ */
+webpackConfig.output.path = argv.package
+    ? UNPACKED_PATH
+    : DIST_PATH;
 
-const DIST_PATH = path.join(__dirname, "../dist/ext");
-const UNPACKED_PATH = path.join(DIST_PATH, "unpacked");
 
 // Clean
 fs.removeSync(DIST_PATH);
 
-const buildCmd = `web-ext build --overwrite-dest `
-                             + `--source-dir ${UNPACKED_PATH} `
-                             + `--artifacts-dir ${DIST_PATH} `;
 
-const child = spawn(
-    `webpack --env.extensionName=${extensionName} `
-          + `--env.extensionId=${extensionId} `
-          + `--env.extensionVersion=${extensionVersion} `
-          + `--env.mirroringAppId=${argv.mirroringAppId} `
-          + `--mode=${argv.mode} `
-          + `${argv.watch ? "--watch" : ""} `
-    + `${argv.package ? "&&" + buildCmd : ""} `
-  , { shell: true }
-);
+// Create webpack compiler instance
+const compiler = webpack(webpackConfig);
 
-child.stdout.pipe(process.stdout);
-child.stderr.pipe(process.stderr);
+if (argv.watch) {
+    // Start webpack watch
+    compiler.watch({}, handleCompilerOutput);
+} else {
+    compiler.run((...args) => {
+        handleCompilerOutput(...args);
 
-child.on("exit", () => {
-    if (argv.package) {
-        fs.remove(UNPACKED_PATH);   
-    } else {
-        for (const file of fs.readdirSync(UNPACKED_PATH)) {
-            fs.moveSync(path.join(UNPACKED_PATH, file)
-                  , path.join(DIST_PATH, file)
-                  , { overwrite: true });
+        if (argv.package) {
+            webExt.cmd.build({
+                /**
+                 * Webpack output at sourceDir is built into an extension
+                 * archive at artifactsDir.
+                 */
+                sourceDir: UNPACKED_PATH
+              , artifactsDir: DIST_PATH
+              , overwriteDest: true
+            }, {
+                // Prevent auto-exit
+                shouldExitProgram: false
+
+            }).then(() => {
+                // Only need the built extension archive
+                fs.remove(UNPACKED_PATH);
+            })
+        }
+    });
+}
+
+/**
+ * Log errors and output formatted compilation info.
+ */
+function handleCompilerOutput (err, stats) {
+    // If there are fatal errors, log and exit
+    if (err) {
+        console.error(err.stack || err);
+        if (err.details) {
+            console.error(err.details);
         }
 
-        // Remove empty unpacked directory
-        fs.remove(UNPACKED_PATH);
+        return;
     }
-});
+
+    // Get compilation info
+    const info = stats.toJson();
+
+    // Log errors/warnings
+    if (stats.hasErrors()) console.error(info.errors);
+    if (stats.hasWarnings()) console.warn(info.warnings);
+
+    // Log formatted output
+    console.log(stats.toString());
+}