Move webpack cache to data root

webpack.config.js

@@ -1,35 +1,59 @@
 import process from 'node:process';
 import path from 'node:path';
+import os from 'node:os';
+import isDocker from 'is-docker';
 
-/** @type {import('webpack').Configuration} */
-export const publicLibConfig = {
-    mode: 'production',
-    entry: './public/lib.js',
-    cache: {
-        type: 'filesystem',
-        cacheDirectory: path.resolve(process.cwd(), 'dist/webpack'),
-        store: 'pack',
-        compression: 'gzip',
-    },
-    devtool: false,
-    watch: false,
-    module: {},
-    stats: {
-        preset: 'minimal',
-        assets: false,
-        modules: false,
-        colors: true,
-        timings: true,
-    },
-    experiments: {
-        outputModule: true,
-    },
-    performance: {
-        hints: false,
-    },
-    output: {
-        path: path.resolve(process.cwd(), 'dist'),
-        filename: 'lib.js',
-        libraryTarget: 'module',
-    },
-};
+/**
+ * Get the Webpack configuration for the public/lib.js file.
+ * @param {boolean} forceDist Whether to force the use the /dist folder.
+ * @returns {import('webpack').Configuration}
+ * */
+export default function getPublicLibConfig(forceDist = false) {
+    function getCacheDirectory() {
+        // Docker got cache pre-baked into the image.
+        if (forceDist || isDocker()) {
+            return path.resolve(process.cwd(), 'dist/webpack');
+        }
+
+        // Data root is set (should be the case 99.99% of the time).
+        if (typeof globalThis.DATA_ROOT === 'string') {
+            return path.resolve(globalThis.DATA_ROOT, '_cache', 'webpack');
+        }
+
+        // Fallback to the system temp directory.
+        return path.resolve(os.tmpdir(), 'webpack');
+    }
+
+    const cacheDirectory = getCacheDirectory();
+    return {
+        mode: 'production',
+        entry: './public/lib.js',
+        cache: {
+            type: 'filesystem',
+            cacheDirectory: cacheDirectory,
+            store: 'pack',
+            compression: 'gzip',
+        },
+        devtool: false,
+        watch: false,
+        module: {},
+        stats: {
+            preset: 'minimal',
+            assets: false,
+            modules: false,
+            colors: true,
+            timings: true,
+        },
+        experiments: {
+            outputModule: true,
+        },
+        performance: {
+            hints: false,
+        },
+        output: {
+            path: path.resolve(process.cwd(), 'dist'),
+            filename: 'lib.js',
+            libraryTarget: 'module',
+        },
+    };
+}