fix: move webpack/rspack helper file out of outDir

.gitignore

@@ -15,3 +15,8 @@ yarn-error.log
 node_modules/
 dist/
 dist-basic/
+
+.vitrine/*
+!.vitrine/project.json
+!.vitrine/plans
+!.vitrine/assets

packages/plugins/injection/src/index.test.ts

@@ -2,24 +2,32 @@
 // This product includes software developed at Datadog (https://www.datadoghq.com/).
 // Copyright 2019-Present Datadog, Inc.
 
+import { datadogRspackPlugin } from '@datadog/rspack-plugin';
+import { datadogWebpackPlugin } from '@datadog/webpack-plugin';
 import { outputFileSync } from '@dd/core/helpers/fs';
+import { getUniqueId } from '@dd/core/helpers/strings';
 import type { Assign, BundlerName, Options, ToInjectItem } from '@dd/core/types';
 import { InjectPosition } from '@dd/core/types';
 import { AFTER_INJECTION, BEFORE_INJECTION } from '@dd/internal-injection-plugin/constants';
 import { addInjections, isFileSupported } from '@dd/internal-injection-plugin/helpers';
+import { getOutDir, prepareWorkingDir } from '@dd/tests/_jest/helpers/env';
 import {
     hardProjectEntries,
     defaultPluginOptions,
     easyProjectWithCSSEntry,
 } from '@dd/tests/_jest/helpers/mocks';
 import { BUNDLERS, runBundlers } from '@dd/tests/_jest/helpers/runBundlers';
+import type { BundlerConfigFunction } from '@dd/tools/bundlers';
+import { configRspack, configWebpack } from '@dd/tools/bundlers';
 import { header, licenses } from '@dd/tools/commands/oss/templates';
 import { escapeStringForRegExp, execute, red } from '@dd/tools/helpers';
+import { rspack } from '@rspack/core';
 import chalk from 'chalk';
 import { readFileSync } from 'fs';
 import { glob } from 'glob';
 import nock from 'nock';
 import path from 'path';
+import webpack from 'webpack';
 
 const FAKE_FILE_PREFIX = 'fake-file-to-inject-';
 // Files that we will execute part of the test.
@@ -578,4 +586,71 @@ describe('Injection Plugin', () => {
             });
         });
     });
+
+    // Regression test for https://github.com/DataDog/build-plugins/issues/304
+    // When output.clean is enabled, webpack/rspack deletes the helper file from outDir
+    // during emit. On subsequent rebuilds (watch/dev mode), the file is gone and
+    // module resolution fails.
+    // We reproduce this by creating a compiler once and running it twice (no close()
+    // in between), simulating what happens in dev server / watch mode.
+    describe('output.clean compatibility', () => {
+        const xpackCases: {
+            name: string;
+            bundle: any;
+            config: BundlerConfigFunction;
+            plugin: any;
+        }[] = [
+            {
+                name: 'webpack',
+                bundle: webpack,
+                config: configWebpack,
+                plugin: datadogWebpackPlugin,
+            },
+            { name: 'rspack', bundle: rspack, config: configRspack, plugin: datadogRspackPlugin },
+        ];
+
+        test.each(xpackCases)(
+            '$name | Should survive rebuilds with output.clean: true',
+            async ({ bundle, config, plugin }) => {
+                const seed = `clean-test.${getUniqueId()}`;
+                const workingDir = await prepareWorkingDir(seed);
+                const outDir = getOutDir(workingDir, 'clean');
+
+                // Create one compiler and run it twice to simulate watch/dev-mode rebuilds.
+                // With the bug, output.clean deletes the helper file from outDir
+                // during the first build's emit, so the second build's resolution fails.
+                const compiler: any = bundle(
+                    config({
+                        workingDir,
+                        outDir,
+                        entry: { main: easyProjectWithCSSEntry },
+                        node: true,
+                        clean: true,
+                        plugins: [plugin(defaultPluginOptions)],
+                    }),
+                );
+
+                const run = () =>
+                    new Promise<void>((resolve, reject) => {
+                        compiler.run((err: any, stats: any) => {
+                            if (err) {
+                                return reject(err);
+                            }
+                            const { errors } = stats!.compilation;
+                            if (errors?.length) {
+                                return reject(errors[0]);
+                            }
+                            resolve();
+                        });
+                    });
+
+                try {
+                    await expect(run()).resolves.toBeUndefined();
+                    await expect(run()).resolves.toBeUndefined();
+                } finally {
+                    await new Promise<void>((resolve) => compiler.close(() => resolve()));
+                }
+            },
+        );
+    });
 });

packages/plugins/injection/src/xpack.ts

@@ -25,8 +25,15 @@ export const getXpackPlugin =
         // Use a narrower identifier to avoid cross build collisions.
         const ConcatSource = bundler.sources.ConcatSource;
         const id = context.bundler.name;
+        // Use a cache directory within the project root instead of outDir,
+        // so that webpack's output.clean option doesn't delete the file
+        // before it can be resolved as an entry point.
+        // https://github.com/DataDog/build-plugins/issues/304
         const filePath = path.resolve(
-            context.bundler.outDir,
+            context.buildRoot,
+            'node_modules',
+            '.cache',
+            'datadog-build-plugins',
             `${id}.${InjectPosition.MIDDLE}.${INJECTED_FILE}.js`,
         );
 

packages/tools/src/bundlers.ts

@@ -31,6 +31,7 @@ export type BundlerConfig = {
     node?: boolean;
     plugins?: any[];
     splitting?: boolean; // Enable code splitting for dynamic imports
+    clean?: boolean; // Enable output.clean for webpack/rspack
 };
 export type BundlerConfigFunction = (config: BundlerConfig) => BundlerOptions;
 export type BundlerRunFn = (bundlerConfig: any) => Promise<{ errors: string[]; result?: any }>;
@@ -201,6 +202,7 @@ export const configXpack = (config: BundlerConfig): Configuration & RspackOption
             path: config.outDir,
             filename: `[name].js`,
             chunkFilename: 'chunk.[contenthash].js',
+            clean: config.clean,
         },
         devtool: 'source-map',
         optimization: {
@@ -319,7 +321,7 @@ export const configVite = (config: BundlerConfig): UserConfig => {
     return {
         root: config.workingDir,
         build: {
-            emptyOutDir: false,
+            emptyOutDir: config.clean ?? false,
             assetsDir: '', // Disable assets dir to simplify the test.
             minify: false,
             rollupOptions: baseConfig,