Extract shared vite.build config for production and dev backend builds

sdkennedy2 · claude · sdkennedy2 · commit 0de87246e52c · 2026-03-30T14:52:56.000-04:00
Move common build options (configFile, logLevel, minify, target,
treeshake, preserveEntrySignatures, onwarn, resolve, output format,
and virtual module plugin) into a shared getBaseBackendBuildConfig()
helper. Each caller now only specifies what differs: production writes
multi-entry output to disk, dev builds a single function in-memory.

Co-Authored-By: Claude Opus 4.6 (1M context) &lt;noreply@anthropic.com&gt;
diff --git a/packages/plugins/apps/src/backend/vite/build-config.ts b/packages/plugins/apps/src/backend/vite/build-config.ts
@@ -0,0 +1,65 @@
+// Unless explicitly stated otherwise all files in this repository are licensed under the MIT License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2019-Present Datadog, Inc.
+
+import type { BuildOptions, InlineConfig, Plugin } from 'vite';
+
+/**
+ * Create the virtual module resolver plugin used by both production and dev builds.
+ * Maps virtual IDs to their generated source content.
+ */
+export function createVirtualPlugin(name: string, virtualEntries: Record<string, string>): Plugin {
+    return {
+        name,
+        enforce: 'pre',
+        resolveId(id: string) {
+            if (virtualEntries[id]) {
+                return { id, moduleSideEffects: true };
+            }
+            return null;
+        },
+        load(id: string) {
+            if (virtualEntries[id]) {
+                return virtualEntries[id];
+            }
+            return null;
+        },
+    };
+}
+
+/**
+ * Shared Vite/Rollup config for building backend functions.
+ * Both the production build (write to disk) and dev build (in-memory)
+ * use this as a base, overriding only what differs.
+ */
+export function getBaseBackendBuildConfig(
+    root: string,
+    virtualEntries: Record<string, string>,
+): InlineConfig & {
+    build: BuildOptions & { rollupOptions: NonNullable<BuildOptions['rollupOptions']> };
+} {
+    return {
+        configFile: false,
+        root,
+        logLevel: 'silent',
+        build: {
+            minify: false,
+            target: 'esnext',
+            rollupOptions: {
+                output: { format: 'es', exports: 'named' },
+                preserveEntrySignatures: 'exports-only',
+                treeshake: false,
+                onwarn(warning, defaultHandler) {
+                    if (warning.code === 'MODULE_LEVEL_DIRECTIVE') {
+                        return;
+                    }
+                    defaultHandler(warning);
+                },
+            },
+        },
+        resolve: {
+            extensions: ['.ts', '.tsx', '.js', '.jsx', '.mjs', '.cjs', '.json'],
+        },
+        plugins: [createVirtualPlugin('dd-backend-resolve', virtualEntries)],
+    };
+}
diff --git a/packages/plugins/apps/src/backend/vite/dev-server.ts b/packages/plugins/apps/src/backend/vite/dev-server.ts
@@ -13,6 +13,8 @@ import type { build } from 'vite';
 import type { BackendFunction } from '../discovery';
 import { generateDevVirtualEntryContent } from '../virtual-entry';
 
+import { getBaseBackendBuildConfig } from './build-config';
+
 type BundleFn = (func: BackendFunction, args: unknown[]) => Promise<string>;
 
 const DEV_VIRTUAL_PREFIX = 'virtual:dd-backend-dev:';
@@ -71,56 +73,25 @@ async function bundleBackendFunction(
 
     log.debug(`Bundling backend function "${func.name}" from ${func.entryPath}`);
 
+    const baseConfig = getBaseBackendBuildConfig(projectRoot, { [virtualId]: virtualContent });
+
+    // Dev: build a single function in-memory per request so we can send the
+    // bundled script to the Datadog API without writing temp files.
+    // Uses a plain "virtual:" prefix instead of \0 because Rollup generates
+    // empty chunks when \0-prefixed IDs are used as input entries.
+    // inlineDynamicImports collapses everything into one chunk since we only
+    // have a single entry (incompatible with multi-entry builds).
     const result = await viteBuild({
-        configFile: false,
-        root: projectRoot,
-        logLevel: 'silent',
+        ...baseConfig,
         build: {
+            ...baseConfig.build,
             write: false,
-            minify: false,
-            // Target esnext to avoid unnecessary transforms.
-            target: 'esnext',
             rollupOptions: {
+                ...baseConfig.build.rollupOptions,
                 input: virtualId,
-                output: { format: 'es', exports: 'named', inlineDynamicImports: true },
-                treeshake: false,
-                // Disable tree-shaking so action-catalog bridges and argument passing stay
-                // fully intact in the generated backend bundle.
-                // preserveEntrySignatures ensures the main() export isn't removed.
-                preserveEntrySignatures: 'exports-only',
-                // Silence "use client" directive warnings from third-party deps.
-                // eslint-disable-next-line @typescript-eslint/no-explicit-any
-                onwarn(warning: any, defaultHandler: any) {
-                    if (warning.code === 'MODULE_LEVEL_DIRECTIVE') {
-                        return;
-                    }
-                    defaultHandler(warning);
-                },
+                output: { ...baseConfig.build.rollupOptions.output, inlineDynamicImports: true },
             },
         },
-        // Re-enable Vite's built-in resolve and esbuild transform for TypeScript support.
-        // Without this, .ts imports from the virtual entry won't be processed.
-        resolve: {
-            extensions: ['.ts', '.tsx', '.js', '.jsx', '.mjs', '.cjs', '.json'],
-        },
-        plugins: [
-            {
-                name: 'dd-backend-dev-resolve',
-                enforce: 'pre',
-                resolveId(id: string) {
-                    if (id === virtualId) {
-                        return { id, moduleSideEffects: true };
-                    }
-                    return null;
-                },
-                load(id: string) {
-                    if (id === virtualId) {
-                        return virtualContent;
-                    }
-                    return null;
-                },
-            },
-        ],
     });
 
     const output = Array.isArray(result) ? result[0] : result;
diff --git a/packages/plugins/apps/src/backend/vite/index.ts b/packages/plugins/apps/src/backend/vite/index.ts
@@ -11,6 +11,7 @@ import type { build } from 'vite';
 import type { BackendFunction } from '../discovery';
 import { generateVirtualEntryContent } from '../virtual-entry';
 
+import { getBaseBackendBuildConfig } from './build-config';
 import { createDevServerMiddleware } from './dev-server';
 
 const VIRTUAL_PREFIX = '\0dd-backend:';
@@ -43,50 +44,25 @@ async function buildBackendFunctions(
 
     log.debug(`Building ${functions.length} backend function(s) via vite.build()`);
 
+    const baseConfig = getBaseBackendBuildConfig(buildRoot, virtualEntries);
+
+    // Production: build all functions in one vite.build() call, writing each to
+    // disk as a named file so the archive/upload step can collect them.
+    // Uses multi-entry input (one per function) with \0-prefixed virtual IDs —
+    // the \0 convention prevents other plugins from processing these IDs.
     const result = await viteBuild({
-        configFile: false,
-        root: buildRoot,
-        logLevel: 'silent',
+        ...baseConfig,
         build: {
+            ...baseConfig.build,
             write: true,
             outDir,
             emptyOutDir: false,
-            minify: false,
-            target: 'esnext',
             rollupOptions: {
+                ...baseConfig.build.rollupOptions,
                 input,
-                output: { format: 'es', exports: 'named', entryFileNames: '[name].js' },
-                preserveEntrySignatures: 'exports-only',
-                treeshake: false,
-                onwarn(warning, defaultHandler) {
-                    if (warning.code === 'MODULE_LEVEL_DIRECTIVE') {
-                        return;
-                    }
-                    defaultHandler(warning);
-                },
+                output: { ...baseConfig.build.rollupOptions.output, entryFileNames: '[name].js' },
             },
         },
-        resolve: {
-            extensions: ['.ts', '.tsx', '.js', '.jsx', '.mjs', '.cjs', '.json'],
-        },
-        plugins: [
-            {
-                name: 'dd-backend-resolve',
-                enforce: 'pre',
-                resolveId(id: string) {
-                    if (virtualEntries[id]) {
-                        return { id, moduleSideEffects: true };
-                    }
-                    return null;
-                },
-                load(id: string) {
-                    if (virtualEntries[id]) {
-                        return virtualEntries[id];
-                    }
-                    return null;
-                },
-            },
-        ],
     });
 
     const output = Array.isArray(result) ? result[0] : result;
