feat(astro): Exposes extra APIs for script and testing (#12052)

Co-authored-by: Matt Kane <[email protected]> Co-authored-by: Sarah Rainsberger <[email protected]> Co-authored-by: Emanuele Stoppa <[email protected]> Co-authored-by: matthewp <[email protected]> Co-authored-by: sarah11918 <[email protected]> Co-authored-by: ematipico <[email protected]> Co-authored-by: bluwy <[email protected]> Co-authored-by: ascorbic <[email protected]> Co-authored-by: florian-lefebvre <[email protected]>
withastro · Feb 26, 2025 · 5be12b2 · 5be12b2
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diff --git a/.changeset/bright-eels-cross.md b/.changeset/bright-eels-cross.md
@@ -0,0 +1,23 @@
+---
+'astro': minor
+---
+
+Exposes extra APIs for scripting and testing.
+
+### Config helpers
+
+Two new helper functions exported from `astro/config`:
+
+- `mergeConfig()` allows users to merge partially defined Astro configurations on top of a base config while following the merge rules of `updateConfig()` available for integrations.
+- `validateConfig()` allows users to validate that a given value is a valid Astro configuration and fills in default values as necessary.
+
+These helpers are particularly useful for integration authors and for developers writing scripts that need to manipulate Astro configurations programmatically.
+
+### Programmatic build
+
+The `build` API now receives a second optional `BuildOptions` argument where users can specify:
+
+- `devOutput` (default `false`): output a development-based build similar to code transformed in `astro dev`.
+- `teardownCompiler` (default `true`): teardown the compiler WASM instance after build.
+
+These options provide more control when running Astro builds programmatically, especially for testing scenarios or custom build pipelines.
diff --git a/.changeset/slimy-cougars-worry.md b/.changeset/slimy-cougars-worry.md
@@ -0,0 +1,7 @@
+---
+'astro': patch
+---
+
+Fixes incorrect config update when calling `updateConfig` from `astro:build:setup` hook.
+
+The function previously called a custom update config function made for merging an Astro config. Now it calls the appropriate `mergeConfig()` utility exported by Vite that updates functional options correctly.
diff --git a/packages/astro/src/config/entrypoint.ts b/packages/astro/src/config/entrypoint.ts
@@ -5,6 +5,8 @@ import type { ImageServiceConfig } from '../types/public/index.js';
 
 export { defineConfig, getViteConfig } from './index.js';
 export { envField } from '../env/config.js';
+export { mergeConfig } from '../core/config/merge.js';
+export { validateConfig } from '../core/config/validate.js';
 
 /**
  * Return the configuration needed to use the Sharp-based image service

diff --git a/packages/astro/src/core/build/index.ts b/packages/astro/src/core/build/index.ts
@@ -45,7 +45,9 @@ export interface BuildOptions {
 	 * Teardown the compiler WASM instance after build. This can improve performance when
 	 * building once, but may cause a performance hit if building multiple times in a row.
 	 *
-	 * @internal only used for testing
+	 * When building multiple projects in the same execution (e.g. during tests), disabling
+	 * this option can greatly improve performance at the cost of some extra memory usage.
+	 *
 	 * @default true
 	 */
 	teardownCompiler?: boolean;

diff --git a/packages/astro/src/core/config/merge.ts b/packages/astro/src/core/config/merge.ts
@@ -1,5 +1,7 @@
 import { mergeConfig as mergeViteConfig } from 'vite';
 import { arraify, isObject, isURL } from '../util.js';
+import type { DeepPartial } from '../../type-utils.js';
+import type { AstroConfig, AstroInlineConfig } from '../../types/public/index.js';
 
 function mergeConfigRecursively(
 	defaults: Record<string, any>,
@@ -64,10 +66,9 @@ function mergeConfigRecursively(
 	return merged;
 }
 
-export function mergeConfig(
-	defaults: Record<string, any>,
-	overrides: Record<string, any>,
-	isRoot = true,
-): Record<string, any> {
-	return mergeConfigRecursively(defaults, overrides, isRoot ? '' : '.');
+export function mergeConfig<C extends AstroConfig | AstroInlineConfig>(
+	defaults: C,
+	overrides: DeepPartial<C>,
+): C {
+	return mergeConfigRecursively(defaults, overrides, '') as C;
 }
diff --git a/packages/astro/src/core/index.ts b/packages/astro/src/core/index.ts
@@ -4,18 +4,10 @@ import type { AstroInlineConfig } from '../types/public/config.js';
 import { default as _build } from './build/index.js';
 import { default as _sync } from './sync/index.js';
 
+export { default as build } from './build/index.js';
 export { default as dev } from './dev/index.js';
 export { default as preview } from './preview/index.js';
 
-/**
- * Builds your site for deployment. By default, this will generate static files and place them in a dist/ directory.
- * If SSR is enabled, this will generate the necessary server files to serve your site.
- *
- * @experimental The JavaScript API is experimental
- */
-// Wrap `_build` to prevent exposing the second internal options parameter
-export const build = (inlineConfig: AstroInlineConfig) => _build(inlineConfig);
-
 /**
  * Generates TypeScript types for all Astro modules. This sets up a `src/env.d.ts` file for type inferencing,
  * and defines the `astro:content` module for the Content Collections API.

diff --git a/packages/astro/src/integrations/hooks.ts b/packages/astro/src/integrations/hooks.ts
@@ -3,6 +3,7 @@ import type { AddressInfo } from 'node:net';
 import { fileURLToPath } from 'node:url';
 import { bold } from 'kleur/colors';
 import type { InlineConfig, ViteDevServer } from 'vite';
+import { mergeConfig as mergeViteConfig } from 'vite';
 import astroIntegrationActionsRouteHandler from '../actions/integration.js';
 import { isActionsFilePresent } from '../actions/utils.js';
 import { CONTENT_LAYER_TYPE } from '../content/consts.js';
@@ -196,7 +197,7 @@ export async function runHookConfigSetup({
 					updatedSettings.scripts.push({ stage, content });
 				},
 				updateConfig: (newConfig) => {
-					updatedConfig = mergeConfig(updatedConfig, newConfig) as AstroConfig;
+					updatedConfig = mergeConfig(updatedConfig, newConfig);
 					return { ...updatedConfig };
 				},
 				injectRoute: (injectRoute) => {
@@ -235,8 +236,7 @@ export async function runHookConfigSetup({
 					}
 					logger.debug(
 						'middleware',
-						`The integration ${integration.name} has added middleware that runs ${
-							order === 'pre' ? 'before' : 'after'
+						`The integration ${integration.name} has added middleware that runs ${order === 'pre' ? 'before' : 'after'
 						} any application middleware you define.`,
 					);
 					updatedSettings.middlewares[order].push(
@@ -510,7 +510,7 @@ export async function runHookBuildSetup({
 					pages,
 					target,
 					updateConfig: (newConfig) => {
-						updatedConfig = mergeConfig(updatedConfig, newConfig);
+						updatedConfig = mergeViteConfig(updatedConfig, newConfig);
 						return { ...updatedConfig };
 					},
 					logger: getLogger(integration, logger),
@@ -654,7 +654,7 @@ export async function runHookRouteSetup({
 		logger.debug(
 			'router',
 			`The ${route.component} route's prerender option has been changed multiple times by integrations:\n` +
-				prerenderChangeLogs.map((log) => `- ${log.integrationName}: ${log.value}`).join('\n'),
+			prerenderChangeLogs.map((log) => `- ${log.integrationName}: ${log.value}`).join('\n'),
 		);
 	}
 }