fix(assets): Propagate sizes attribute on all sources

.changeset/tasty-oranges-bathe.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fix `sizes` attribute not being present on `source` elements when using it on the Picture component

packages/astro/components/Image.astro

@@ -1,6 +1,7 @@
 ---
 import { getImage, type LocalImageProps, type RemoteImageProps } from 'astro:assets';
 import { AstroError, AstroErrorData } from '../dist/core/errors/index.js';
+import type { HTMLAttributes } from '../types';
 
 // The TypeScript diagnostic for JSX props uses the last member of the union to suggest props, so it would be better for
 // LocalImageProps to be last. Unfortunately, when we do this the error messages that remote images get are complete nonsense
@@ -24,8 +25,7 @@ if (typeof props.height === 'string') {
 
 const image = await getImage(props);
 
-const additionalAttributes: Record<string, any> = {};
-
+const additionalAttributes: HTMLAttributes<'img'> = {};
 if (image.srcSet.values.length > 0) {
 	additionalAttributes.srcset = image.srcSet.attribute;
 }

packages/astro/components/Picture.astro

@@ -49,9 +49,16 @@ const fallbackImage = await getImage({
 	densities: props.densities,
 });
 
-const additionalAttributes: Record<string, any> = {};
+const imgAdditionalAttributes: HTMLAttributes<'img'> = {};
+const sourceAdditionaAttributes: HTMLAttributes<'source'> = {};
+
+// Propagate the `sizes` attribute to the `source` elements
+if (props.sizes) {
+	sourceAdditionaAttributes.sizes = props.sizes;
+}
+
 if (fallbackImage.srcSet.values.length > 0) {
-	additionalAttributes.srcset = fallbackImage.srcSet.attribute;
+	imgAdditionalAttributes.srcset = fallbackImage.srcSet.attribute;
 }
 ---
 
@@ -62,8 +69,14 @@ if (fallbackImage.srcSet.values.length > 0) {
 				props.densities || (!props.densities && !props.widths)
 					? `${image.src}${image.srcSet.values.length > 0 ? ', ' + image.srcSet.attribute : ''}`
 					: image.srcSet.attribute;
-			return <source srcset={srcsetAttribute} type={'image/' + image.options.format} />;
+			return (
+				<source
+					srcset={srcsetAttribute}
+					type={'image/' + image.options.format}
+					{...sourceAdditionaAttributes}
+				/>
+			);
 		})
 	}
-	<img src={fallbackImage.src} {...additionalAttributes} {...fallbackImage.attributes} />
+	<img src={fallbackImage.src} {...imgAdditionalAttributes} {...fallbackImage.attributes} />
 </picture>

packages/astro/src/assets/internal.ts

@@ -102,6 +102,7 @@ export async function getImage(
 	let imageURL = await service.getURL(validatedOptions, imageConfig);
 	let srcSets: SrcSetValue[] = await Promise.all(
 		srcSetTransforms.map(async (srcSet) => ({
+			transform: srcSet.transform,
 			url: await service.getURL(srcSet.transform, imageConfig),
 			descriptor: srcSet.descriptor,
 			attributes: srcSet.attributes,
@@ -115,6 +116,7 @@ export async function getImage(
 	) {
 		imageURL = globalThis.astroAsset.addStaticImage(validatedOptions);
 		srcSets = srcSetTransforms.map((srcSet) => ({
+			transform: srcSet.transform,
 			url: globalThis.astroAsset.addStaticImage!(srcSet.transform),
 			descriptor: srcSet.descriptor,
 			attributes: srcSet.attributes,

packages/astro/src/assets/services/service.ts

@@ -3,7 +3,7 @@ import { AstroError, AstroErrorData } from '../../core/errors/index.js';
 import { isRemotePath, joinPaths } from '../../core/path.js';
 import { DEFAULT_OUTPUT_FORMAT, VALID_SUPPORTED_FORMATS } from '../consts.js';
 import { isESMImportedImage, isRemoteAllowed } from '../internal.js';
-import type { ImageOutputFormat, ImageTransform } from '../types.js';
+import type { ImageOutputFormat, ImageTransform, UnresolvedSrcSetValue } from '../types.js';
 
 export type ImageService = LocalImageService | ExternalImageService;
 
@@ -28,12 +28,6 @@ type ImageConfig<T> = Omit<AstroConfig['image'], 'service'> & {
 	service: { entrypoint: string; config: T };
 };
 
-type SrcSetValue = {
-	transform: ImageTransform;
-	descriptor?: string;
-	attributes?: Record<string, any>;
-};
-
 interface SharedServiceProps<T extends Record<string, any> = Record<string, any>> {
 	/**
 	 * Return the URL to the endpoint or URL your images are generated from.
@@ -53,7 +47,7 @@ interface SharedServiceProps<T extends Record<string, any> = Record<string, any>
 	getSrcSet?: (
 		options: ImageTransform,
 		imageConfig: ImageConfig<T>
-	) => SrcSetValue[] | Promise<SrcSetValue[]>;
+	) => UnresolvedSrcSetValue[] | Promise<UnresolvedSrcSetValue[]>;
 	/**
 	 * Return any additional HTML attributes separate from `src` that your service requires to show the image properly.
 	 *
@@ -233,7 +227,7 @@ export const baseService: Omit<LocalImageService, 'transform'> = {
 		};
 	},
 	getSrcSet(options) {
-		const srcSet: SrcSetValue[] = [];
+		const srcSet: UnresolvedSrcSetValue[] = [];
 		const { targetWidth } = getTargetDimensions(options);
 		const { widths, densities } = options;
 		const targetFormat = options.format ?? DEFAULT_OUTPUT_FORMAT;

packages/astro/src/assets/types.ts

@@ -33,11 +33,18 @@ export interface ImageMetadata {
 	orientation?: number;
 }
 
-export interface SrcSetValue {
-	url: string;
+/**
+ * A yet to be completed with an url `SrcSetValue`. Other hooks will only see a resolved value, where the URL of the image has been added.
+ */
+export type UnresolvedSrcSetValue = {
+	transform: ImageTransform;
 	descriptor?: string;
-	attributes?: Record<string, string>;
-}
+	attributes?: Record<string, any>;
+};
+
+export type SrcSetValue = UnresolvedSrcSetValue & {
+	url: string;
+};
 
 /**
  * A yet to be resolved image transform. Used by `getImage`

packages/astro/test/core-image.test.js

@@ -222,6 +222,9 @@ describe('astro:image', () => {
 				expect($img).to.have.a.lengthOf(1);
 				expect($picture).to.have.a.lengthOf(1);
 				expect($source).to.have.a.lengthOf(1);
+				expect($source.attr('sizes')).to.equal(
+					'(max-width: 448px) 400px, (max-width: 810px) 750px, 1050px'
+				);
 
 				const srcset2 = parseSrcset($source.attr('srcset'));
 				expect(srcset2.every((src) => src.url.startsWith('/_image'))).to.equal(true);

packages/astro/test/fixtures/core-image/src/pages/picturecomponent.astro

@@ -8,7 +8,7 @@ import myImage from "../assets/penguin1.jpg";
 </div>
 
 <div id="picture-widths">
-<Picture src={myImage} width={Math.round(myImage.width / 2)} alt="A penguin" widths={[myImage.width]} />
+<Picture src={myImage} width={Math.round(myImage.width / 2)} alt="A penguin" widths={[myImage.width]} sizes="(max-width: 448px) 400px, (max-width: 810px) 750px, 1050px" />
 </div>
 
 <div id="picture-fallback">