support og:image:alt from discovered images

Author: cscheid

src/project/types/website/listing/website-listing-feed.ts

@@ -163,7 +163,7 @@ export async function createFeed(
 
   // Add any image metadata
   const image = options.image || format.metadata[kImage] as string ||
-    websiteImage(project.config);
+    websiteImage(project.config)?.src;
   if (image) {
     feed.image = {
       title: feedTitle,

src/project/types/website/util/discover-meta.ts

@@ -41,12 +41,16 @@ export function findDescription(doc: Document): string | undefined {
 
 export function findPreviewImg(
   doc: Document,
-): string | undefined {
+): { src: string; alt?: string } | undefined {
   const imgEl = findPreviewImgEl(doc);
   if (imgEl) {
     const src = getDecodedAttribute(imgEl, "src");
+    const alt = getDecodedAttribute(imgEl, "alt");
     if (src !== null) {
-      return src;
+      return {
+        src,
+        alt: alt ?? undefined,
+      };
     } else {
       return undefined;
     }

src/project/types/website/website-config.ts

@@ -50,6 +50,7 @@ import { join } from "../../../deno_ral/path.ts";
 type WebsiteConfigKey =
   | "title"
   | "image"
+  | "image-alt"
   | "description"
   | "favicon"
   | "site-url"
@@ -173,8 +174,16 @@ export function websiteBaseurl(project?: ProjectConfig): string | undefined {
   return websiteConfigString(kSiteUrl, project);
 }
 
-export function websiteImage(project?: ProjectConfig): string | undefined {
-  return websiteConfigString(kImage, project);
+export function websiteImage(
+  project?: ProjectConfig,
+): { src: string; alt?: string } | undefined {
+  const src = websiteConfigString(kImage, project);
+  if (src) {
+    const alt = websiteConfigString("image-alt", project);
+    return { src, alt };
+  } else {
+    return undefined;
+  }
 }
 
 export function websiteDescription(

src/project/types/website/website-meta.ts

@@ -180,8 +180,9 @@ export function metadataHtmlPostProcessor(
 
       // find a preview image if one is not provided
       if (metadata[kImage] === undefined && format.metadata[kImage] !== false) {
-        metadata[kImage] = findPreviewImg(doc) ||
-          websiteImage(project.config);
+        const previewImg = findPreviewImg(doc) || websiteImage(project.config);
+        metadata[kImage] = previewImg ? previewImg.src : undefined;
+        metadata[kImageAlt] = previewImg ? previewImg.alt : undefined;
       }
 
       // cook up a description if one is not provided