feat: Improve type inference for oEmbed type in TypeScript (#113)

Co-authored-by: jack <8209433+jacktuck@users.noreply.github.com>

Author: r4ai

README.md

@@ -58,21 +58,7 @@ type Metadata = {
   author?: string
   theme_color?: string
   canonical_url?: string
-  oEmbed?: {
-    type: 'photo' | 'video' | 'link' | 'rich'
-    version?: string
-    title?: string
-    author_name?: string
-    author_url?: string
-    provider_name?: string
-    provider_url?: string
-    cache_age?: number
-    thumbnails?: [{
-      url?: string
-      width?: number
-      height?: number
-    }]
-  }
+  oEmbed?: OEmbedPhoto | OEmbedVideo | OEmbedLink | OEmbedRich
   twitter_card: {
     card: string
     site?: string
@@ -147,6 +133,49 @@ type Metadata = {
     }
   }
 }
+
+type OEmbedBase = {
+  type: "photo" | "video" | "link" | "rich"
+  version: string
+  title?: string
+  author_name?: string
+  author_url?: string
+  provider_name?: string
+  provider_url?: string
+  cache_age?: number
+  thumbnails?: [
+    {
+      url?: string
+      width?: number
+      height?: number
+    }
+  ]
+}
+
+type OEmbedPhoto = OEmbedBase & {
+  type: "photo"
+  url: string
+  width: number
+  height: number
+}
+
+type OEmbedVideo = OEmbedBase & {
+  type: "video"
+  html: string
+  width: number
+  height: number
+}
+
+type OEmbedLink = OEmbedBase & {
+  type: "link"
+}
+
+type OEmbedRich = OEmbedBase & {
+  type: "rich"
+  html: string
+  width: number
+  height: number
+}
 ```
 
 ## The who 💖

src/types.ts

@@ -24,25 +24,7 @@ export type Metadata = {
   author?: string;
   theme_color?: string;
   canonical_url?: string;
-  oEmbed?: {
-    type: "photo" | "video" | "link" | "rich";
-    width?: number;
-    height?: number;
-    version?: string;
-    title?: string;
-    author_name?: string;
-    author_url?: string;
-    provider_name?: string;
-    provider_url?: string;
-    cache_age?: number;
-    thumbnails?: [
-      {
-        url?: string;
-        width?: number;
-        height?: number;
-      }
-    ];
-  };
+  oEmbed?: OEmbedPhoto | OEmbedVideo | OEmbedLink | OEmbedRich;
   twitter_card: {
     card: string;
     site?: string;
@@ -117,3 +99,46 @@ export type Metadata = {
     };
   };
 };
+
+type OEmbedBase = {
+  type: "photo" | "video" | "link" | "rich";
+  version: string;
+  title?: string;
+  author_name?: string;
+  author_url?: string;
+  provider_name?: string;
+  provider_url?: string;
+  cache_age?: number;
+  thumbnails?: [
+    {
+      url?: string;
+      width?: number;
+      height?: number;
+    }
+  ];
+};
+
+type OEmbedPhoto = OEmbedBase & {
+  type: "photo";
+  url: string;
+  width: number;
+  height: number;
+};
+
+type OEmbedVideo = OEmbedBase & {
+  type: "video";
+  html: string;
+  width: number;
+  height: number;
+};
+
+type OEmbedLink = OEmbedBase & {
+  type: "link";
+};
+
+type OEmbedRich = OEmbedBase & {
+  type: "rich";
+  html: string;
+  width: number;
+  height: number;
+};

test/oembed/test.ts

@@ -32,11 +32,15 @@ test("width/height should be numbers", async () => {
 
   const result = await unfurl("http://localhost/html/oembed");
 
-  expect(result.oEmbed.width).toEqual(640);
-  expect(result.oEmbed.height).toEqual(640);
+  expect(result.oEmbed?.type).toEqual("video");
+  const oEmbed =
+    result.oEmbed?.type === "video" ? result.oEmbed : (result.oEmbed as never);
 
-  expect(result.oEmbed.thumbnails[0].width).toEqual(200);
-  expect(result.oEmbed.thumbnails[0].height).toEqual(200);
+  expect(oEmbed.width).toEqual(640);
+  expect(oEmbed.height).toEqual(640);
+
+  expect(oEmbed.thumbnails?.[0].width).toEqual(200);
+  expect(oEmbed.thumbnails?.[0].height).toEqual(200);
 });
 
 test("should decode entities in OEmbed URL", async () => {
@@ -54,11 +58,15 @@ test("should decode entities in OEmbed URL", async () => {
 
   const result = await unfurl("http://localhost/html/oembed");
 
-  expect(result.oEmbed.width).toEqual(640);
-  expect(result.oEmbed.height).toEqual(640);
+  expect(result.oEmbed?.type).toEqual("video");
+  const oEmbed =
+    result.oEmbed?.type === "video" ? result.oEmbed : (result.oEmbed as never);
+
+  expect(oEmbed.width).toEqual(640);
+  expect(oEmbed.height).toEqual(640);
 
-  expect(result.oEmbed.thumbnails[0].width).toEqual(200);
-  expect(result.oEmbed.thumbnails[0].height).toEqual(200);
+  expect(oEmbed.thumbnails?.[0].width).toEqual(200);
+  expect(oEmbed.thumbnails?.[0].height).toEqual(200);
 });
 
 test("should prefer fetching JSON oEmbed", async () => {
@@ -118,7 +126,7 @@ test("should upgrade to HTTPS if needed", async () => {
 
   const result = await unfurl("http://localhost/html/oembed-http");
 
-  expect(result.oEmbed.version).toEqual("1.0");
+  expect(result.oEmbed?.version).toEqual("1.0");
 });
 
 test("should build oEmbed from JSON", async () => {