From d690dd9d6872b7155a48b7853d1c092e8f084d3d Mon Sep 17 00:00:00 2001
From: Christiaan Baartse <cbaartse@leviy.com>
Date: Fri, 22 May 2020 11:34:03 +0200
Subject: [PATCH] Change Book.coverUrl to return null when there is no cover

CoverUrl now returns an undefined when there is no cover. However not
having a cover is expected behavior for an epub without a cover.
---
 documentation/md/API.md |  4 ++--
 src/book.js             | 21 +++++++++++----------
 test/book.js            |  2 +-
 types/book.d.ts         |  2 +-
 4 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/documentation/md/API.md b/documentation/md/API.md
index cfad86d..60a447b 100644
--- a/documentation/md/API.md
+++ b/documentation/md/API.md
@@ -134,9 +134,9 @@ Set headers request should use
 
 ### coverUrl
 
-Get the cover url
+Get the cover url if there is a cover
 
-Returns **[Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise)&lt;[string](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)>** Promise resolves with url string
+Returns **[Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise)&lt;[?string](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)&gt;** Promise resolves with maybe a url string
 
 ### getRange
 
diff --git a/src/book.js b/src/book.js
index c75c58d..f5fd332 100644
--- a/src/book.js
+++ b/src/book.js
@@ -661,19 +661,20 @@ class Book {
 
 	/**
 	 * Get the cover url
-	 * @return {Promise<string>} coverUrl
+	 * @return {Promise<?string>} coverUrl
 	 */
 	coverUrl() {
-		var retrieved = this.loaded.cover.
-			then(() => {
-				if(this.archived && this.cover) {
-					return this.archive.createUrl(this.cover);
-				}else{
-					return this.cover;
-				}
-			});
+		return this.loaded.cover.then(() => {
+			if (!this.cover) {
+				return null;
+			}
 
-		return retrieved;
+			if (this.archived) {
+				return this.archive.createUrl(this.cover);
+			} else {
+				return this.cover;
+			}
+		});
 	}
 
 	/**
diff --git a/test/book.js b/test/book.js
index b839f56..41e2753 100644
--- a/test/book.js
+++ b/test/book.js
@@ -61,7 +61,7 @@ describe('Book', function() {
 		});
 		it('should have a empty coverUrl', async function() {
 			let coverUrl = await book.coverUrl()
-			assert.equal(coverUrl, undefined, "cover url should be undefined" );
+			assert.equal(coverUrl, null, "cover url should be null" );
 		});
 	});
 });
diff --git a/types/book.d.ts b/types/book.d.ts
index 6f4a2ee..f1326b2 100644
--- a/types/book.d.ts
+++ b/types/book.d.ts
@@ -65,7 +65,7 @@ export default class Book {
 
     canonical(path: string): string;
 
-    coverUrl(): Promise<string>;
+    coverUrl(): Promise<string | null>;
 
     destroy(): void;