feat(atom): use id for entry link if it is an http URL

internal/reader/atom/atom_10_adapter.go

@@ -81,6 +81,16 @@ func (a *atom10Adapter) populateEntries(siteURL string) model.Entries {
 			}
 		}
 
+		// If the entry has no links, attempt to use its ID as a URL
+		// and if that fails, use the site URL.
+		if entry.URL == "" {
+			if urllib.IsAbsoluteURL(atomEntry.ID) {
+				entry.URL = atomEntry.ID
+			} else {
+				entry.URL = siteURL
+			}
+		}
+
 		// Populate the entry content.
 		entry.Content = atomEntry.Content.body()
 		if entry.Content == "" {

internal/reader/atom/atom_10_test.go

@@ -1837,3 +1837,31 @@ func TestParseFeedWithIconURL(t *testing.T) {
 		t.Errorf("Incorrect icon URL, got: %s", feed.IconURL)
 	}
 }
+
+func TestParseEntryWithIDAsURL(t *testing.T) {
+	data := `<?xml version="1.0" encoding="utf-8"?>
+	<feed xmlns="http://www.w3.org/2005/Atom">
+		<title>Example Feed</title>
+		<link href="http://example.org/"/>
+		<link href="http://example.org/atom" rel="self"/>
+		<entry>
+			<id>http://www.example.org/entries/1</id>
+		</entry>
+		<entry>
+			<id>mailto:john.doe@example.org</id>
+		</entry>
+	</feed>`
+
+	feed, err := Parse("https://example.org/", bytes.NewReader([]byte(data)), "10")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if feed.Entries[0].URL != "http://www.example.org/entries/1" {
+		t.Errorf("Incorrect entry URL, got: %s", feed.Entries[0].URL)
+	}
+
+	if feed.Entries[1].URL != "http://example.org/" {
+		t.Errorf("Incorrect entry URL, got: %s", feed.Entries[1].URL)
+	}
+}