Handle RSS entries with only a GUID permalink

reader/rss/parser_test.go

@@ -95,6 +95,10 @@ func TestParseRss2Sample(t *testing.T) {
 	if feed.Entries[0].Content != `How do Americans get ready to work with Russians aboard the International Space Station? They take a crash course in culture, language and protocol at Russia's <a href="http://howe.iki.rssi.ru/GCTC/gctc_e.htm">Star City</a>.` {
 		t.Errorf("Incorrect entry content, got: %s", feed.Entries[0].Content)
 	}
+
+	if feed.Entries[1].URL != "http://liftoff.msfc.nasa.gov/2003/05/30.html#item572" {
+		t.Errorf("Incorrect entry URL, got: %s", feed.Entries[1].URL)
+	}
 }
 
 func TestParseFeedWithoutTitle(t *testing.T) {
@@ -230,6 +234,34 @@ func TestParseEntryWithoutLink(t *testing.T) {
 	}
 }
 
+func TestParseEntryWithOnlyGuidPermalink(t *testing.T) {
+	data := `<?xml version="1.0" encoding="utf-8"?>
+		<rss version="2.0">
+		<channel>
+			<link>https://example.org/</link>
+			<item>
+				<guid isPermaLink="true">https://example.org/some-article.html</guid>
+			</item>
+			<item>
+				<guid>https://example.org/another-article.html</guid>
+			</item>
+		</channel>
+		</rss>`
+
+	feed, err := Parse("https://example.org/", bytes.NewBufferString(data))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if feed.Entries[0].URL != "https://example.org/some-article.html" {
+		t.Errorf("Incorrect entry link, got: %s", feed.Entries[0].URL)
+	}
+
+	if feed.Entries[1].URL != "https://example.org/another-article.html" {
+		t.Errorf("Incorrect entry link, got: %s", feed.Entries[1].URL)
+	}
+}
+
 func TestParseEntryWithAtomLink(t *testing.T) {
 	data := `<?xml version="1.0" encoding="utf-8"?>
 		<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">

reader/rss/rss.go

@@ -118,6 +118,12 @@ func (r rssFeed) feedAuthor() string {
 	return sanitizer.StripTags(strings.TrimSpace(author))
 }
 
+type rssGUID struct {
+	XMLName     xml.Name
+	Data        string `xml:",chardata"`
+	IsPermaLink string `xml:"isPermaLink,attr"`
+}
+
 type rssLink struct {
 	XMLName xml.Name
 	Data    string `xml:",chardata"`
@@ -159,7 +165,7 @@ func (enclosure *rssEnclosure) Size() int64 {
 }
 
 type rssItem struct {
-	GUID           string           `xml:"guid"`
+	GUID           rssGUID          `xml:"guid"`
 	Title          []rssTitle       `xml:"title"`
 	Links          []rssLink        `xml:"link"`
 	Description    string           `xml:"description"`
@@ -237,7 +243,7 @@ func (r *rssItem) entryAuthor() string {
 }
 
 func (r *rssItem) entryHash() string {
-	for _, value := range []string{r.GUID, r.entryURL()} {
+	for _, value := range []string{r.GUID.Data, r.entryURL()} {
 		if value != "" {
 			return crypto.Hash(value)
 		}
@@ -291,6 +297,13 @@ func (r *rssItem) entryURL() string {
 		}
 	}
 
+	// Specs: https://cyber.harvard.edu/rss/rss.html#ltguidgtSubelementOfLtitemgt
+	// isPermaLink is optional, its default value is true.
+	// If its value is false, the guid may not be assumed to be a url, or a url to anything in particular.
+	if r.GUID.IsPermaLink == "true" || r.GUID.IsPermaLink == "" {
+		return strings.TrimSpace(r.GUID.Data)
+	}
+
 	return ""
 }