Add the isPermaLink attribute to guid in RSS (#107)

Adds the optional attribute from the `guid` RSS spec:
https://www.rssboard.org/rss-specification#ltguidgtSubelementOfLtitemgt

This is a breaking change to the `RssItem` struct as `Guid` is now a
struct, not a string.

- Related Issue go-gitea/gitea#28734
- Closes #78
- Closes #109 

Signed-off-by: Yarden Shoham <git@yardenshoham.com>

Author: yardenshoham

consume_test.go

@@ -46,7 +46,7 @@ var testRssFeedXML = RssFeedXml{
 				Category:    "",
 				Comments:    "",
 				Enclosure:   (*RssEnclosure)(nil),
-				Guid:        "http://example.com/test/1540941720",
+				Guid:        &RssGuid{XMLName: xml.Name{Local: "guid"}, Id: "http://example.com/test/1540941720", IsPermaLink: "true"},
 				PubDate:     "Tue, 30 Oct 2018 23:22:00 GMT",
 				Source:      "",
 			},
@@ -60,7 +60,7 @@ var testRssFeedXML = RssFeedXml{
 				Category:    "",
 				Comments:    "",
 				Enclosure:   (*RssEnclosure)(nil),
-				Guid:        "http://example.com/test/1540941660",
+				Guid:        &RssGuid{XMLName: xml.Name{Local: "guid"}, Id: "http://example.com/test/1540941660", IsPermaLink: "true"},
 				PubDate:     "Tue, 30 Oct 2018 23:21:00 GMT",
 				Source:      "",
 			},
@@ -74,7 +74,7 @@ var testRssFeedXML = RssFeedXml{
 				Category:    "",
 				Comments:    "",
 				Enclosure:   (*RssEnclosure)(nil),
-				Guid:        "http://example.com/test/1540941600",
+				Guid:        &RssGuid{XMLName: xml.Name{Local: "guid"}, Id: "http://example.com/test/1540941600", IsPermaLink: "true"},
 				PubDate:     "Tue, 30 Oct 2018 23:20:00 GMT",
 				Source:      "",
 			},
@@ -88,7 +88,7 @@ var testRssFeedXML = RssFeedXml{
 				Category:    "",
 				Comments:    "",
 				Enclosure:   (*RssEnclosure)(nil),
-				Guid:        "http://example.com/test/1540941540",
+				Guid:        &RssGuid{XMLName: xml.Name{Local: "guid"}, Id: "http://example.com/test/1540941540", IsPermaLink: "true"},
 				PubDate:     "Tue, 30 Oct 2018 23:19:00 GMT",
 				Source:      "",
 			},
@@ -102,7 +102,7 @@ var testRssFeedXML = RssFeedXml{
 				Category:    "",
 				Comments:    "",
 				Enclosure:   (*RssEnclosure)(nil),
-				Guid:        "http://example.com/test/1540941480",
+				Guid:        &RssGuid{XMLName: xml.Name{Local: "guid"}, Id: "http://example.com/test/1540941480", IsPermaLink: "true"},
 				PubDate:     "Tue, 30 Oct 2018 23:18:00 GMT",
 				Source:      "",
 			},
@@ -116,7 +116,7 @@ var testRssFeedXML = RssFeedXml{
 				Category:    "",
 				Comments:    "",
 				Enclosure:   (*RssEnclosure)(nil),
-				Guid:        "http://example.com/test/1540941420",
+				Guid:        &RssGuid{XMLName: xml.Name{Local: "guid"}, Id: "http://example.com/test/1540941420", IsPermaLink: "true"},
 				PubDate:     "Tue, 30 Oct 2018 23:17:00 GMT",
 				Source:      "",
 			},
@@ -130,7 +130,7 @@ var testRssFeedXML = RssFeedXml{
 				Category:    "",
 				Comments:    "",
 				Enclosure:   (*RssEnclosure)(nil),
-				Guid:        "http://example.com/test/1540941360",
+				Guid:        &RssGuid{XMLName: xml.Name{Local: "guid"}, Id: "http://example.com/test/1540941360", IsPermaLink: "true"},
 				PubDate:     "Tue, 30 Oct 2018 23:16:00 GMT",
 				Source:      "",
 			},
@@ -144,7 +144,7 @@ var testRssFeedXML = RssFeedXml{
 				Category:    "",
 				Comments:    "",
 				Enclosure:   (*RssEnclosure)(nil),
-				Guid:        "http://example.com/test/1540941300",
+				Guid:        &RssGuid{XMLName: xml.Name{Local: "guid"}, Id: "http://example.com/test/1540941300", IsPermaLink: "true"},
 				PubDate:     "Tue, 30 Oct 2018 23:15:00 GMT",
 				Source:      "",
 			},
@@ -158,7 +158,7 @@ var testRssFeedXML = RssFeedXml{
 				Category:    "",
 				Comments:    "",
 				Enclosure:   (*RssEnclosure)(nil),
-				Guid:        "http://example.com/test/1540941240",
+				Guid:        &RssGuid{XMLName: xml.Name{Local: "guid"}, Id: "http://example.com/test/1540941240", IsPermaLink: "true"},
 				PubDate:     "Tue, 30 Oct 2018 23:14:00 GMT",
 				Source:      "",
 			},
@@ -172,7 +172,7 @@ var testRssFeedXML = RssFeedXml{
 				Category:    "",
 				Comments:    "",
 				Enclosure:   (*RssEnclosure)(nil),
-				Guid:        "http://example.com/test/1540941180",
+				Guid:        &RssGuid{XMLName: xml.Name{Local: "guid"}, Id: "http://example.com/test/1540941180", IsPermaLink: "true"},
 				PubDate:     "Tue, 30 Oct 2018 23:13:00 GMT",
 				Source:      "",
 			},

feed.go

@@ -32,6 +32,7 @@ type Item struct {
 	Author      *Author
 	Description string // used as description in rss, summary in atom
 	Id          string // used as guid in rss, id in atom
+	IsPermaLink string // an optional parameter for guid in rss
 	Updated     time.Time
 	Created     time.Time
 	Enclosure   *Enclosure

rss.go

@@ -74,9 +74,9 @@ type RssItem struct {
 	Category    string `xml:"category,omitempty"`
 	Comments    string `xml:"comments,omitempty"`
 	Enclosure   *RssEnclosure
-	Guid        string `xml:"guid,omitempty"`    // Id used
-	PubDate     string `xml:"pubDate,omitempty"` // created or updated
-	Source      string `xml:"source,omitempty"`
+	Guid        *RssGuid // Id used
+	PubDate     string   `xml:"pubDate,omitempty"` // created or updated
+	Source      string   `xml:"source,omitempty"`
 }
 
 type RssEnclosure struct {
@@ -87,6 +87,13 @@ type RssEnclosure struct {
 	Type    string   `xml:"type,attr"`
 }
 
+type RssGuid struct {
+	//RSS 2.0 <guid isPermaLink="true">http://inessential.com/2002/09/01.php#a2</guid>
+	XMLName     xml.Name `xml:"guid"`
+	Id          string   `xml:",chardata"`
+	IsPermaLink string   `xml:"isPermaLink,attr,omitempty"` // "true", "false", or an empty string
+}
+
 type Rss struct {
 	*Feed
 }
@@ -96,9 +103,11 @@ func newRssItem(i *Item) *RssItem {
 	item := &RssItem{
 		Title:       i.Title,
 		Description: i.Description,
-		Guid:        i.Id,
 		PubDate:     anyTimeFormat(time.RFC1123Z, i.Created, i.Updated),
 	}
+	if i.Id != "" {
+		item.Guid = &RssGuid{Id: i.Id, IsPermaLink: i.IsPermaLink}
+	}
 	if i.Link != nil {
 		item.Link = i.Link.Href
 	}