Fix handling of content:encoded

PR mmcdole#220 introduced a failing test for detecting images in the "content"
element. It should instead be testing the "content:encoded" element. But
that uncovered an issue with how extensions were being detected (the
"content" namespace was being detected as an extension namespace).

As a more robust way of checking for the "content" namespace, this PR
exposes `shared.PrefixForNamspace()` as a public function so it can be
used in the rss parser. This provides a solution to PR mmcdole#211 (and
includes @JLugagne's test case from that PR).

Once the fixes to xml:base handling in mmcdole#222 are merged, this should fix
the remaining failing test reported in mmcdole#210.

internal/shared/extparser.go

@@ -12,18 +12,15 @@ import (
 // non empty prefix)
 func IsExtension(p *xpp.XMLPullParser) bool {
 	space := strings.TrimSpace(p.Space)
-	if prefix, ok := p.Spaces[space]; ok {
-		return !(prefix == "" || prefix == "rss" || prefix == "rdf" || prefix == "content")
-	}
-
-	return p.Space != ""
+	prefix := PrefixForNamespace(space, p)
+	return !(prefix == "" || prefix == "rss" || prefix == "rdf" || prefix == "content")
 }
 
 // ParseExtension parses the current element of the
 // XMLPullParser as an extension element and updates
 // the extension map
 func ParseExtension(fe ext.Extensions, p *xpp.XMLPullParser) (ext.Extensions, error) {
-	prefix := prefixForNamespace(p.Space, p)
+	prefix := PrefixForNamespace(p.Space, p)
 
 	result, err := parseExtensionElement(p)
 	if err != nil {
@@ -93,7 +90,7 @@ func parseExtensionElement(p *xpp.XMLPullParser) (e ext.Extension, err error) {
 	return e, nil
 }
 
-func prefixForNamespace(space string, p *xpp.XMLPullParser) string {
+func PrefixForNamespace(space string, p *xpp.XMLPullParser) string {
 	// First we check if the global namespace map
 	// contains an entry for this namespace/prefix.
 	// This way we can use the canonical prefix for this

rss/parser.go

@@ -357,7 +357,8 @@ func (rp *Parser) parseItem(p *xpp.XMLPullParser) (item *Item, err error) {
 				item.Description = result
 			} else if name == "encoded" {
 				space := strings.TrimSpace(p.Space)
-				if prefix, ok := p.Spaces[space]; ok && prefix == "content" {
+				prefix := shared.PrefixForNamespace(space, p)
+				if prefix == "content" {
 					result, err := shared.ParseText(p)
 					if err != nil {
 						return nil, err

testdata/parser/rss/rss_channel_item_content_encoded.json

@@ -0,0 +1,8 @@
+{
+    "items": [
+        {
+            "content": "Item Description"
+        }
+    ],
+    "version": "2.0"
+}

testdata/parser/rss/rss_channel_item_content_encoded.xml

@@ -0,0 +1,10 @@
+<!--
+Description: rss item content encoded 
+-->
+<rss version="2.0" xmlns:content="http://purl.org/rss/1.0/modules/content/">
+    <channel>
+      <item>
+        <content:encoded xmlns="http://purl.org/rss/1.0/modules/content/">Item Description</content:encoded>
+      </item>
+    </channel>
+  </rss>

testdata/translator/rss/feed_item_image_-_rss_channel_item_content.xml

@@ -4,7 +4,7 @@ Description: item image from content
 <rss version="0.91">
   <channel>
     <item>
-      <content><![CDATA[<img src="http://example.com/content.png">]]></content>
+      <content:encoded><![CDATA[<img src="http://example.com/content.png">]]></content:encoded>
     </item>
   </channel>
 </rss>