Handle text/html mime type in content->type

The type attribute on a content element is not expected to contain a
mime type (the spec only defines 'text','html','xhtml').

The scattered feed specifies html content as a mime-type, which isn't
correct but we might as well work around this and avoid a parser panic.

feed-rs/fixture/atom/atom_scattered.xml

@@ -0,0 +1,18 @@
+
+<?xml version="1.0" encoding="UTF-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en">
+    <title>Scattered Thoughts</title>
+    <link href="https://www.scattered-thoughts.net/atom.xml" rel="self" type="application/atom+xml"/>
+    <link href="https://www.scattered-thoughts.net/"/>
+    <updated>2023-12-01T00:00:00+00:00</updated>
+    <author><name>Jamie Brandon</name></author>
+    <id>https://www.scattered-thoughts.net/atom.xml</id>
+    <entry xml:lang="en">
+        <title>0042: consulting lessons, there are no strings on me, buttondown, focus goof, jsfuck, 1ml</title>
+        <published>2023-12-01T00:00:00+00:00</published>
+        <updated>2023-12-01T00:00:00+00:00</updated>
+        <link href="https://www.scattered-thoughts.net/log/0042/" type="text/html" rel="alternate"/>
+        <id>https://www.scattered-thoughts.net/log/0042/</id>
+        <content type="text/html"><a href="https://www.scattered-thoughts.net/log/0042/">0042: consulting lessons, there are no strings on me</a></content>
+    </entry>
+</feed>

feed-rs/src/parser/atom/mod.rs

@@ -95,7 +95,7 @@ fn handle_content<R: BufRead>(element: Element<R>) -> ParseFeedResult<Option<Con
     // from http://www.atomenabled.org/developers/syndication/#contentElement
     match content_type.as_deref() {
         // Should be handled as a text element per "In the most common case, the type attribute is either text, html, xhtml, in which case the content element is defined identically to other text constructs"
-        Some("text") | Some("html") | Some("xhtml") | None => {
+        Some("text") | Some("html") | Some("xhtml") | Some("text/html") | None => {
             handle_text(element)?
                 .map(|text| {
                     let mut content = Content::default();
@@ -283,7 +283,7 @@ pub(crate) fn handle_text<R: BufRead>(element: Element<R>) -> ParseFeedResult<Op
 
     let mime = match type_attr {
         "text" => Ok(mime::TEXT_PLAIN),
-        "html" | "xhtml" => Ok(mime::TEXT_HTML),
+        "html" | "xhtml" | "text/html" => Ok(mime::TEXT_HTML),
 
         // Unknown content type
         _ => Err(ParseFeedError::ParseError(ParseErrorKind::UnknownMimeType(type_attr.into()))),

feed-rs/src/parser/atom/tests.rs

@@ -542,3 +542,18 @@ fn test_reddit() {
     let media_obj = &entry.media[0];
     assert_eq!(media_obj, &expected);
 }
+
+// Handle text/html specified as a mime type on content
+#[test]
+fn test_scattered() {
+    let test_data = test::fixture_as_string("atom/atom_scattered.xml");
+    let actual = parser::parse(test_data.as_bytes()).unwrap().id("");
+    assert!(actual.entries[0]
+        .content
+        .as_ref()
+        .unwrap()
+        .body
+        .as_ref()
+        .unwrap()
+        .contains("there are no strings on me"));
+}