Fix #59

src/error.rs

@@ -176,6 +176,10 @@ impl Error {
         })
     }
 
+    pub(crate) fn unexpected_data(value: &str) -> Self {
+        Self::custom(format!("Unexpected data in the line: {:?}", value))
+    }
+
     // third party crates:
     #[cfg(feature = "chrono")]
     pub(crate) fn chrono(source: chrono::format::ParseError) -> Self {

src/line.rs

@@ -92,6 +92,8 @@ impl<'a> TryFrom<&'a str> for Tag<'a> {
             TryFrom::try_from(input).map(Self::ExtInf)
         } else if input.starts_with(tags::ExtXByteRange::PREFIX) {
             TryFrom::try_from(input).map(Self::ExtXByteRange)
+        } else if input.starts_with(tags::ExtXDiscontinuitySequence::PREFIX) {
+            TryFrom::try_from(input).map(Self::ExtXDiscontinuitySequence)
         } else if input.starts_with(tags::ExtXDiscontinuity::PREFIX) {
             TryFrom::try_from(input).map(Self::ExtXDiscontinuity)
         } else if input.starts_with(tags::ExtXKey::PREFIX) {
@@ -106,8 +108,6 @@ impl<'a> TryFrom<&'a str> for Tag<'a> {
             TryFrom::try_from(input).map(Self::ExtXDateRange)
         } else if input.starts_with(tags::ExtXMediaSequence::PREFIX) {
             TryFrom::try_from(input).map(Self::ExtXMediaSequence)
-        } else if input.starts_with(tags::ExtXDiscontinuitySequence::PREFIX) {
-            TryFrom::try_from(input).map(Self::ExtXDiscontinuitySequence)
         } else if input.starts_with(tags::ExtXEndList::PREFIX) {
             TryFrom::try_from(input).map(Self::ExtXEndList)
         } else if input.starts_with(PlaylistType::PREFIX) {

src/media_playlist.rs

@@ -659,12 +659,16 @@ fn parse_media_playlist<'a>(
                         builder.media_sequence(t.0);
                     }
                     Tag::ExtXDiscontinuitySequence(t) => {
-                        if segments.is_empty() {
-                            return Err(Error::invalid_input());
+                        // this tag must appear before the first MediaSegment in the playlist
+                        // https://tools.ietf.org/html/rfc8216#section-4.3.3.3
+                        if !segments.is_empty() {
+                            return Err(Error::custom("discontinuity sequence tag must appear before the first media segment in the playlist"));
                         }
 
+                        // this tag must appear before any ExtXDiscontinuity tag
+                        // https://tools.ietf.org/html/rfc8216#section-4.3.3.3
                         if has_discontinuity_tag {
-                            return Err(Error::invalid_input());
+                            return Err(Error::custom("discontinuity sequence tag must appear before any `ExtXDiscontinuity` tag"));
                         }
 
                         builder.discontinuity_sequence(t.0);

src/tags/media_segment/discontinuity.rs

@@ -2,7 +2,6 @@ use std::convert::TryFrom;
 use std::fmt;
 
 use crate::types::ProtocolVersion;
-use crate::utils::tag;
 use crate::{Error, RequiredVersion};
 
 /// The `ExtXDiscontinuity` tag indicates a discontinuity between the
@@ -27,8 +26,13 @@ impl TryFrom<&str> for ExtXDiscontinuity {
     type Error = Error;
 
     fn try_from(input: &str) -> Result<Self, Self::Error> {
-        tag(input, Self::PREFIX)?;
-        Ok(Self)
+        // the parser assumes that only a single line is passed as input,
+        // which should be "#EXT-X-DISCONTINUITY"
+        if input == Self::PREFIX {
+            Ok(Self)
+        } else {
+            Err(Error::unexpected_data(input))
+        }
     }
 }
 
@@ -50,7 +54,9 @@ mod test {
         assert_eq!(
             ExtXDiscontinuity,
             ExtXDiscontinuity::try_from("#EXT-X-DISCONTINUITY").unwrap()
-        )
+        );
+
+        assert!(ExtXDiscontinuity::try_from("#EXT-X-DISCONTINUITY:0").is_err());
     }
 
     #[test]

tests/issues/issue_00059.rs

@@ -0,0 +1,27 @@
+// The relevant issue:
+// https://github.com/sile/hls_m3u8/issues/59
+use std::convert::TryFrom;
+
+use hls_m3u8::MediaPlaylist;
+
+use pretty_assertions::assert_eq;
+
+#[test]
+fn parse() {
+    let playlist = concat!(
+        "#EXTM3U\n",
+        "#EXT-X-DISCONTINUITY-SEQUENCE:1\n",
+        "#EXT-X-TARGETDURATION:10\n",
+        "#EXT-X-VERSION:3\n",
+        "#EXTINF:9.009,\n",
+        "http://media.example.com/first.ts\n",
+        "#EXTINF:9.009,\n",
+        "http://media.example.com/second.ts\n",
+        "#EXTINF:3.003,\n",
+        "http://media.example.com/third.ts\n",
+        "#EXT-X-ENDLIST"
+    );
+
+    let playlist = MediaPlaylist::try_from(playlist).unwrap();
+    assert_eq!(playlist.discontinuity_sequence, 1);
+}