id3v2: Use "XXX" if the actual language is unknown

src/id3/v2/frame/mod.rs

@@ -20,6 +20,14 @@ use crate::id3::v2::items::popularimeter::Popularimeter;
 use std::convert::{TryFrom, TryInto};
 use std::hash::{Hash, Hasher};
 
+// <https://mutagen-specs.readthedocs.io/en/latest/id3/id3v2.4.0-structure.html>
+//
+// > The three byte language field, present in several frames, is used to describe
+// > the language of the frame’s content, according to ISO-639-2 [ISO-639-2].
+// > The language should be represented in lower case. If the language is not known
+// > the string “XXX” should be used.
+pub(super) const UNKNOWN_LANGUAGE: [u8; 3] = *b"XXX";
+
 // TODO: Messy module, rough conversions
 
 /// Represents an `ID3v2` frame
@@ -270,20 +278,19 @@ impl From<TagItem> for Option<Frame<'static>> {
 let value;
 match input.key().try_into().map(FrameID::into_owned) {
 Ok(id) => {
-// We make the VERY bold assumption the language is English
 value = match (&id, input.item_value) {
 (FrameID::Valid(ref s), ItemValue::Text(text)) if s == "COMM" => {
 FrameValue::Comment(LanguageFrame {
 encoding: TextEncoding::UTF8,
-language: *b"eng",
+language: UNKNOWN_LANGUAGE,
 description: String::new(),
 content: text,
 })
 },
 (FrameID::Valid(ref s), ItemValue::Text(text)) if s == "USLT" => {
 FrameValue::UnSyncText(LanguageFrame {
 encoding: TextEncoding::UTF8,
-language: *b"eng",
+language: UNKNOWN_LANGUAGE,
 description: String::new(),
 content: text,
 })
@@ -383,13 +390,13 @@ impl<'a> TryFrom<&'a TagItem> for FrameRef<'a> {
 value: Cow::Owned(match (id, tag_item.value()) {
 ("COMM", ItemValue::Text(text)) => FrameValue::Comment(LanguageFrame {
 encoding: TextEncoding::UTF8,
-language: *b"eng",
+language: UNKNOWN_LANGUAGE,
 description: String::new(),
 content: text.clone(),
 }),
 ("USLT", ItemValue::Text(text)) => FrameValue::UnSyncText(LanguageFrame {
 encoding: TextEncoding::UTF8,
-language: *b"eng",
+language: UNKNOWN_LANGUAGE,
 description: String::new(),
 content: text.clone(),
 }),

src/id3/v2/tag.rs

@@ -1,6 +1,6 @@
 use super::flags::ID3v2TagFlags;
 use super::frame::id::FrameID;
-use super::frame::{Frame, FrameFlags, FrameValue};
+use super::frame::{Frame, FrameFlags, FrameValue, UNKNOWN_LANGUAGE};
 use super::ID3v2Version;
 use crate::error::{LoftyError, Result};
 use crate::id3::v2::frame::FrameRef;
@@ -62,7 +62,7 @@ macro_rules! impl_accessor {
 ///
 /// * [`ItemKey::Comment`](crate::ItemKey::Comment) and [`ItemKey::Lyrics`](crate::ItemKey::Lyrics) - Unlike a normal text frame, these require a [`LanguageFrame`].
 /// An attempt is made to create this information, but it may be incorrect.
-/// * `language` - Assumed to be "eng"
+/// * `language` - Unknown and set to "XXX"
 /// * `description` - Left empty, which is invalid if there are more than one of these frames. These frames can only be identified
 /// by their descriptions, and as such they are expected to be unique for each.
 /// * [`ItemKey::Unknown("WXXX" | "TXXX")`](crate::ItemKey::Unknown) - These frames are also identified by their descriptions.
@@ -422,7 +422,7 @@ impl Accessor for ID3v2Tag {
 id: FrameID::Valid(Cow::Borrowed("COMM")),
 value: FrameValue::Comment(LanguageFrame {
 encoding: TextEncoding::UTF8,
-language: *b"eng",
+language: UNKNOWN_LANGUAGE,
 description: String::new(),
 content: value,
 }),