don't hard-code available ftl languages

Instead of trying to define which languages we support, just check
if an appropriate folder is available on disk. This allows users
to drop their own translations into the locale folder and have things
just work.

rslib/src/i18n/mod.rs

@@ -2,15 +2,15 @@
 // License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 
 use fluent::{FluentArgs, FluentBundle, FluentResource};
-use log::error;
+use log::{error, warn};
 use std::borrow::Cow;
 use std::fs;
 use std::path::{Path, PathBuf};
+use std::sync::{Arc, Mutex};
 use unic_langid::LanguageIdentifier;
 
-pub use fluent::fluent_args as tr_args;
-
 pub use crate::backend_proto::StringsGroup;
+pub use fluent::fluent_args as tr_args;
 
 /// Helper for creating args with &strs
 #[macro_export]
@@ -25,38 +25,29 @@ macro_rules! tr_strs {
         }
     };
 }
-use std::sync::{Arc, Mutex};
 pub use tr_strs;
 
-/// All languages we (currently) support, excluding the fallback
-/// English.
-#[derive(Debug, PartialEq, Clone, Copy)]
-pub enum LanguageDialect {
-    Japanese,
-    ChineseMainland,
-    ChineseTaiwan,
-}
-
-fn lang_dialect(lang: LanguageIdentifier) -> Option<LanguageDialect> {
-    use LanguageDialect as L;
-    Some(match lang.get_language() {
-        "ja" => L::Japanese,
-        "zh" => match lang.get_region() {
-            Some("TW") => L::ChineseTaiwan,
-            _ => L::ChineseMainland,
-        },
-        _ => return None,
-    })
-}
-
-fn dialect_file_locale(dialect: LanguageDialect) -> &'static str {
-    match dialect {
-        LanguageDialect::Japanese => "ja",
-        LanguageDialect::ChineseMainland => "zh",
-        LanguageDialect::ChineseTaiwan => todo!(),
+/// The folder containing ftl files for the provided language.
+/// If a fully qualified folder exists (eg, en_GB), return that.
+/// Otherwise, try the language alone (eg en).
+/// If neither folder exists, return None.
+fn lang_folder(lang: LanguageIdentifier, ftl_folder: &Path) -> Option<PathBuf> {
+    if let Some(region) = lang.get_region() {
+        let path = ftl_folder.join(format!("{}_{}", lang.get_language(), region));
+        if fs::metadata(&path).is_ok() {
+            return Some(path);
+        }
+    }
+    let path = ftl_folder.join(lang.get_language());
+    if fs::metadata(&path).is_ok() {
+        Some(path)
+    } else {
+        None
     }
 }
 
+/// Get the fallback/English resource text for the given group.
+/// These are embedded in the binary.
 fn ftl_fallback_for_group(group: StringsGroup) -> String {
     match group {
         StringsGroup::Other => "",
@@ -68,27 +59,25 @@ fn ftl_fallback_for_group(group: StringsGroup) -> String {
     .to_string()
 }
 
-fn localized_ftl_for_group(
-    dialect: LanguageDialect,
-    group: StringsGroup,
-    locales: &Path,
-) -> Option<String> {
-    let path = locales
-        .join(dialect_file_locale(dialect))
-        .join(match group {
-            StringsGroup::Other => "",
-            StringsGroup::Test => "test.ftl",
-            StringsGroup::MediaCheck => "media-check.ftl",
-            StringsGroup::CardTemplates => "card-template-rendering.ftl",
-            StringsGroup::Sync => "sync.ftl",
-        });
+/// Get the resource text for the given group in the given language folder.
+/// If the file can't be read, returns None.
+fn localized_ftl_for_group(group: StringsGroup, lang_ftl_folder: &Path) -> Option<String> {
+    let path = lang_ftl_folder.join(match group {
+        StringsGroup::Other => "",
+        StringsGroup::Test => "test.ftl",
+        StringsGroup::MediaCheck => "media-check.ftl",
+        StringsGroup::CardTemplates => "card-template-rendering.ftl",
+        StringsGroup::Sync => "sync.ftl",
+    });
     fs::read_to_string(&path)
         .map_err(|e| {
-            error!("Unable to read translation file: {:?}: {}", path, e);
+            warn!("Unable to read translation file: {:?}: {}", path, e);
         })
         .ok()
 }
 
+/// Parse resource text into an AST for inclusion in a bundle.
+/// Returns None if the text contains errors.
 fn get_bundle(
     text: String,
     locales: &[LanguageIdentifier],
@@ -116,14 +105,15 @@ pub struct I18n {
 }
 
 impl I18n {
-    pub fn new<S: AsRef<str>, P: Into<PathBuf>>(locale_codes: &[S], locale_folder: P) -> Self {
+    pub fn new<S: AsRef<str>, P: Into<PathBuf>>(locale_codes: &[S], ftl_folder: P) -> Self {
         let mut langs = vec![];
         let mut supported = vec![];
+        let ftl_folder = ftl_folder.into();
         for code in locale_codes {
-            if let Ok(ident) = code.as_ref().parse::<LanguageIdentifier>() {
-                langs.push(ident.clone());
-                if let Some(dialect) = lang_dialect(ident) {
-                    supported.push(dialect)
+            if let Ok(lang) = code.as_ref().parse::<LanguageIdentifier>() {
+                langs.push(lang.clone());
+                if let Some(path) = lang_folder(lang, &ftl_folder) {
+                    supported.push(path);
                 }
             }
         }
@@ -133,29 +123,22 @@ impl I18n {
         Self {
             inner: Arc::new(Mutex::new(I18nInner {
                 langs,
-                supported,
-                locale_folder: locale_folder.into(),
+                available_ftl_folders: supported,
             })),
         }
     }
 
     pub fn get(&self, group: StringsGroup) -> I18nCategory {
         let inner = self.inner.lock().unwrap();
-        I18nCategory::new(
-            &*inner.langs,
-            &*inner.supported,
-            group,
-            &inner.locale_folder,
-        )
+        I18nCategory::new(&*inner.langs, &*inner.available_ftl_folders, group)
     }
 }
 
 struct I18nInner {
-    // language identifiers, used for date/time rendering
+    // all preferred languages of the user, used for date/time processing
     langs: Vec<LanguageIdentifier>,
-    // languages supported by us
-    supported: Vec<LanguageDialect>,
-    locale_folder: PathBuf,
+    // the available ftl folder subset of the user's preferred languages
+    available_ftl_folders: Vec<PathBuf>,
 }
 
 pub struct I18nCategory {
@@ -165,22 +148,17 @@ pub struct I18nCategory {
 }
 
 impl I18nCategory {
-    pub fn new(
-        langs: &[LanguageIdentifier],
-        preferred: &[LanguageDialect],
-        group: StringsGroup,
-        locale_folder: &Path,
-    ) -> Self {
+    pub fn new(langs: &[LanguageIdentifier], preferred: &[PathBuf], group: StringsGroup) -> Self {
         let mut bundles = Vec::with_capacity(preferred.len() + 1);
-        for dialect in preferred {
-            if let Some(text) = localized_ftl_for_group(*dialect, group, locale_folder) {
+        for ftl_folder in preferred {
+            if let Some(text) = localized_ftl_for_group(group, ftl_folder) {
                 if let Some(mut bundle) = get_bundle(text, langs) {
                     if cfg!(test) {
                         bundle.set_use_isolating(false);
                     }
                     bundles.push(bundle);
                 } else {
-                    error!("Failed to create bundle for {:?} {:?}", dialect, group);
+                    error!("Failed to create bundle for {:?} {:?}", ftl_folder, group);
                 }
             }
         }
@@ -234,27 +212,9 @@ impl I18nCategory {
 
 #[cfg(test)]
 mod test {
-    use crate::i18n::{dialect_file_locale, lang_dialect, StringsGroup};
-    use crate::i18n::{tr_args, I18n, LanguageDialect};
+    use crate::i18n::StringsGroup;
+    use crate::i18n::{tr_args, I18n};
     use std::path::PathBuf;
-    use unic_langid::LanguageIdentifier;
-
-    #[test]
-    fn dialect() {
-        use LanguageDialect as L;
-        let mut ident: LanguageIdentifier = "en-US".parse().unwrap();
-        assert_eq!(lang_dialect(ident), None);
-        ident = "ja_JP".parse().unwrap();
-        assert_eq!(lang_dialect(ident), Some(L::Japanese));
-        ident = "zh".parse().unwrap();
-        assert_eq!(lang_dialect(ident), Some(L::ChineseMainland));
-        ident = "zh-TW".parse().unwrap();
-        assert_eq!(lang_dialect(ident), Some(L::ChineseTaiwan));
-
-        assert_eq!(dialect_file_locale(L::Japanese), "ja");
-        assert_eq!(dialect_file_locale(L::ChineseMainland), "zh");
-        //        assert_eq!(dialect_file_locale(L::Other), "templates");
-    }
 
     #[test]
     fn i18n() {