1 files changed, 71 insertions, 0 deletions
diff --git a/third_party/rust/fluent-fallback/src/errors.rs b/third_party/rust/fluent-fallback/src/errors.rs
new file mode 100644
index 0000000000..9170fb1cb9
--- /dev/null
+++ b/third_party/rust/fluent-fallback/src/errors.rs
@@ -0,0 +1,71 @@
+use fluent_bundle::FluentError;
+use std::error::Error;
+use unic_langid::LanguageIdentifier;
+
+#[derive(Debug, PartialEq)]
+pub enum LocalizationError {
+    Bundle {
+        error: FluentError,
+    },
+    Resolver {
+        id: String,
+        locale: LanguageIdentifier,
+        errors: Vec<FluentError>,
+    },
+    MissingMessage {
+        id: String,
+        locale: Option<LanguageIdentifier>,
+    },
+    MissingValue {
+        id: String,
+        locale: Option<LanguageIdentifier>,
+    },
+    SyncRequestInAsyncMode,
+}
+
+impl From<FluentError> for LocalizationError {
+    fn from(error: FluentError) -> Self {
+        Self::Bundle { error }
+    }
+}
+
+impl std::fmt::Display for LocalizationError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::Bundle { error } => write!(f, "[fluent][bundle] error: {}", error),
+            Self::Resolver { id, locale, errors } => {
+                let errors: Vec<String> = errors.iter().map(|err| err.to_string()).collect();
+                write!(
+                    f,
+                    "[fluent][resolver] errors in {}/{}: {}",
+                    locale,
+                    id,
+                    errors.join(", ")
+                )
+            }
+            Self::MissingMessage {
+                id,
+                locale: Some(locale),
+            } => write!(f, "[fluent] Missing message in locale {}: {}", locale, id),
+            Self::MissingMessage { id, locale: None } => {
+                write!(f, "[fluent] Couldn't find a message: {}", id)
+            }
+            Self::MissingValue {
+                id,
+                locale: Some(locale),
+            } => write!(
+                f,
+                "[fluent] Message has no value in locale {}: {}",
+                locale, id
+            ),
+            Self::MissingValue { id, locale: None } => {
+                write!(f, "[fluent] Couldn't find a message with value: {}", id)
+            }
+            Self::SyncRequestInAsyncMode => {
+                write!(f, "Triggered synchronous format while in async mode")
+            }
+        }
+    }
+}
+
+impl Error for LocalizationError {}