Allow catching of exception

Author: Sytten

src/err.rs

@@ -1,6 +1,6 @@
 use std::{error, fmt};
 
-use rquickjs::Error as JSError;
+use rquickjs::{Ctx, Error as JSError, Exception, Value};
 use serde::{de, ser};
 
 /// This type represents all possible errors that can occur when serializing or
@@ -11,6 +11,10 @@ impl Error {
     pub(crate) fn new(msg: impl Into<ErrorImpl>) -> Self {
         Error(Box::new(msg.into()))
     }
+
+    pub fn catch<'js>(self, ctx: &Ctx<'js>) -> CaughtError<'js> {
+        self.0.catch(ctx)
+    }
 }
 
 /// Alias for a `Result` with the error type `rquickjs_serde::Error`.
@@ -54,6 +58,26 @@ pub enum ErrorImpl {
     Rquickjs(JSError),
 }
 
+impl ErrorImpl {
+    pub fn catch<'js>(self, ctx: &Ctx<'js>) -> CaughtError<'js> {
+        match self {
+            ErrorImpl::Message(msg) => CaughtError::Message(msg),
+            ErrorImpl::Rquickjs(JSError::Exception) => {
+                let value = ctx.catch();
+                if let Some(ex) = value
+                    .as_object()
+                    .and_then(|x| Exception::from_object(x.clone()))
+                {
+                    CaughtError::Exception(ex)
+                } else {
+                    CaughtError::Value(value)
+                }
+            }
+            ErrorImpl::Rquickjs(e) => CaughtError::Error(e),
+        }
+    }
+}
+
 impl fmt::Display for ErrorImpl {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
@@ -74,3 +98,31 @@ impl From<JSError> for ErrorImpl {
         ErrorImpl::Rquickjs(value)
     }
 }
+
+/// An error type containing possible thrown exception values.
+#[derive(Debug)]
+pub enum CaughtError<'js> {
+    /// Error was an exception and an instance of Error
+    Exception(Exception<'js>),
+    /// Error was an exception but not an instance of Error.
+    Value(Value<'js>),
+    /// Error wasn't an exception
+    Error(JSError),
+    /// A generic error message
+    Message(String),
+}
+
+impl<'js> fmt::Display for CaughtError<'js> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            CaughtError::Error(e) => e.fmt(f),
+            CaughtError::Exception(e) => e.fmt(f),
+            CaughtError::Value(e) => {
+                writeln!(f, "Exception generated by quickjs: {e:?}")
+            }
+            CaughtError::Message(msg) => write!(f, "{msg}"),
+        }
+    }
+}
+
+impl<'js> error::Error for CaughtError<'js> {}