print original code if external formatter raised an error

dprint_plugin/src/lib.rs

@@ -95,7 +95,9 @@ impl SyncPluginHandler<FormatOptions> for MarkupFmtPluginHandler {
         match format_result {
             Ok(code) => Ok(Some(code.into_bytes())),
             Err(FormatError::Syntax(err)) => Err(err.into()),
-            Err(FormatError::External(err)) => Err(err),
+            Err(FormatError::External(err, code)) => Err(anyhow::anyhow!(
+                "[markup_fmt] failed to format code with external formatter: `{code}`:\n{err}"
+            )),
         }
     }
 }

markup_fmt/src/ctx.rs

@@ -20,7 +20,7 @@ where
     pub(crate) in_svg: bool,
     pub(crate) indent_level: usize,
     pub(crate) external_formatter: F,
-    pub(crate) external_formatter_error: Option<E>,
+    pub(crate) external_formatter_error: Option<(E, String)>,
 }
 
 impl<'b, 's, E, F> Ctx<'b, 's, E, F>
@@ -101,7 +101,8 @@ where
                     .saturating_sub(self.indent_level)
                     .saturating_sub(2), // this is technically wrong, just workaround
             );
-            let formatted = formatted.trim_end_matches(|c: char| c.is_ascii_whitespace() || c == ';');
+            let formatted =
+                formatted.trim_end_matches(|c: char| c.is_ascii_whitespace() || c == ';');
             formatted
                 .strip_prefix("let e =")
                 .unwrap_or(formatted)
@@ -189,7 +190,7 @@ where
         match (self.external_formatter)(path, code, print_width) {
             Ok(code) => code,
             Err(e) => {
-                self.external_formatter_error = Some(e);
+                self.external_formatter_error = Some((e, code.to_owned()));
                 code.into()
             }
         }

markup_fmt/src/error.rs

@@ -89,7 +89,7 @@ pub enum FormatError<E> {
     Syntax(SyntaxError),
     /// Error from external formatter, for example,
     /// there're errors when formatting the `<script>` or `<style>` tag.
-    External(E),
+    External(E, String),
 }
 
 impl<E> fmt::Display for FormatError<E>
@@ -99,7 +99,10 @@ where
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             FormatError::Syntax(e) => e.fmt(f),
-            FormatError::External(e) => e.fmt(f),
+            FormatError::External(e, code) => write!(
+                f,
+                "failed to format code with external formatter: `{code}`:\n{e}"
+            ),
         }
     }
 }

markup_fmt/src/lib.rs

@@ -73,8 +73,8 @@ where
     };
 
     let doc = ast.doc(&mut ctx);
-    if let Some(error) = ctx.external_formatter_error {
-        return Err(FormatError::External(error));
+    if let Some((error, code)) = ctx.external_formatter_error {
+        return Err(FormatError::External(error, code));
     }
 
     Ok(tiny_pretty::print(