Make error output in handlebars render error more verbose

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

1 files changed, 16 insertions, 2 deletions

diff --git a/lib/etc/libimaginteraction/src/format.rs b/lib/etc/libimaginteraction/src/format.rs
index e839e85f..a21294ad 100644
--- a/lib/etc/libimaginteraction/src/format.rs
+++ b/lib/etc/libimaginteraction/src/format.rs
@@ -152,9 +152,23 @@ impl HelperDef for StrikethroughHelper {
 }
 
 fn param_to_number(idx: usize, h: &Helper) -> Result<u64, RenderError> {
-    match *h.param(idx).ok_or_else(|| RenderError::new("Too few arguments"))?.value() {
+    fn typenameof(v: &Value) -> String {
+        match *v {
+            Value::Null      => "Null",
+            Value::Bool(_)   => "Bool",
+            Value::Number(_) => "Number",
+            Value::String(_) => "String",
+            Value::Array(_)  => "Array",
+            Value::Object(_) => "Object",
+        }.to_owned()
+    }
+
+    match h.param(idx).ok_or_else(|| RenderError::new("Too few arguments"))?.value() {
         Value::Number(ref num) => num.as_u64().ok_or_else(|| RenderError::new("Number cannot be parsed")),
-        _ => Err(RenderError::new("Type error: First argument should be a number")),
+        other => {
+            let msg = format!("Type error: First argument should be a number, but is {} -> {:?}", typenameof(other), serde_json::to_string(other));
+            Err(RenderError::new(msg))
+        },
     }
 }