Only include error locations when necessary

When spans are available, locations in the message add noise.

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 - Derived impls of `FromMeta` will now error on literals, rather than silently ignoring them. [#193](https://github.com/TedDriggs/darling/pull/193)
+- Don't include property paths in compile errors when spans are available.
 
 ## v0.14.1 (April 28, 2022)
 

core/src/error/mod.rs

@@ -446,7 +446,16 @@ impl From<syn::Error> for Error {
 impl From<Error> for syn::Error {
     fn from(e: Error) -> Self {
         if e.len() == 1 {
-            syn::Error::new(e.span(), e)
+            if let Some(span) = e.explicit_span() {
+                // Don't include the location path if the error has an explicit span,
+                // since it will be redundant and isn't consistent with how rustc
+                // exposes errors.
+                syn::Error::new(span, e.kind)
+            } else {
+                // If the error's span is going to be the macro call site, include
+                // the location information to try and help the user pinpoint the issue.
+                syn::Error::new(e.span(), e)
+            }
         } else {
             let mut syn_errors = e.flatten().into_iter().map(syn::Error::from);
             let mut error = syn_errors