Don't drop internal warnings in tests

Author: camsteffen

src/test/mod.rs

@@ -630,8 +630,11 @@ fn check_files(files: Vec<PathBuf>, opt_config: &Option<PathBuf>) -> (Vec<Format
             }
             Ok(report) => reports.push(report),
             Err(err) => {
-                if let IdempotentCheckError::Mismatch(msg) = err {
-                    print_mismatches_default_message(msg);
+                match err {
+                    IdempotentCheckError::Mismatch(msg) => {
+                        print_mismatches_default_message(msg);
+                    }
+                    IdempotentCheckError::Parse => {}
                 }
                 fails += 1;
             }
@@ -724,6 +727,10 @@ fn idempotent_check(
     if parsing_errors {
         return Err(IdempotentCheckError::Parse);
     }
+    if format_report.has_warnings() {
+        // internal warnings have higher precedence than a formatting mismatch
+        return Ok(format_report);
+    }
 
     let mut write_result = HashMap::new();
     for (filename, text) in source_file {