Don't dump diagnostics json if not absolutely necessary

Author: oli-obk

src/json.rs

@@ -62,19 +62,20 @@ struct DiagnosticCode {
     explanation: Option<String>,
 }
 
-pub fn extract_rendered(output: &str, proc_res: &ProcRes) -> String {
+pub fn extract_rendered(output: &str) -> String {
     output
         .lines()
         .filter_map(|line| {
             if line.starts_with('{') {
                 match serde_json::from_str::<Diagnostic>(line) {
                     Ok(diagnostic) => diagnostic.rendered,
                     Err(error) => {
-                        proc_res.fatal(Some(&format!(
+                        print!(
                             "failed to decode compiler output as json: \
                              `{}`\nline: {}\noutput: {}",
                             error, line, output
-                        )));
+                        );
+                        panic!()
                     }
                 }
             } else {

src/runtest.rs

@@ -2760,7 +2760,7 @@ impl<'test> TestCx<'test> {
         let stderr = if explicit {
             proc_res.stderr.clone()
         } else {
-            json::extract_rendered(&proc_res.stderr, &proc_res)
+            json::extract_rendered(&proc_res.stderr)
         };
 
         let normalized_stderr = self.normalize_output(&stderr, &self.props.normalize_stderr);
@@ -3377,7 +3377,9 @@ impl ProcRes {
              {}\n\
              ------------------------------------------\n\
              \n",
-            self.status, self.cmdline, self.stdout, self.stderr
+            self.status, self.cmdline,
+            json::extract_rendered(&self.stdout),
+            json::extract_rendered(&self.stderr),
         );
         panic!();
     }