benchmark: improve cli error message

When no matching benchmark files are found, a more sensible error
is shown now.

PR-URL: https://github.com/nodejs/node/pull/12421
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Alexey Orlenko <eaglexrlnk@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

benchmark/_cli.js

@@ -88,6 +88,8 @@ CLI.prototype.benchmarks = function() {
   const filter = this.optional.filter || false;
 
   for (const category of this.items) {
+    if (benchmarks[category] === undefined)
+      continue;
     for (const scripts of benchmarks[category]) {
       if (filter && scripts.lastIndexOf(filter) === -1) continue;
 

benchmark/compare.js

@@ -35,7 +35,7 @@ const runs = cli.optional.runs ? parseInt(cli.optional.runs, 10) : 30;
 const benchmarks = cli.benchmarks();
 
 if (benchmarks.length === 0) {
-  console.error('no benchmarks found');
+  console.error('No benchmarks found');
   process.exitCode = 1;
   return;
 }