Update failed test tracking to support Mocha 6+ (microsoft#39211)

* Update failed test tracking to support Mocha 6+

* grep should not be an array

Author: rbuckton

scripts/build/tests.js

@@ -77,12 +77,23 @@ async function runConsoleTests(runJs, defaultReporter, runInParallel, watchMode,
     // timeout normally isn"t necessary but Travis-CI has been timing out on compiler baselines occasionally
     // default timeout is 2sec which really should be enough, but maybe we just need a small amount longer
     if (!runInParallel) {
-        args.push(failed ? "scripts/run-failed-tests.js" : mochaJs);
+        args.push(mochaJs);
         args.push("-R", "scripts/failed-tests");
         args.push("-O", '"reporter=' + reporter + (keepFailed ? ",keepFailed=true" : "") + '"');
         if (tests) {
             args.push("-g", `"${tests}"`);
         }
+        if (failed) {
+            const grep = fs.readFileSync(".failed-tests", "utf8")
+                .split(/\r?\n/g)
+                .map(test => test.trim())
+                .filter(test => test.length > 0)
+                .map(regExpEscape)
+                .join("|");
+            const file = path.join(os.tmpdir(), ".failed-tests.json");
+            fs.writeFileSync(file, JSON.stringify({ grep }), "utf8");
+            args.push("--config", file);
+        }
         if (colors) {
             args.push("--colors");
         }
@@ -203,3 +214,7 @@ function restoreSavedNodeEnv() {
 function deleteTemporaryProjectOutput() {
     return del(path.join(exports.localBaseline, "projectOutput/"));
 }
+
+function regExpEscape(text) {
+    return text.replace(/[.*+?^${}()|\[\]\\]/g, '\\$&');
+}