fix: only invoke WDS tap when there are issues (#547)

`webpack-dev-server` always performs a hot reload when its `sync` tap runs. As a result, `fork-ts-checker-webpack-plugin` triggers a hot reload upon completion in `async` mode even when no issues are reported. This commit adds a check for issues before invoking `webpack-dev-server`'s `sync` tap, which eliminates the unneeded reload.

Author: tessro

src/hooks/tapDoneToAsyncGetIssues.ts

@@ -67,7 +67,9 @@ function tapDoneToAsyncGetIssues(
       configuration.logger.issues.log(chalk.green('No issues found.'));
     }
 
-    if (state.webpackDevServerDoneTap) {
+    // report issues to webpack-dev-server, if it's listening
+    // skip reporting if there are no issues, to avoid an extra hot reload
+    if (issues.length && state.webpackDevServerDoneTap) {
       issues.forEach((issue) => {
         const error = new IssueWebpackError(configuration.formatter(issue), issue);