Ensure we finish writing the report to stdout

Author: Ju Liu

lib/report.js

@@ -2,7 +2,7 @@ const styledMessage = require('./styled-message');
 
 module.exports = report;
 
-function report(options, result) {
+async function report(options, result) {
   if (options.report === 'json') {
     return print(options, jsonReport(result.errors));
   }
@@ -22,22 +22,46 @@ function jsonReport(errors) {
 function print(options, json) {
   if (options.reportOnOneLine) {
     if (json.type === 'review-errors') {
-      json.errors.forEach((errorForFile) => {
-        errorForFile.errors.forEach((error) => {
-          console.log(
-            JSON.stringify({
-              path: errorForFile.path,
-              ...error
+      if (json.errors.length > 0) {
+        return safeConsoleLog(
+          json.errors
+            .map((errorForFile) => {
+              return errorForFile.errors
+                .map((error) => {
+                  return JSON.stringify({
+                    path: errorForFile.path,
+                    ...error
+                  });
+                })
+                .join('\n');
             })
-          );
-        });
-      });
+            .join('\n')
+        );
+      }
     } else {
-      console.log(JSON.stringify(json));
+      return safeConsoleLog(JSON.stringify(json));
     }
   } else {
-    console.log(
+    return safeConsoleLog(
       JSON.stringify(json, null, options.debug || options.forTests ? 2 : 0)
     );
   }
 }
+
+// Printing large outputs to stdout is not recommended because at times
+// console.log is asynchronous and returns before ensuring that the whole
+// output has been printed. Check out these links for more details:
+//
+// - https://nodejs.org/api/process.html#process_process_exit_code
+// - https://github.com/nodejs/node/issues/6456
+// - https://github.com/nodejs/node/issues/19218
+//
+// Using process.stdout.write and passing a function ensures that
+// the whole output has been written.
+function safeConsoleLog(message) {
+  return new Promise((resolve) => {
+    process.stdout.write(message + '\n', () => {
+      resolve();
+    });
+  });
+}

lib/run-review.js

@@ -23,7 +23,7 @@ async function runReview(options, app) {
   });
   Benchmark.end(options, 'review');
 
-  report(options, result);
+  await report(options, result);
 
   return result.success;
 }

lib/runner.js

@@ -76,11 +76,12 @@ async function initializeApp(options, elmModulePath, reviewElmJson) {
   autofix.subscribe(options, app);
   if (options.watch) {
     AppState.subscribe(app.ports.reviewReport, (result) => {
-      report(options, result);
-      const shouldReReview = AppState.reviewFinished();
-      if (shouldReReview) {
-        return startReview(options, app);
-      }
+      return report(options, result).then(() => {
+        const shouldReReview = AppState.reviewFinished();
+        if (shouldReReview) {
+          return startReview(options, app);
+        }
+      });
     });
   }