refactor: outputData as a proper PWMetrics method

bin/cli.js

@@ -4,9 +4,6 @@
 'use strict';
 
 /* eslint-disable no-logger */
-const sysPath = require('path');
-const fs = require('fs');
-const os = require('os');
 const yargs = require('yargs');
 
 const PWMetrics = require('../lib/index');
@@ -95,34 +92,13 @@ options.url = cliFlags._[0] || options.url;
 if (!options.url || !options.url.length)
   throw new Error(getMessage('NO_URL'));
 
-const writeToDisk = function(fileName, data) {
-  return new Promise((resolve, reject) => {
-    const path = sysPath.join(process.cwd(), fileName);
-    fs.writeFile(path, data, err => {
-      if (err) reject(err);
-      logger.log(getMessageWithPrefix('SUCCESS', 'SAVED_TO_JSON', path));
-      resolve();
-    });
-  });
-};
 
 const pwMetrics = new PWMetrics(options.url, options);
-pwMetrics.start(data => {
-  if (options.flags.json) {
-    // serialize accordingly
-    const formattedData = JSON.stringify(data, null, 2) + os.EOL;
-    // output to file.
-    if (options.flags.outputPath !== 'stdout') {
-      writeToDisk(options.flags.outputPath, formattedData);
-    // output to stdout
-    } else if (formattedData) {
-      process.stdout.write(formattedData);
-    }
-  }
-})
+pwMetrics.start()
   .then(() => {
     process.exit(0);
-  }).catch(err => {
+  })
+  .catch(err => {
     logger.error(err);
     process.exit(1);
   });

lib/index.ts

@@ -4,19 +4,23 @@
 declare var process: {
   stdout: {
     columns: string;
+    write: Function;
   }
 };
 
 const opn = require('opn');
+const os = require('os');
 const path = require('path');
 
+
 import {METRICS} from './metrics/metrics';
 import {Logger} from './utils/logger';
 import {LHRunner} from './lh-runner';
 import {Sheets} from './sheets';
 import {adaptMetricsData} from './metrics/metrics-adapter';
 import {validateMetrics, normalizeExpectationMetrics, checkExpectations} from './expectations';
 import {upload} from './upload';
+import {writeToDisk} from './utils/fs';
 import {getMessage, getMessageWithPrefix} from './utils/messages';
 import {drawChart} from './chart/chart';
 
@@ -45,6 +49,7 @@ class PWMetrics {
     chromeFlags: '',
     showOutput: true,
     failOnError: false,
+    outputPath: 'stdout',
   };
   runs: number;
   sheets: SheetsConfig;
@@ -74,7 +79,7 @@ class PWMetrics {
     this.logger = Logger.getInstance({showOutput: this.flags.showOutput});
   }
 
-  async start(outputDataCallback) {
+  async start() {
     const runs = Array.apply(null, {length: +this.runs}).map(Number.call, Number);
     let metricsResults: MetricsResults[] = [];
 
@@ -100,9 +105,7 @@ class PWMetrics {
       await sheets.appendResults(results.runs);
     }
 
-    if (outputDataCallback) {
-      outputDataCallback(results);
-    }
+    await this.outputData(results);
 
     if (this.flags.expectations) {
       const resultsToCompare = this.runs > 1 ? results.median.timings : results[0].timings;
@@ -216,6 +219,20 @@ class PWMetrics {
       opn(getTimelineViewerUrl(id));
     }
   }
+
+  outputData(data: PWMetricsResults) {
+    if (this.flags.json) {
+      // serialize accordingly
+      const formattedData = JSON.stringify(data, null, 2) + os.EOL;
+      // output to file.
+      if (this.flags.outputPath !== 'stdout') {
+        return writeToDisk(this.flags.outputPath, formattedData);
+      // output to stdout
+      } else if (formattedData) {
+        return Promise.resolve(process.stdout.write(formattedData));
+      }
+    }
+  }
 }
 
 module.exports = PWMetrics;

lib/utils/fs.ts

@@ -2,8 +2,16 @@
 // Licensed under the Apache License, Version 2.0. See LICENSE
 
 import * as path from 'path';
+import * as fs from 'fs';
+import * as promisify from 'micro-promisify';
 
-function getConfigFromFile(fileName: string = 'package.json') {
+import {getMessageWithPrefix} from './messages';
+import {Logger} from './logger';
+
+const logger = Logger.getInstance();
+
+
+export function getConfigFromFile(fileName: string = 'package.json') {
   let resolved: string;
   try {
     resolved = require.resolve(`./${fileName}`);
@@ -17,7 +25,20 @@ function getConfigFromFile(fileName: string = 'package.json') {
       return config.pwmetrics || {};
     else return config;
   } else throw new Error(`Invalid config from ${fileName}`);
-  
+
 }
 
-module.exports = { getConfigFromFile };
+export function writeToDisk(fileName: string, data: string) {
+  return new Promise(async (resolve, reject) => {
+    const filePath = path.join(process.cwd(), fileName);
+
+    try {
+      await promisify(fs.writeFile)(filePath, data);
+    } catch (err) {
+      reject(err);
+    }
+
+    logger.log(getMessageWithPrefix('SUCCESS', 'SAVED_TO_JSON', filePath));
+    resolve();
+  });
+}

types/types.ts

@@ -29,6 +29,7 @@ export interface FeatureFlags {
   port?: number;
   showOutput: Boolean;
   failOnError: Boolean;
+  outputPath: string;
 }
 
 export interface MetricsResults {