reads trace file line by line

readFileSync does not read large files
nodejs/node#9489

Author: Marcin Rudolf

lib/app.js

@@ -185,15 +185,6 @@ class App {
       this.testsErrored = shell.error();
       shell.cd('./..');
     } catch (err) {
-      this.cleanUp(err);
-    }
-
-    // Get events fired during instrumented contracts execution.
-    try {
-      this.events = fs.readFileSync('./allFiredEvents').toString().split('\n');
-      this.events.pop();
-    } catch (err) {
-      const msg =
       `
         There was an error generating coverage. Possible reasons include:
         1. Another application is using port ${this.port}
@@ -212,25 +203,39 @@ class App {
     const reporter = new istanbul.Reporter();
 
     return new Promise((resolve, reject) => {
-      try {
-        this.coverage.generate(this.events, `${this.workingDir}/contracts`);
-
-        const json = JSON.stringify(this.coverage.coverage);
-        fs.writeFileSync('./coverage.json', json);
-
-        collector.add(this.coverage.coverage);
-        reporter.add('html');
-        reporter.add('lcov');
-        reporter.add('text');
-        reporter.write(collector, true, () => {
-          this.log('Istanbul coverage reports generated');
-          this.cleanUp();
-          resolve();
+      // Get events fired during instrumented contracts execution.
+      const stream = fs.createReadStream(`${this.workingDir}/allFiredEvents`);
+      stream.on('error', (err) => this.cleanUp('Event trace file not found.\n' + err));
+      const reader = require('readline').createInterface({
+        input: stream
+      });
+      this.events = [];
+      reader
+        .on('line', (line) => this.events.push(line))
+        .on('close', () => {
+          // Generate Istanbul report
+          try {
+            // console.log(`got ${this.events.length} events`);
+            this.coverage.generate(this.events, `${this.workingDir}/contracts`);
+
+            const json = JSON.stringify(this.coverage.coverage);
+            fs.writeFileSync('./coverage.json', json);
+
+            collector.add(this.coverage.coverage);
+            reporter.add('html');
+            reporter.add('lcov');
+            reporter.add('text');
+            reporter.write(collector, true, () => {
+              this.log('Istanbul coverage reports generated');
+              this.cleanUp();
+              resolve();
+            });
+          } catch (err) {
+            const msg = 'There was a problem generating the coverage map / running Istanbul.\n';
+            console.log(err.stack);
+            this.cleanUp(msg + err);
+          }
         });
-      } catch (err) {
-        const msg = 'There was a problem generating the coverage map / running Istanbul.\n';
-        this.cleanUp(msg + err);
-      }
     });
   }