fix: flushing rows in the end; correctly wait for drain event when wr…

…iting to transform stream. (#16)

src/XLSXRowTransform.js

@@ -1,12 +1,13 @@
 import { Transform } from 'stream';
-import { Row } from './templates';
+import { Row, SheetHeader, SheetFooter } from './templates';
 
-/** Class representing a XLSX Row transformation from array to Row. */
+/** Class representing a XLSX Row transformation from array to Row. Also adds the necessary XLSX header and footer. */
 export default class XLSXRowTransform extends Transform {
     constructor(shouldFormat) {
         super({ objectMode: true });
         this.rowCount = 0;
         this.shouldFormat = shouldFormat;
+        this.push(SheetHeader);
     }
     /**
      * Transform array to row string
@@ -18,4 +19,9 @@ export default class XLSXRowTransform extends Transform {
         this.rowCount++;
         callback(null, xlsxRow);
     }
+
+    _flush(callback) {
+        this.push(SheetFooter);
+        callback();
+    }
 }

src/XLSXTransformStream.js

@@ -1,5 +1,5 @@
 import Archiver from 'archiver';
-import { PassThrough, Transform } from 'stream';
+import { Transform } from 'stream';
 import XLSXRowTransform from './XLSXRowTransform';
 import * as templates from './templates';
 
@@ -16,10 +16,7 @@ export default class XLSXTransformStream extends Transform {
         this.initializeArchiver();
         this.rowTransform = new XLSXRowTransform(this.options.shouldFormat);
 
-        this.sheetStream = new PassThrough();
-        this.sheetStream.write(templates.SheetHeader);
-        this.rowTransform.pipe(this.sheetStream);
-        this.zip.append(this.sheetStream, {
+        this.zip.append(this.rowTransform, {
             name: 'xl/worksheets/sheet1.xml',
         });
     }
@@ -65,13 +62,15 @@ export default class XLSXTransformStream extends Transform {
     }
 
     _transform(row, encoding, callback) {
-        this.rowTransform.write(row);
-        callback();
+        if (this.rowTransform.write(row)) {
+            process.nextTick(callback);
+        } else {
+            this.rowTransform.once('drain', callback);
+        }
     }
 
-    async _flush(callback) {
-        this.sheetStream.end(templates.SheetFooter);
-        await this.zip.finalize();
-        callback();
+    _flush(callback) {
+        this.rowTransform.end();
+        this.zip.finalize().then(callback);
     }
 }

test/XLSXRowTransform.spec.js

@@ -2,14 +2,15 @@
 import { expect } from 'chai';
 import { Readable, PassThrough } from 'stream';
 import XLSXRowTransform from '../src/XLSXRowTransform';
+import { SheetHeader, SheetFooter } from '../src/templates';
 
 describe('The XLSXRowTransform', () => {
-    it('Correctly transforms an array of data into a XLSX row format', async () => {
-        const expectedResult = `
+    it('Correctly transforms an array of data into a XLSX row format with header and footer', async () => {
+        const expectedResult = `${SheetHeader}
         <row r="1" spans="1:2" x14ac:dyDescent="0.2">
             <c r="A1" t="inlineStr"><is><t>test</t></is></c>
 			<c r="B1" t="n"><v>123</v></c>
-        </row>`;
+        </row>${SheetFooter}`;
         const inputStream = Readable.from([['test', 123]]);
         const transform = new XLSXRowTransform();
         const outputStream = new PassThrough();

test/XLSXTransformStream.spec.js

@@ -5,8 +5,10 @@ import path from 'path';
 import unzipper from 'unzipper';
 import XLSXTransformStream from '../src/XLSXTransformStream';
 
+const TEST_ROWS_COUNT = 500;
+
 describe('The XLSXTransformStream', () => {
-    it('The transformed xlsx file corresponds to the snapshot xlsx file', async () => {
+    it(`The transformed xlsx file corresponds to the snapshot xlsx file (${TEST_ROWS_COUNT} rows)`, async () => {
         const snapshotFiles = {};
         await fs.createReadStream(path.resolve(__dirname, 'test.xlsx'))
             .pipe(unzipper.Parse())
@@ -18,7 +20,9 @@ describe('The XLSXTransformStream', () => {
         const inputStream = new Readable({ objectMode: true });
         const testFiles = {};
 
-        inputStream.push(['Testing', 1]);
+        for (let i = 0; i < TEST_ROWS_COUNT; i++) {
+            inputStream.push(['Testing', i + 1]);
+        }
         inputStream.push(null);
 
         await inputStream