Update to improve writer interface

Add support for a single string file path instead of array
Throw useful error if relative path given to file

Author: Walker

lib/writer.js

@@ -3,18 +3,23 @@
 const { Readable } = require('stream');
 const { identifyCssModule, bundleCssModule } = require('./util');
 const { existsSync } = require('fs');
+const { isAbsolute } = require('path');
 const assert = require('assert');
 
 module.exports = class Writer extends Readable {
     constructor (files = []) {
-        assert(Array.isArray(files), `Expected 'files' to be of type 'Array', instead got '${typeof files}'`);
-        for (const file of files) {
+        super({ objectMode: true });
+
+        assert(
+            Array.isArray(files) || typeof files === 'string',
+            `Expected 'files' to be of type 'Array' or a 'string', instead got '${typeof this.files}'`
+        );
+        this.files = Array.isArray(files) ? files : [files];
+        for (const file of this.files) {
             assert(typeof file === 'string', `Expected 'file' (${file}) to be of type 'string', instead got '${typeof file}'`);
+            assert(isAbsolute(file), `Expected 'file' (${file}) to be an absolute path to a file but it was not`);
             assert(existsSync(file), `Expected 'file' (${file}) to exist on file system but it did not`);
         }
-
-        super({ objectMode: true });
-        this.files = files;
     }
 
     _read () {

test/writer.test.js

@@ -45,6 +45,34 @@ test('bundleCssModule(filePath)', async () => {
     expect(result).toMatch('dep/main.css');
 });
 
+test('new Writer(filePath)', () => {
+    const filePath = path.join(__dirname, 'test-assets/my-module-1/main.css');
+    const fileRef = 'my-module-1/main.css';
+
+    const writer = new Writer(filePath);
+    const items = [];
+
+    writer.on('data', item => {
+        items.push(item);
+    });
+
+    writer.on('end', () => {
+        const result1 = items[0];
+        const result2 = items[1];
+
+        expect(result1.id).toBe(hasher(`my-module-1|1.0.1|${fileRef}`));
+        expect(result2).toBeFalsy();
+    });
+});
+
+test('new Writer(filePath) relative paths throw error', () => {
+    const filePath = './test-assets/my-module-1/main.css';
+
+    const result = () => new Writer(filePath);
+
+    expect(result).toThrow();
+});
+
 test('new Writer([filePath])', () => {
     const filePath = path.join(__dirname, 'test-assets/my-module-1/main.css');
     const fileRef = 'my-module-1/main.css';
@@ -112,14 +140,30 @@ test('new Writer([filePath1, filePath2]) ensures correct order', () => {
     });
 });
 
-test('new Writer([filePath]) ensures filePath[] is an array', () => {
+test('new Writer([filePath]) ensures filePath[] is not null', () => {
     const filePath = null;
 
     const result = () => new Writer(filePath);
 
     expect(result).toThrow();
 });
 
+test('new Writer([filePath]) ensures filePath[] is not a number', () => {
+    const filePath = 2;
+
+    const result = () => new Writer(filePath);
+
+    expect(result).toThrow();
+});
+
+test('new Writer([filePath]) ensures filePath is not an object', () => {
+    const filePath = {};
+
+    const result = () => new Writer(filePath);
+
+    expect(result).toThrow();
+});
+
 test('new Writer([filePath]) ensures filePath[] is an array of strings', () => {
     const filePath = null;
 
@@ -128,7 +172,15 @@ test('new Writer([filePath]) ensures filePath[] is an array of strings', () => {
     expect(result).toThrow();
 });
 
-test('new Writer([filePath]) ensures valid filePaths provided', () => {
+test('new Writer([filePath]) ensures valid filePath provided', () => {
+    const filePath = 'fake.css';
+
+    const result = () => new Writer(filePath);
+
+    expect(result).toThrow();
+});
+
+test('new Writer([filePath]) ensures valid filePaths provided in array', () => {
     const filePath = 'fake.css';
 
     const result = () => new Writer([filePath]);