(feat) add argument --null-as-default-value to use null as default value for extracted translations

tests/post-processors/null-as-default-value.post-processor.spec.ts

@@ -0,0 +1,42 @@
+import { expect } from 'chai';
+
+import { PostProcessorInterface } from '../../src/post-processors/post-processor.interface';
+import { NullAsDefaultValuePostProcessor } from '../../src/post-processors/null-as-default-value.post-processor';
+import { TranslationCollection } from '../../src/utils/translation.collection';
+
+describe('NullAsDefaultValuePostProcessor', () => {
+
+	let processor: PostProcessorInterface;
+
+	beforeEach(() => {
+		processor = new NullAsDefaultValuePostProcessor();
+	});
+
+	it('should use null as default value', () => {
+		const draft = new TranslationCollection({ 'String A': '' });
+		const extracted = new TranslationCollection({ 'String A': '' });
+		const existing = new TranslationCollection();
+		expect(processor.process(draft, extracted, existing).values).to.deep.equal({
+			'String A': null
+		});
+	});
+
+	it('should keep existing value even if it is an empty string', () => {
+		const draft = new TranslationCollection({ 'String A': '' });
+		const extracted = new TranslationCollection({ 'String A': '' });
+		const existing = new TranslationCollection({ 'String A': '' });
+		expect(processor.process(draft, extracted, existing).values).to.deep.equal({
+			'String A': ''
+		});
+	});
+
+	it('should keep existing value', () => {
+		const draft = new TranslationCollection({ 'String A': 'Streng A' });
+		const extracted = new TranslationCollection({ 'String A': 'Streng A' });
+		const existing = new TranslationCollection({ 'String A': 'Streng A' });
+		expect(processor.process(draft, extracted, existing).values).to.deep.equal({
+			'String A': 'Streng A'
+		});
+	});
+
+});