chore: import upstream snapshot with attribution

packages/shared/src/utils/polyvinyl.test.ts

@@ -0,0 +1,30 @@
+import { describe, it, expect } from 'vitest';
+import { createPoly, createSource } from './polyvinyl';
+
+const polyData = {
+  name: 'test',
+  ext: 'js',
+  contents: 'var hello = world;',
+  history: ['test.js']
+};
+
+describe('createSource', () => {
+  it('should return a vinyl object with a source matching the contents', () => {
+    const original = createPoly(polyData);
+
+    const updated = createSource(original);
+    expect(original).not.toHaveProperty('source');
+    expect(updated).toHaveProperty('source', 'var hello = world;');
+    expect(updated).toMatchObject(original);
+  });
+
+  it('should not update the source if it already exists', () => {
+    const original = createPoly({
+      ...polyData,
+      source: 'const hello = world;'
+    });
+
+    const updated = createSource(original);
+    expect(updated).toStrictEqual(original);
+  });
+});