fix: normalize-asset-prefix adding leading slash when URL assetPrefix is provided

packages/next/src/shared/lib/normalized-asset-prefix.test.ts

@@ -0,0 +1,39 @@
+import { normalizedAssetPrefix } from './normalized-asset-prefix'
+
+describe('normalizedAssetPrefix', () => {
+  it('should return an empty string when assetPrefix is nullish', () => {
+    expect(normalizedAssetPrefix(undefined)).toBe('')
+  })
+
+  it('should return an empty string when assetPrefix is an empty string', () => {
+    expect(normalizedAssetPrefix('')).toBe('')
+  })
+
+  it('should return an empty string when assetPrefix is a single slash', () => {
+    expect(normalizedAssetPrefix('/')).toBe('')
+  })
+
+  // we expect an empty string because it could be an unnecessary trailing slash
+  it('should remove leading slash(es) when assetPrefix has more than one', () => {
+    expect(normalizedAssetPrefix('///path/to/asset')).toBe('/path/to/asset')
+  })
+
+  it('should not remove the leading slash when assetPrefix has only one', () => {
+    expect(normalizedAssetPrefix('/path/to/asset')).toBe('/path/to/asset')
+  })
+
+  it('should add a leading slash when assetPrefix is missing one', () => {
+    expect(normalizedAssetPrefix('path/to/asset')).toBe('/path/to/asset')
+  })
+
+  it('should return a URL without protocol when assetPrefix is a URL', () => {
+    // TODO: this is for comparison, remove this before PR merge
+    expect(normalizedAssetPrefix('https://example.com/path/to/asset')).not.toBe(
+      '/https://example.com/path/to/asset'
+    )
+
+    expect(normalizedAssetPrefix('https://example.com/path/to/asset')).toBe(
+      'example.com/path/to/asset'
+    )
+  })
+})