fix: resolve relative paths when creating URLs (#204)

packages/v8env/src/url.ts

@@ -131,7 +131,7 @@ export class URL {
         password: baseParts.password,
         hostname: baseParts.hostname,
         port: baseParts.port,
-        path: urlParts.path || baseParts.path,
+        path: resolvePathFromBase(urlParts.path, baseParts.path),
         query: urlParts.query || baseParts.query,
         hash: urlParts.hash
       }
@@ -280,4 +280,14 @@ export class URL {
   }
 }
 
+function resolvePathFromBase(path: string, basePath: string) {
+  if (path.startsWith("/")) {
+    return path
+  }
+  if (basePath.endsWith("/")) {
+    return basePath + path
+  }
+  return basePath + "/" + path
+}
+
 URL.init()

tests/v8env/tests/url.spec.js

@@ -0,0 +1,24 @@
+import { expect } from "chai"
+
+describe("URL", () => {
+  it("ensures pathname begins with a slash", () => {
+    const url = new URL("https://fly.io/about")
+    url.pathname = "team"
+    expect(url.pathname).to.equal("/team")
+  })
+
+  it("resolves a relative path from a base", () => {
+    const url = new URL("fly", new URL("https://github.com/superfly/"))
+    expect(url.pathname).to.equal("/superfly/fly")
+  })
+
+  it("resolves an absolte path from a base", () => {
+    const url = new URL("/about", new URL("https://fly.io/path/"))
+    expect(url.pathname).to.equal("/about")
+  })
+
+  it("inserts trailing slash if needed", () => {
+    const url = new URL("fly", new URL("https://github.com/superfly"))
+    expect(url.pathname).to.equal("/superfly/fly")
+  })
+})