Add support for relative URLs

src/http/httpError.test.ts

@@ -18,7 +18,7 @@
 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 // SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 //
-import { describe, it, expect } from "@jest/globals";
+import { describe, it, expect, jest } from "@jest/globals";
 import { ClientHttpError } from "./httpError";
 import { mockProblemDetails } from "./problemDetails.mock";
 import {
@@ -189,4 +189,34 @@ describe("ClientHttpError", () => {
       new ClientHttpError(response, "Not important", "Some error message");
     }).toThrow(InruptClientError);
   });
+
+  it("supports relative URLs for type and instance", () => {
+    const responseUrl = "https://example.org/resource";
+    const relativeTypeUrl = "../type";
+    const relativeInstanceUrl = "../instance";
+    const response = new Response(undefined, {
+      status: 400,
+      statusText: "Bad Request",
+      headers: new Headers({
+        "Content-Type": "application/problem+json",
+      }),
+    });
+    jest.spyOn(response, "url", "get").mockReturnValue(responseUrl);
+    const { problemDetails: mockedProblemDetails } = mockProblemDetails({});
+    const error = new ClientHttpError(
+      response,
+      JSON.stringify({
+        ...mockedProblemDetails,
+        type: relativeTypeUrl,
+        instance: relativeInstanceUrl,
+      }),
+      "Some error message",
+    );
+    expect(error.problemDetails.type.href).toStrictEqual(
+      new URL(relativeTypeUrl, responseUrl).href,
+    );
+    expect(error.problemDetails.instance?.href).toStrictEqual(
+      new URL(relativeInstanceUrl, responseUrl).href,
+    );
+  });
 });

src/http/problemDetails.ts

@@ -125,9 +125,9 @@ export function hasProblemDetails(
   return isProblemDetails((error as WithProblemDetails).problemDetails);
 }
 
-function asUrl(url: string): URL | undefined {
+function asUrl(url: string, base: string): URL | undefined {
   try {
-    return new URL(url);
+    return new URL(url, base);
   } catch {
     return undefined;
   }
@@ -153,7 +153,7 @@ export function buildProblemDetails(response: ErrorResponse): ProblemDetails {
   if (response.headers.get("Content-Type") === PROBLEM_DETAILS_MIME) {
     try {
       const responseBody = JSON.parse(response.body);
-      const responseType = asUrl(responseBody.type);
+      const responseType = asUrl(responseBody.type, response.url);
       if (responseType !== undefined) {
         type = responseType;
       }
@@ -166,7 +166,7 @@ export function buildProblemDetails(response: ErrorResponse): ProblemDetails {
       if (typeof responseBody.detail === "string") {
         detail = responseBody.detail;
       }
-      const responseInstance = asUrl(responseBody.instance);
+      const responseInstance = asUrl(responseBody.instance, response.url);
       if (responseInstance !== undefined) {
         instance = responseInstance;
       }