feat(next-drupal): translatePath, getResourceByPath - throw error whe…

…n backend error

Until now, any not-ok response from decoupled router was treated equally, as a 404 Not Found.
Behaviour is changed differentiating between 404 Not Found and server error.
The advantage is frontend holds to previous built page and doesn't update public page content
with a 404 due to backend issues.

BREAKING CHANGE:
Might break sites relying on response being the same in 404 than in 50x.

Fixes #687

packages/next-drupal/src/client.ts

@@ -673,6 +673,19 @@ export class DrupalClient {
       withAuth: options.withAuth,
     })
 
+    // Server error. But 404 is treated implicitely below.
+    if (!response?.ok && response.status !== 404) {
+      let errorMessage: string
+      try {
+        const responseJson = await response.json()
+        errorMessage = `${response.status} ${responseJson?.message}`
+      } catch (e) {
+        /* c8 ignore next 2 */
+        errorMessage = `${response.status} ${response.statusText}`
+      }
+      throw new Error(errorMessage)
+    }
+
     const json = await response.json()
 
     if (!json?.["resolvedResource#uri{0}"]?.body) {
@@ -890,10 +903,21 @@ export class DrupalClient {
     })
 
     if (!response?.ok) {
-      // Do not throw errors here.
-      // Otherwise next.js will catch error and throw a 500.
-      // We want a 404.
-      return null
+      // Do not throw errors here when response is 404.
+      if (response.status === 404) {
+        return null
+      }
+
+      // Throw error in any other situation as response is not ok.
+      let errorMessage: string
+      try {
+        const responseJson = await response.json()
+        errorMessage = `${response.status} ${responseJson?.message}`
+      } catch (e) {
+        /* c8 ignore next 2 */
+        errorMessage = `${response.status} ${response.statusText}`
+      }
+      throw new Error(errorMessage)
     }
 
     const json = await response.json()

packages/next-drupal/tests/DrupalClient/resource-methods.test.ts

@@ -449,6 +449,19 @@ describe("getResourceByPath()", () => {
     ).rejects.toThrow("Unable to resolve path /path-do-not-exist.")
   })
 
+  test("throws an error for server errors", async () => {
+    const client = new DrupalClient(BASE_URL)
+
+    spyOnFetch({
+      responseBody: { message: "mocked internal server error" },
+      status: 500,
+    })
+
+    await expect(
+      client.getResourceByPath<DrupalNode>("/server-error")
+    ).rejects.toThrow("500 mocked internal server error")
+  })
+
   test("throws an error for invalid params", async () => {
     const client = new DrupalClient(BASE_URL)
 
@@ -836,6 +849,19 @@ describe("translatePath()", () => {
     expect(path).toBeNull()
   })
 
+  test("throws an error for server errors", async () => {
+    const client = new DrupalClient(BASE_URL)
+
+    spyOnFetch({
+      responseBody: { message: "mocked internal server error" },
+      status: 500,
+    })
+
+    await expect(client.translatePath("/server-error")).rejects.toThrowError(
+      "500 mocked internal server error"
+    )
+  })
+
   test("makes un-authenticated requests by default", async () => {
     const client = new DrupalClient(BASE_URL)
     const fetchSpy = jest.spyOn(client, "fetch")