Forward RERUM Pagination-* headers from /query

routes/query.js

@@ -3,6 +3,8 @@ import { httpError, verifyJsonContentType } from "../rest.js"
 import { fetchRerum } from "../rerum.js"
 const router = express.Router()
 
+const PAGINATION_HEADERS = ["Pagination-Limit", "Pagination-Skip", "Pagination-Limit-Max", "Pagination-Skip-Max"]
+
 /* POST a query to the thing. */
 router.post('/', verifyJsonContentType, async (req, res, next) => {
   const lim = req.query.limit ?? 10
@@ -36,6 +38,11 @@ router.post('/', verifyJsonContentType, async (req, res, next) => {
     const queryURL = `${process.env.RERUM_API_ADDR}query?limit=${lim}&skip=${skip}`
     const rerumResponse = await fetchRerum(queryURL, queryOptions)
     .then(async (resp) => {
+      // Set before branching so the headers survive on the 502 error path as well
+      for (const header of PAGINATION_HEADERS) {
+        const value = resp.headers.get(header)
+        if (value !== null) res.set(header, value)
+      }
       if (resp.ok) return resp.json()
       // The response from RERUM indicates a failure, likely with a specific code and textual body
       let rerumErrorMessage

test/routes/query.test.js

@@ -15,6 +15,7 @@ routeTester.use(messenger)
 
 const rerumUri = `${process.env.RERUM_ID_PATTERN}_not_`
 const originalFetch = global.fetch
+const paginationHeaders = ["pagination-limit", "pagination-skip", "pagination-limit-max", "pagination-skip-max"]
 let lastFetchUrl, lastFetchOptions
 
 beforeEach(() => {
@@ -24,6 +25,7 @@ beforeEach(() => {
     lastFetchUrl = url
     lastFetchOptions = opts
     return {
+      headers: new Headers(),
       json: async () => ([{ "@id": rerumUri, test: "item", __rerum: { stuff: "here" } }]),
       ok: true,
       text: async () => "Descriptive Error Here"
@@ -118,6 +120,7 @@ describe("Check that incorrect TinyNode query route usage results in expected RE
 describe("Query upstream and network failure behavior.  __rest __core", () => {
   it("Preserves upstream text error message when query returns non-ok.", async () => {
     global.fetch = async () => ({
+      headers: new Headers(),
       ok: false,
       status: 503,
       text: async () => "Upstream query failure"
@@ -134,6 +137,7 @@ describe("Query upstream and network failure behavior.  __rest __core", () => {
 
   it("Falls back to generic RERUM error text when upstream .text() throws.", async () => {
     global.fetch = async () => ({
+      headers: new Headers(),
       ok: false,
       status: 500,
       text: async () => {
@@ -162,6 +166,60 @@ describe("Query upstream and network failure behavior.  __rest __core", () => {
 
     assert.equal(response.statusCode, 502)
     assert.match(response.text, /A RERUM error occurred/)
+    for (const header of paginationHeaders) {
+      assert.equal(response.headers[header], undefined, `${header} should not be set when RERUM was not reached`)
+    }
+  })
+})
+
+describe("Query pagination header forwarding.  __rest __core", () => {
+  it("Forwards every Pagination-* header RERUM returns on a successful query.", async () => {
+    global.fetch = async () => ({
+      headers: new Headers({
+        "Pagination-Limit": "500",
+        "Pagination-Skip": "0",
+        "Pagination-Limit-Max": "500",
+        "Pagination-Skip-Max": "100000"
+      }),
+      json: async () => ([{ "@id": rerumUri, test: "item" }]),
+      ok: true
+    })
+
+    const response = await request(routeTester)
+      .post("/query?limit=1000")
+      .set("Content-Type", "application/json")
+      .send({ test: "item" })
+
+    assert.equal(response.statusCode, 200)
+    assert.equal(response.body[0].test, "item")
+    assert.equal(response.headers["pagination-limit"], "500")
+    assert.equal(response.headers["pagination-skip"], "0")
+    assert.equal(response.headers["pagination-limit-max"], "500")
+    assert.equal(response.headers["pagination-skip-max"], "100000")
+  })
+
+  it("Forwards the Pagination-* headers RERUM returns on an error response.", async () => {
+    global.fetch = async () => ({
+      headers: new Headers({
+        "Pagination-Limit-Max": "500",
+        "Pagination-Skip-Max": "100000"
+      }),
+      ok: false,
+      status: 400,
+      text: async () => "The 'skip' URL parameter of 100001 is beyond the maximum of 100000."
+    })
+
+    const response = await request(routeTester)
+      .post("/query?skip=100001")
+      .set("Content-Type", "application/json")
+      .send({ test: "item" })
+
+    assert.equal(response.statusCode, 502)
+    assert.match(response.text, /beyond the maximum of 100000/)
+    assert.equal(response.headers["pagination-limit-max"], "500")
+    assert.equal(response.headers["pagination-skip-max"], "100000")
+    assert.equal(response.headers["pagination-limit"], undefined)
+    assert.equal(response.headers["pagination-skip"], undefined)
   })
 })