feat: adds X-HTTP-Method-Override header (#6487)

Fixes: https://github.com/payloadcms/payload/issues/6486

Adds `X-HTTP-Method-Override` header to allow for sending query params in the body of a POST request. This is useful when the query param string hits the upper limit.

docs/rest-api/overview.mdx

@@ -618,3 +618,45 @@ export const Orders: CollectionConfig = {
   **req** will have the **payload** object and can be used inside your endpoint handlers for making
   calls like req.payload.find() that will make use of access control and hooks.
 </Banner>
+
+## Method Override for GET Requests
+
+Payload supports a method override feature that allows you to send GET requests using the HTTP POST method. This can be particularly useful in scenarios when the query string in a regular GET request is too long.
+
+### How to Use
+
+To use this feature, include the `X-HTTP-Method-Override` header set to `GET` in your POST request. The parameters should be sent in the body of the request with the `Content-Type` set to `application/x-www-form-urlencoded`.
+
+### Example
+
+Here is an example of how to use the method override to perform a GET request:
+
+#### Using Method Override (POST)
+
+```ts
+const res = await fetch(`${api}/${collectionSlug}`, {
+  method: 'POST',
+  credentials: 'include',
+  headers: {
+    'Accept-Language': i18n.language,
+    'Content-Type': 'application/x-www-form-urlencoded',
+    'X-HTTP-Method-Override': 'GET',
+  },
+  body: qs.stringify({
+    depth: 1,
+    locale: 'en',
+  }),
+})
+```
+
+#### Equivalent Regular GET Request
+
+```ts
+const res = await fetch(`${api}/${collectionSlug}?depth=1&locale=en`, {
+  method: 'GET',
+  credentials: 'include',
+  headers: {
+    'Accept-Language': i18n.language,
+  },
+})
+```

packages/next/src/routes/rest/index.ts

@@ -407,6 +407,11 @@ export const POST =
     let res: Response
     let collection: Collection
 
+    const overrideHttpMethod = request.headers.get('X-HTTP-Method-Override')
+    if (overrideHttpMethod === 'GET') {
+      return await GET(config)(request, { params: { slug } })
+    }
+
     try {
       req = await createPayloadRequest({
         config,

packages/next/src/utilities/createPayloadRequest.ts

@@ -58,6 +58,17 @@ export const createPayloadRequest = async ({
     fallbackLocale = locales.fallbackLocale
   }
 
+  const overrideHttpMethod = request.headers.get('X-HTTP-Method-Override')
+  const queryToParse = overrideHttpMethod === 'GET' ? await request.text() : urlProperties.search
+
+  const query = queryToParse
+    ? qs.parse(queryToParse, {
+        arrayLimit: 1000,
+        depth: 10,
+        ignoreQueryPrefix: true,
+      })
+    : {}
+
   const customRequest: CustomPayloadRequestProperties = {
     context: {},
     fallbackLocale,
@@ -74,13 +85,7 @@ export const createPayloadRequest = async ({
     payloadUploadSizes: {},
     port: urlProperties.port,
     protocol: urlProperties.protocol,
-    query: urlProperties.search
-      ? qs.parse(urlProperties.search, {
-          arrayLimit: 1000,
-          depth: 10,
-          ignoreQueryPrefix: true,
-        })
-      : {},
+    query,
     routeParams: params || {},
     search: urlProperties.search,
     searchParams: urlProperties.searchParams,

packages/ui/src/fields/Relationship/index.tsx

@@ -201,11 +201,15 @@ const RelationshipField: React.FC<RelationshipFieldProps> = (props) => {
               query.where.and.push(relationFilterOption)
             }
 
-            const response = await fetch(`${serverURL}${api}/${relation}?${qs.stringify(query)}`, {
+            const response = await fetch(`${serverURL}${api}/${relation}`, {
+              body: qs.stringify(query),
               credentials: 'include',
               headers: {
                 'Accept-Language': i18n.language,
+                'Content-Type': 'application/x-www-form-urlencoded',
+                'X-HTTP-Method-Override': 'GET',
               },
+              method: 'POST',
             })
 
             if (response.ok) {
@@ -326,11 +330,15 @@ const RelationshipField: React.FC<RelationshipFieldProps> = (props) => {
         }
 
         if (!errorLoading) {
-          const response = await fetch(`${serverURL}${api}/${relation}?${qs.stringify(query)}`, {
+          const response = await fetch(`${serverURL}${api}/${relation}`, {
+            body: qs.stringify(query),
             credentials: 'include',
             headers: {
               'Accept-Language': i18n.language,
+              'Content-Type': 'application/x-www-form-urlencoded',
+              'X-HTTP-Method-Override': 'GET',
             },
+            method: 'POST',
           })
 
           const collection = collections.find((coll) => coll.slug === relation)

test/fields-relationship/e2e.spec.ts

@@ -569,6 +569,58 @@ describe('fields - relationship', () => {
       ).toHaveCount(15)
     })
   })
+
+  describe('field relationship with many items', () => {
+    beforeEach(async () => {
+      const relations: string[] = []
+      const batchSize = 10
+      const totalRelations = 300
+      const totalBatches = Math.ceil(totalRelations / batchSize)
+      for (let i = 0; i < totalBatches; i++) {
+        const batchPromises: Promise<RelationOne>[] = []
+        const start = i * batchSize
+        const end = Math.min(start + batchSize, totalRelations)
+
+        for (let j = start; j < end; j++) {
+          batchPromises.push(
+            payload.create({
+              collection: relationOneSlug,
+              data: {
+                name: 'relation',
+              },
+            }),
+          )
+        }
+
+        const batchRelations = await Promise.all(batchPromises)
+        relations.push(...batchRelations.map((doc) => doc.id))
+      }
+
+      await payload.update({
+        id: docWithExistingRelations.id,
+        collection: slug,
+        data: {
+          relationshipHasMany: relations,
+        },
+      })
+    })
+
+    test('should update with new relationship', async () => {
+      await page.goto(url.edit(docWithExistingRelations.id))
+
+      const field = page.locator('#field-relationshipHasMany')
+      const dropdownIndicator = field.locator('.dropdown-indicator')
+      await dropdownIndicator.click({ delay: 100 })
+
+      const options = page.locator('.rs__option')
+      await expect(options).toHaveCount(2)
+
+      await options.nth(0).click()
+      await expect(field).toContainText(relationOneDoc.id)
+
+      await saveDocAndAssert(page)
+    })
+  })
 })
 
 async function clearAllDocs(): Promise<void> {