From bddfc6c4a5cad403882e8b32bbe960184d43976a Mon Sep 17 00:00:00 2001
From: Chris Van Patten <chris@vanpattenmedia.com>
Date: Mon, 8 Feb 2021 17:19:33 -0500
Subject: [PATCH 1/2] Fix: make preloaded OPTIONS requests use `parse` setting

---
 .../api-fetch/src/middlewares/preloading.js   |  6 +-
 .../src/middlewares/test/preloading.js        | 66 +++++++++++++++++++
 2 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/packages/api-fetch/src/middlewares/preloading.js b/packages/api-fetch/src/middlewares/preloading.js
index b2e787dcd6abf9..fe946ab1b0e24a 100644
--- a/packages/api-fetch/src/middlewares/preloading.js
+++ b/packages/api-fetch/src/middlewares/preloading.js
@@ -68,7 +68,11 @@ function createPreloadingMiddleware( preloadedData ) {
 				cache[ method ] &&
 				cache[ method ][ path ]
 			) {
-				return Promise.resolve( cache[ method ][ path ] );
+				return Promise.resolve(
+					parse
+						? cache[ method ][ path ].body
+						: cache[ method ][ path ]
+				);
 			}
 		}
 
diff --git a/packages/api-fetch/src/middlewares/test/preloading.js b/packages/api-fetch/src/middlewares/test/preloading.js
index 7fa3d75dfb4320..49e74e2852f495 100644
--- a/packages/api-fetch/src/middlewares/test/preloading.js
+++ b/packages/api-fetch/src/middlewares/test/preloading.js
@@ -79,6 +79,72 @@ describe( 'Preloading Middleware', () => {
 					expect( nextSpy ).toHaveBeenCalled();
 				} );
 			} );
+
+			describe( 'and the OPTIONS request has a parse flag', () => {
+				it( 'should return the full response if parse: false', () => {
+					const data = {
+						body: {
+							status: 'this is the preloaded response',
+						},
+						headers: {
+							Allow: 'GET, POST',
+						},
+					};
+
+					const preloadedData = {
+						OPTIONS: {
+							'wp/v2/posts': data,
+						},
+					};
+
+					const preloadingMiddleware = createPreloadingMiddleware(
+						preloadedData
+					);
+
+					const requestOptions = {
+						method: 'OPTIONS',
+						path: 'wp/v2/posts',
+						parse: false,
+					};
+
+					const response = preloadingMiddleware( requestOptions );
+					return response.then( ( value ) => {
+						expect( value ).toEqual( data );
+					} );
+				} );
+
+				it( 'should return only the response body if parse: true', () => {
+					const body = {
+						status: 'this is the preloaded response',
+					};
+
+					const preloadedData = {
+						OPTIONS: {
+							'wp/v2/posts': {
+								body,
+								headers: {
+									Allow: 'GET, POST',
+								},
+							},
+						},
+					};
+
+					const preloadingMiddleware = createPreloadingMiddleware(
+						preloadedData
+					);
+
+					const requestOptions = {
+						method: 'OPTIONS',
+						path: 'wp/v2/posts',
+						parse: true,
+					};
+
+					const response = preloadingMiddleware( requestOptions );
+					return response.then( ( value ) => {
+						expect( value ).toEqual( body );
+					} );
+				} );
+			} );
 		} );
 
 		describe( 'when the requested data is not from a preloaded endpoint', () => {

From 6f848d85ee10154332ee57bf28c50000646162b7 Mon Sep 17 00:00:00 2001
From: Chris Van Patten <chris@vanpattenmedia.com>
Date: Wed, 14 Apr 2021 11:54:45 -0400
Subject: [PATCH 2/2] add: Changelog entry and fix typo in test

---
 packages/api-fetch/CHANGELOG.md                       | 4 ++++
 packages/api-fetch/src/middlewares/test/preloading.js | 4 ++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/packages/api-fetch/CHANGELOG.md b/packages/api-fetch/CHANGELOG.md
index 0e59192086e1de..532e820aa5c637 100644
--- a/packages/api-fetch/CHANGELOG.md
+++ b/packages/api-fetch/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Breaking changes
+
+- `OPTIONS` requests which are handled by the preloading middleware are no longer resolved as unparsed responses unless you explicitly set `parse: false`, for consistency with other request methods. If you expect an unparsed response, add `{ parse: false }` to your request options to preserve the previous behavior.
+
 ## 3.8.1 (2019-04-22)
 
 - Added deprecation to `useApiFetch` hook.
diff --git a/packages/api-fetch/src/middlewares/test/preloading.js b/packages/api-fetch/src/middlewares/test/preloading.js
index 49e74e2852f495..3f470e9a8a6e69 100644
--- a/packages/api-fetch/src/middlewares/test/preloading.js
+++ b/packages/api-fetch/src/middlewares/test/preloading.js
@@ -205,7 +205,7 @@ describe( 'Preloading Middleware', () => {
 			[ 'method empty', { [ method ]: {} } ],
 		] )( '%s', ( label, preloadedData ) => {
 			it( 'should move to the next middleware if no preloaded data', () => {
-				const prelooadingMiddleware = createPreloadingMiddleware(
+				const preloadingMiddleware = createPreloadingMiddleware(
 					preloadedData
 				);
 				const requestOptions = {
@@ -218,7 +218,7 @@ describe( 'Preloading Middleware', () => {
 					return true;
 				};
 
-				const ret = prelooadingMiddleware( requestOptions, callback );
+				const ret = preloadingMiddleware( requestOptions, callback );
 				expect( ret ).toBe( true );
 			} );
 		} );