chore: add proxy backend (#3126)

* feat(backends): add proxy backend

* feat: add proxy server initial commit

* fix: move from joi to @hapi/joi

* test: add joi validation tests

* feat: proxy server initial implementations

* test: add tests, fix build

* chore: update yarn.lock

* build: fix develop command

* fix(back-proxy): fix bugs

* test(backend-proxy): add cypress tests

* chore: cleanup

* chore: support node 10

* chore: code cleanup

* chore: run cypress on ubuntu 16.04

* test(e2e): fix proxy backend cypress tests

* chore: don't start proxy server on yarn develop

packages/netlify-cms-core/src/actions/mediaLibrary.ts

@@ -489,18 +489,20 @@ export async function getMediaDisplayURL(
     // url loading had an error
     url = null;
   } else {
-    if (!displayURLState.get('isFetching')) {
-      // load display url
-      dispatch(loadMediaDisplayURL(file));
-    }
-
     const key = file.id;
-    url = await waitUntilWithTimeout<string>(dispatch, resolve => ({
+    const promise = waitUntilWithTimeout<string>(dispatch, resolve => ({
       predicate: ({ type, payload }) =>
         (type === MEDIA_DISPLAY_URL_SUCCESS || type === MEDIA_DISPLAY_URL_FAILURE) &&
         payload.key === key,
       run: (_dispatch, _getState, action) => resolve(action.payload.url),
     }));
+
+    if (!displayURLState.get('isFetching')) {
+      // load display url
+      dispatch(loadMediaDisplayURL(file));
+    }
+
+    url = await promise;
   }
 
   return url;

packages/netlify-cms-core/src/actions/waitUntil.ts

@@ -22,17 +22,26 @@ export const waitUntilWithTimeout = async <T>(
     dispatch(waitUntil(waitActionArgs(resolve)));
   });
 
-  const timeoutPromise = new Promise<T>((resolve, reject) => {
-    setTimeout(() => (waitDone ? resolve() : reject(new Error('Wait Action timed out'))), timeout);
+  const timeoutPromise = new Promise<T | null>(resolve => {
+    setTimeout(() => {
+      if (waitDone) {
+        resolve();
+      } else {
+        console.warn('Wait Action timed out');
+        resolve(null);
+      }
+    }, timeout);
   });
 
   const result = await Promise.race([
-    waitPromise.then(result => {
-      waitDone = true;
-      return result;
-    }),
+    waitPromise
+      .then(result => {
+        waitDone = true;
+        return result;
+      })
+      .catch(null),
     timeoutPromise,
-  ]).catch(null);
+  ]);
 
   return result;
 };