Prevent duplicate concurrent calls of /api/*/instance in web UI (#25663)

app/javascript/mastodon/actions/server.js

@@ -19,6 +19,10 @@ export const SERVER_DOMAIN_BLOCKS_FETCH_SUCCESS = 'SERVER_DOMAIN_BLOCKS_FETCH_SU
 export const SERVER_DOMAIN_BLOCKS_FETCH_FAIL    = 'SERVER_DOMAIN_BLOCKS_FETCH_FAIL';
 
 export const fetchServer = () => (dispatch, getState) => {
+  if (getState().getIn(['server', 'server', 'isLoading'])) {
+    return;
+  }
+
   dispatch(fetchServerRequest());
 
   api(getState)
@@ -66,6 +70,10 @@ const fetchServerTranslationLanguagesFail = error => ({
 });
 
 export const fetchExtendedDescription = () => (dispatch, getState) => {
+  if (getState().getIn(['server', 'extendedDescription', 'isLoading'])) {
+    return;
+  }
+
   dispatch(fetchExtendedDescriptionRequest());
 
   api(getState)
@@ -89,6 +97,10 @@ const fetchExtendedDescriptionFail = error => ({
 });
 
 export const fetchDomainBlocks = () => (dispatch, getState) => {
+  if (getState().getIn(['server', 'domainBlocks', 'isLoading'])) {
+    return;
+  }
+
   dispatch(fetchDomainBlocksRequest());
 
   api(getState)