Add issue subscription check to API (#10967)

close #10962

Adds `GET /api/v1​/repos​/{owner}​/{repo}​/issues​/{index}​/subscriptions​/check`
 -> return a `WachInfo`

models/issue.go

@@ -332,6 +332,13 @@ func (issue *Issue) GetIsRead(userID int64) error {
 
 // APIURL returns the absolute APIURL to this issue.
 func (issue *Issue) APIURL() string {
+	if issue.Repo == nil {
+		err := issue.LoadRepo()
+		if err != nil {
+			log.Error("Issue[%d].APIURL(): %v", issue.ID, err)
+			return ""
+		}
+	}
 	return fmt.Sprintf("%s/issues/%d", issue.Repo.APIURL(), issue.Index)
 }
 

models/issue_watch.go

@@ -64,6 +64,23 @@ func getIssueWatch(e Engine, userID, issueID int64) (iw *IssueWatch, exists bool
 	return
 }
 
+// CheckIssueWatch check if an user is watching an issue
+// it takes participants and repo watch into account
+func CheckIssueWatch(user *User, issue *Issue) (bool, error) {
+	iw, exist, err := getIssueWatch(x, user.ID, issue.ID)
+	if err != nil {
+		return false, err
+	}
+	if exist {
+		return iw.IsWatching, nil
+	}
+	w, err := getWatch(x, user.ID, issue.RepoID)
+	if err != nil {
+		return false, err
+	}
+	return isWatchMode(w.Mode) || IsUserParticipantsOfIssue(user, issue), nil
+}
+
 // GetIssueWatchersIDs returns IDs of subscribers or explicit unsubscribers to a given issue id
 // but avoids joining with `user` for performance reasons
 // User permissions must be verified elsewhere if required