enhance: auto redirects to source page when alias page is empty

More info here: https://discuss.logseq.com/t/improve-implementation-of-aliases/81/22?u=tienson

src/main/frontend/components/block.cljs

@@ -251,24 +251,26 @@
                                (string/capitalize original-page-name)
                                original-page-name)
           page (string/lower-case page-name)
-          source-page-name (or (when source-page (:page/name source-page))
+          redirect-page-name (if (db/page-empty? (state/get-current-repo) page-name)
+                               (or (when source-page (:page/name source-page))
+                                   page)
                                page)
           href (if html-export?
                  (util/encode-str page)
-                 (rfe/href :page {:name source-page-name}))]
+                 (rfe/href :page {:name redirect-page-name}))]
       [:a.page-ref
        {:href href
         :on-click (fn [e]
                     (util/stop e)
                     (if (gobj/get e "shiftKey")
-                      (when-let [page-entity (db/entity [:page/name source-page-name])]
+                      (when-let [page-entity (db/entity [:page/name redirect-page-name])]
                         (state/sidebar-add-block!
                          (state/get-current-repo)
                          (:db/id page-entity)
                          :page
                          {:page page-entity}))
                       (route-handler/redirect! {:to :page
-                                                :path-params {:name source-page-name}}))
+                                                :path-params {:name redirect-page-name}}))
                     (when (and contents-page?
                                (state/get-left-sidebar-open?))
                       (ui-handler/close-left-sidebar!)))}

src/main/frontend/db.cljs

@@ -50,7 +50,7 @@
   get-page-properties-content get-page-referenced-blocks get-page-referenced-pages get-page-unlinked-references
   get-pages get-pages-relation get-pages-that-mentioned-page get-public-pages get-tag-pages
   journal-page? local-native-fs? mark-repo-as-cloned! page-alias-set page-blocks-transform pull-block
-  set-file-last-modified-at! transact-files-db! with-block-refs-count get-modified-pages]
+  set-file-last-modified-at! transact-files-db! with-block-refs-count get-modified-pages page-empty? get-alias-source-page]
 
  [frontend.db.react
   get-current-marker get-current-page get-current-priority get-handler-keys set-file-content! set-key-value

src/main/frontend/db/model.cljs

@@ -798,6 +798,10 @@
      (db-utils/seq-flatten)
      (distinct))))
 
+(defn page-empty?
+  [repo page]
+  (nil? (:page/file (db-utils/entity repo [:page/name (string/lower-case page)]))))
+
 (defn get-pages-relation
   [repo with-journal?]
   (when-let [conn (conn/get-conn repo)]