make the ArangoShell refill its collection cache (#3441)

CHANGELOG

@@ -1,6 +1,16 @@
 devel
 -----
 
+* make the ArangoShell refill its collection cache when a yet-unknown collection
+  is first accessed. This fixes the following problem:
+
+      arangosh1> db._collections();  // shell1 lists all collections
+      arangosh2> db._create("test"); // shell2 now creates a new collection 'test'
+      arangosh1> db.test.insert({}); // shell1 is not aware of the collection created
+                                     // in shell2, so the insert will fail
+
+* make AQL `DISTINCT` not change the order of the results it is applied on
+
 * enable JEMalloc background thread for purging and returning unused memory
   back to the operating system (Linux only)
 

js/client/modules/@arangodb/arango-database.js

@@ -302,7 +302,7 @@ ArangoDatabase.prototype._collections = function () {
 
 ArangoDatabase.prototype._collection = function (id) {
   if (typeof id !== 'number' &&
-      this[id] && this[id] instanceof this._collectionConstructor) {
+      this.hasOwnProperty(id) && this[id] && this[id] instanceof this._collectionConstructor) {
     return this[id];
   }
   var url;

js/client/modules/@arangodb/index.js

@@ -90,7 +90,17 @@ exports.ArangoView = require('@arangodb/arango-view').ArangoView;
 if (typeof internal.arango !== 'undefined') {
   try {
     exports.arango = internal.arango;
-    exports.db = new exports.ArangoDatabase(internal.arango);
+    let db = new exports.ArangoDatabase(internal.arango);
+    // proxy the db object, so we can track access to non-existing collections
+    exports.db = new Proxy(db, {
+      get(target, name) {
+        if (!target.hasOwnProperty(name) && target[name] === undefined && typeof name === 'string') {
+          // unknown collection, try re-populating the cache
+          db._collections();
+        }
+        return target[name];
+      },
+    });
     internal.db = exports.db; // TODO remove
   } catch (err) {
     internal.print('cannot connect to server: ' + String(err));