Fix #1157: Tree: avoid duplicate rendering in _configureTreeColumn

This addresses cases where the same column definition object is passed
to one of the structure-related setters, as is the case when using
ColumnReorder.

Thanks to @dmartinzar for the bug report and original example + fix, and
@maier49 for the initial unit test.

Resolves #1185.

(Manually ported from 0f67fa1)

Tree.js

@@ -288,7 +288,35 @@ define([
 			// summary:
 			//		Adds tree navigation capability to a column.
 
-			var originalRenderCell = column.renderCell || this._defaultRenderCell;
+			if (!column._isConfiguredTreeColumn) {
+				var originalRenderCell = column.renderCell || this._defaultRenderCell;
+				column._isConfiguredTreeColumn = true;
+				column.renderCell = function (object, value, td, options) {
+					// summary:
+					//		Renders a cell that can be expanded, creating more rows
+
+					var grid = column.grid,
+						level = Number(options && options.queryLevel) + 1,
+						mayHaveChildren = !grid.collection.mayHaveChildren || grid.collection.mayHaveChildren(object),
+						expando, node;
+
+					level = grid._currentLevel = isNaN(level) ? 0 : level;
+					expando = column.renderExpando(level, mayHaveChildren,
+						grid._expanded[grid.collection.getIdentity(object)], object);
+					expando.level = level;
+					expando.mayHaveChildren = mayHaveChildren;
+
+					node = originalRenderCell.call(column, object, value, td, options);
+					if (node && node.nodeType) {
+						put(td, expando);
+						put(td, node);
+					}
+					else {
+						td.insertBefore(expando, td.firstChild);
+					}
+				};
+			}
+
 			var clicked; // tracks row that was clicked (for expand dblclick event handling)
 
 			this._treeColumn = column;
@@ -339,31 +367,6 @@ define([
 						grid.expand(this);
 					}));
 			}
-
-			column.renderCell = function (object, value, td, options) {
-				// summary:
-				//		Renders a cell that can be expanded, creating more rows
-
-				var grid = column.grid,
-					level = Number(options && options.queryLevel) + 1,
-					mayHaveChildren = !grid.collection.mayHaveChildren || grid.collection.mayHaveChildren(object),
-					expando, node;
-
-				level = grid._currentLevel = isNaN(level) ? 0 : level;
-				expando = column.renderExpando(level, mayHaveChildren,
-					grid._expanded[grid.collection.getIdentity(object)], object);
-				expando.level = level;
-				expando.mayHaveChildren = mayHaveChildren;
-
-				node = originalRenderCell.call(column, object, value, td, options);
-				if (node && node.nodeType) {
-					put(td, expando);
-					put(td, node);
-				}
-				else {
-					td.insertBefore(expando, td.firstChild);
-				}
-			};
 		},
 
 		_defaultRenderExpando: function (level, hasChildren, expanded) {

test/intern/mixins/Tree.js

@@ -355,6 +355,18 @@ define([
 					assert.isDefined(inputNode, 'Row ' + i + ' should have an input node');
 				}
 			});
+
+			// Test goal: ensure renderCell does not get re-wrapped over itself if the same column definition object
+			// is received during a column reset (e.g. via ColumnReorder).  See #1157
+			test.test('renderCell after same structure is recomputed', function () {
+				function countRowExpandos() {
+					return grid.row('0').element.querySelectorAll('.dgrid-expando-icon').length;
+				}
+
+				assert.strictEqual(countRowExpandos(), 1, 'Each parent row should have one expando icon');
+				grid.set('columns', grid.get('columns'));
+				assert.strictEqual(countRowExpandos(), 1,'Each parent row should still have only one expando icon');
+			});
 		});
 
 		test.suite('large family expansion without sort', function () {