fix(GridColumn): Allow for duplicate field coldefs

If two column definitions were supplied with the same field and no name
property, it was causing conflicts as names need to be unique.

The default behavior now will just add an incrementing number on to the
end of extra columns, starting with "2".

Fixes #2364

src/js/core/factories/Grid.js

@@ -622,19 +622,18 @@ angular.module('ui.grid')
       var columnCache = self.columns.slice(0);
 
       // We need to allow for the "row headers" when mapping from the column defs array to the columns array
-      //   If we have a row header in columns[0] and don't account for it we'll overwrite it with the column in columnDefs[0]
-      var rowHeaderOffset = self.rowHeaderColumns.length;
+      //   If we have a row header in columns[0] and don't account for it   we'll overwrite it with the column in columnDefs[0]
 
       // Go through all the column defs
       for (i = 0; i < self.options.columnDefs.length; i++) {
         // If the column at this index has a different name than the column at the same index in the column defs...
-        if (self.columns[i + rowHeaderOffset].name !== self.options.columnDefs[i].name) {
+        if (self.columns[i + headerOffset].name !== self.options.columnDefs[i].name) {
           // Replace the one in the cache with the appropriate column
-          columnCache[i + rowHeaderOffset] = self.getColumn(self.options.columnDefs[i].name);
+          columnCache[i + headerOffset] = self.getColumn(self.options.columnDefs[i].name);
         }
         else {
           // Otherwise just copy over the one from the initial columns
-          columnCache[i + rowHeaderOffset] = self.columns[i + rowHeaderOffset];
+          columnCache[i + headerOffset] = self.columns[i + headerOffset];
         }
       }
 
@@ -738,14 +737,59 @@ angular.module('ui.grid')
    * validates that name or field is present
    */
   Grid.prototype.preprocessColDef = function preprocessColDef(colDef) {
+    var self = this;
+
     if (!colDef.field && !colDef.name) {
       throw new Error('colDef.name or colDef.field property is required');
     }
 
     //maintain backwards compatibility with 2.x
     //field was required in 2.x.  now name is required
     if (colDef.name === undefined && colDef.field !== undefined) {
-      colDef.name = colDef.field;
+      // See if the column name already exists:
+      var foundName = self.getColumn(colDef.field);
+
+      // If a column with this name already  exists, we will add an incrementing number to the end of the new column name
+      if (foundName) {
+        // Search through the columns for names in the format: <name><1, 2 ... N>, i.e. 'Age1, Age2, Age3',
+        var nameRE = new RegExp('^' + colDef.field + '(\\d+)$', 'i');
+
+        var foundColumns = self.columns.filter(function (column) {
+          // Test against the displayName, as that's what'll have the incremented number
+          return nameRE.test(column.displayName);
+        })
+        // Sort the found columns by the end-number
+        .sort(function (a, b) {
+          if (a === b) {
+            return 0;
+          }
+          else {
+            var numA = a.match(nameRE)[1];
+            var numB = b.match(nameRE)[1];
+
+            return parseInt(numA, 10) > parseInt(numB, 10) ? 1 : -1;
+          }
+        });
+
+        // Not columns found, so start with number "2"
+        if (foundColumns.length === 0) {
+          colDef.name = colDef.field + '2';
+        }
+        else {
+          // Get the number from the final column
+          var lastNum = foundColumns[foundColumns.length-1].displayName.match(nameRE)[1];
+
+          // Make sure to parse to an int
+          lastNum = parseInt(lastNum, 10);
+
+          // Add 1 to the number from the last column and tack it on to the field to be the name for this new column 
+          colDef.name = colDef.field + (lastNum + 1);
+        }
+      }
+      // ... otherwise just use the field as the column name
+      else {
+        colDef.name = colDef.field;
+      }
     }
 
   };

test/unit/core/factories/GridColumn.spec.js

@@ -71,6 +71,49 @@ describe('GridColumn factory', function () {
     it('should obey columnDef sort spec', function () {
       // ... TODO(c0bra)
     });
+
+    describe('when handling field-only defs', function () {
+      beforeEach(function () {
+        grid = new Grid({ id: 1 });
+        grid.registerColumnBuilder(gridClassFactory.defaultColumnBuilder);
+      });
+
+      it('should add an incrementing number to column names when they have the same field and no name', function () {
+        var cols = [
+          { field: 'age' },
+          { field: 'name' },
+          { field: 'name' },
+          { field: 'name' }
+        ];
+
+        grid.options.columnDefs = cols;
+
+        buildCols();
+
+        expect(grid.columns[0].displayName).toEqual('Age');
+        expect(grid.columns[1].displayName).toEqual('Name');
+        expect(grid.columns[2].displayName).toEqual('Name2');
+        expect(grid.columns[3].displayName).toEqual('Name3');
+      });
+
+      it('should account for existing incremented names', function () {
+        var cols = [
+          { field: 'age' },
+          { field: 'name' },
+          { field: 'name', name: 'Name3' },
+          { field: 'name' }
+        ];
+
+        grid.options.columnDefs = cols;
+
+        buildCols();
+
+        expect(grid.columns[0].displayName).toEqual('Age');
+        expect(grid.columns[1].displayName).toEqual('Name');
+        expect(grid.columns[2].displayName).toEqual('Name3');
+        expect(grid.columns[3].displayName).toEqual('Name4');
+      });
+    });
   });
 
   describe('getRenderContainer', function () {