Merge pull request #340 from captainsafia/merge-cell-fix

Added fix for merge above on topmost cell to resolve #330

notebook/static/notebook/js/notebook.js

@@ -1445,6 +1445,13 @@ define(function (require) {
         if (indices.length <= 1) {
             return;
         }
+
+        // Check if trying to merge above on topmost cell or wrap around
+        // when merging above, see #330
+        if (indices.filter(function(item) {return item < 0}).length > 0) {
+            return;
+        }
+
         for (var i=0; i < indices.length; i++) {
             if (!this.get_cell(indices[i]).is_mergeable()) {
                 return;

notebook/tests/notebook/dualmode_merge.js

@@ -67,6 +67,21 @@ casper.notebook_test(function () {
         this.test.assert(cell_is_mergeable(2), 'Cell 2 is mergeable');
     });
 
+    // Try to merge cell 0 above, nothing should happen
+    this.then(function () {
+        this.select_cell(0);
+    });
+    this.thenEvaluate(function() {
+        IPython.notebook.merge_cell_above();
+    });
+    this.then(function() {
+        this.test.assertEquals(this.get_cells_length(), 3, 'Merge cell 0 above: There are still 3 cells');
+        this.test.assertEquals(this.get_cell_text(0), a, 'Merge cell 0 above: Cell 0 is unchanged');
+        this.test.assertEquals(this.get_cell_text(1), b, 'Merge cell 0 above: Cell 1 is unchanged');
+        this.test.assertEquals(this.get_cell_text(2), c, 'Merge cell 0 above: Cell 2 is unchanged');
+        this.validate_notebook_state('merge up', 'command', 0);
+    });
+
     // Try to merge cell 0 below with cell 1
     this.then(function () {
         this.select_cell(0);