Check if a type exists before testing instanceof (#3031)

* Check if a type exists before instance of

core/block.js

@@ -1338,11 +1338,7 @@ Blockly.Block.prototype.toString = function(opt_maxLength, opt_emptyToken) {
   } else {
     for (var i = 0, input; input = this.inputList[i]; i++) {
       for (var j = 0, field; field = input.fieldRow[j]; j++) {
-        if (field instanceof Blockly.FieldDropdown && !field.getValue()) {
-          text.push(emptyFieldPlaceholder);
-        } else {
-          text.push(field.getText());
-        }
+        text.push(field.getText());
       }
       if (input.connection) {
         var child = input.connection.targetBlock();

core/block_svg.js

@@ -632,8 +632,7 @@ Blockly.BlockSvg.prototype.createTabList_ = function() {
   var list = [];
   for (var i = 0, input; input = this.inputList[i]; i++) {
     for (var j = 0, field; field = input.fieldRow[j]; j++) {
-      if (field instanceof Blockly.FieldTextInput && field.isVisible()) {
-        // TODO (#1276): Also support dropdown fields.
+      if (field.isTabNavigable() && field.isVisible()) {
         list.push(field);
       }
     }

core/field.js

@@ -913,6 +913,22 @@ Blockly.Field.prototype.getParentInput = function() {
   return parentInput;
 };
 
+/**
+ * Returns whether or not we should flip the field in RTL.
+ * @return {boolean} True if we should flip in RTL.
+ */
+Blockly.Field.prototype.getFlipRtl = function() {
+  return false;
+};
+
+/**
+ * Returns whether or not the field is tab navigable.
+ * @return {boolean} True if the field is tab navigable.
+ */
+Blockly.Field.prototype.isTabNavigable = function() {
+  return false;
+};
+
 /**
  * Handles the given action.
  * This is only triggered when keyboard accessibility mode is enabled.

core/field_colour.js

@@ -35,6 +35,7 @@ goog.require('Blockly.utils.aria');
 goog.require('Blockly.utils.colour');
 goog.require('Blockly.utils.dom');
 goog.require('Blockly.utils.IdGenerator');
+goog.require('Blockly.utils.KeyCodes');
 goog.require('Blockly.utils.object');
 goog.require('Blockly.utils.Size');
 

core/field_image.js

@@ -218,6 +218,7 @@ Blockly.FieldImage.prototype.doValueUpdate_ = function(newValue) {
 /**
  * Get whether to flip this image in RTL
  * @return {boolean} True if we should flip in RTL.
+ * @override
  */
 Blockly.FieldImage.prototype.getFlipRtl = function() {
   return this.flipRtl_;

core/field_textinput.js

@@ -35,6 +35,7 @@ goog.require('Blockly.utils');
 goog.require('Blockly.utils.aria');
 goog.require('Blockly.utils.Coordinate');
 goog.require('Blockly.utils.dom');
+goog.require('Blockly.utils.KeyCodes');
 goog.require('Blockly.utils.object');
 goog.require('Blockly.utils.Size');
 goog.require('Blockly.utils.userAgent');
@@ -357,15 +358,14 @@ Blockly.FieldTextInput.prototype.unbindInputEvents_ = function() {
  * @protected
  */
 Blockly.FieldTextInput.prototype.onHtmlInputKeyDown_ = function(e) {
-  var tabKey = 9, enterKey = 13, escKey = 27;
-  if (e.keyCode == enterKey) {
+  if (e.keyCode == Blockly.utils.KeyCodes.ENTER) {
     Blockly.WidgetDiv.hide();
     Blockly.DropDownDiv.hideWithoutAnimation();
-  } else if (e.keyCode == escKey) {
+  } else if (e.keyCode == Blockly.utils.KeyCodes.ESC) {
     this.htmlInput_.value = this.htmlInput_.defaultValue;
     Blockly.WidgetDiv.hide();
     Blockly.DropDownDiv.hideWithoutAnimation();
-  } else if (e.keyCode == tabKey) {
+  } else if (e.keyCode == Blockly.utils.KeyCodes.TAB) {
     Blockly.WidgetDiv.hide();
     Blockly.DropDownDiv.hideWithoutAnimation();
     this.sourceBlock_.tab(this, !e.shiftKey);
@@ -479,6 +479,15 @@ Blockly.FieldTextInput.nonnegativeIntegerValidator = function(text) {
   return n;
 };
 
+/**
+ * Returns whether or not the field is tab navigable.
+ * @return {boolean} True if the field is tab navigable.
+ * @override
+ */
+Blockly.FieldTextInput.prototype.isTabNavigable = function() {
+  return true;
+};
+
 /**
  * Use the `getText_` developer hook to override the field's text representation.
  * When we're currently editing, return the current html value instead.

core/renderers/measurables/row_elements.js

@@ -95,7 +95,7 @@ Blockly.blockRendering.Field = function(constants, field, parentInput) {
   Blockly.blockRendering.Field.superClass_.constructor.call(this, constants);
   this.field = field;
   this.isEditable = field.isCurrentlyEditable();
-  this.flipRtl = field instanceof Blockly.FieldImage && field.getFlipRtl();
+  this.flipRtl = field.getFlipRtl();
   this.type |= Blockly.blockRendering.Types.FIELD;
 
   var size = this.field.getSize();