add backpack export item

Author: JeremyGamer13

src/components/backpack/backpack.jsx

@@ -52,6 +52,7 @@ const Backpack = ({
     showMore,
     onToggle,
     onDelete,
+    onExport,
     onRename,
     onMouseEnter,
     onMouseLeave,
@@ -124,6 +125,7 @@ const Backpack = ({
                                         name={intl.formatMessage(labelMap[item.type])}
                                         selected={false}
                                         onClick={noop}
+                                        onExportButtonClick={item.type === 'script' ? null : onExport}
                                         onDeleteButtonClick={onDelete}
                                         // Currently, renaming sprites is not supported.
                                         onRenameButtonClick={item.type === 'sprite' ? null : onRename}
@@ -173,6 +175,7 @@ Backpack.propTypes = {
     intl: intlShape,
     loading: PropTypes.bool,
     onDelete: PropTypes.func,
+    onExport: PropTypes.func,
     onRename: PropTypes.func,
     onMore: PropTypes.func,
     onMouseEnter: PropTypes.func,

src/containers/backpack.jsx

@@ -19,6 +19,7 @@ import DropAreaHOC from '../lib/drop-area-hoc.jsx';
 
 import {connect} from 'react-redux';
 import storage from '../lib/storage';
+import downloadBlob from '../lib/download-blob';
 import VM from 'scratch-vm';
 
 const dragTypes = [DragConstants.COSTUME, DragConstants.SOUND, DragConstants.SPRITE];
@@ -39,6 +40,7 @@ class Backpack extends React.Component {
             'handleDrop',
             'handleToggle',
             'handleDelete',
+            'handleExport',
             'handleRename',
             'getBackpackAssetURL',
             'getContents',
@@ -174,6 +176,24 @@ class Backpack extends React.Component {
                 });
         });
     }
+    handleExport (id) {
+        const item = this.findItemById(id);
+        if (!item) return;
+        if (!item.bodyData) return;
+
+        const buffer = item.bodyData;
+        const blob = new Blob([buffer], { type: item.mime });
+
+        let recommendedName = item.name;
+        if (item.type === 'sprite') {
+            recommendedName += '.pms';
+        }
+        if (item.type === 'script') {
+            recommendedName += '.pmb';
+        }
+
+        downloadBlob(recommendedName, blob);
+    }
     findItemById (id) {
         return this.state.contents.find(i => i.id === id);
     }
@@ -270,6 +290,7 @@ class Backpack extends React.Component {
                 loading={this.state.loading}
                 showMore={this.state.moreToLoad}
                 onDelete={this.handleDelete}
+                onExport={this.handleExport}
                 onRename={this.handleRename}
                 onDrop={this.handleDrop}
                 onMore={this.handleMore}

src/lib/make-toolbox-xml.js

@@ -687,6 +687,21 @@ const control = function (isInitialSetup, isStage) {
         </block>
         ${blockSeparator}
         <block type="control_all_at_once"/>
+        <block type="control_run_as_sprite">
+            <value name="RUN_AS_OPTION">
+                <shadow type="control_run_as_sprite_menu"/>
+            </value>
+        </block>
+        ${blockSeparator}
+        <block type="control_try_catch"/>
+        <block type="control_throw_error">
+            <value name="ERROR">
+                <shadow type="text">
+                    <field name="TEXT">Hello!</field>
+                </shadow>
+            </value>
+        </block>
+        <block type="control_error"/>
         ${blockSeparator}
         <block type="control_backToGreenFlag"></block>
         <block type="control_stop_sprite">
@@ -696,12 +711,6 @@ const control = function (isInitialSetup, isStage) {
         </block>
         <block type="control_stop"/>
         ${blockSeparator}
-        <block type="control_run_as_sprite">
-            <value name="RUN_AS_OPTION">
-                <shadow type="control_run_as_sprite_menu"/>
-            </value>
-        </block>
-        ${blockSeparator}
         ${isStage ? `
             <block type="control_create_clone_of">
                 <value name="CLONE_OPTION">