Special characters escaped in text block

[Bart Butenaers]

Hi folks,

Got a question from one of our users, who wants to generate a (Javascript) string containing termination characters (newline, carriage return, tabs, ...).

Currently these characters seem to be automatically escaped by the text block (i.e. extra \ prefix):

Seems the text-block always applies escaping (via the 'quote_' function):

I'm wondering why these are always escaped, and if there is a (good) way to avoid this?

Thanks !

Bart

[Amber Blaylock]

We actually ran into this in our setup. It seems like this is done automatically in Blockly. Our solution was just to make a special character block and add it in where needed using string concatenation. If you want to just wholesale borrow that solution, the code is here:

Blockly.Blocks['meta_characters'] = {
 init: function () {
 this.setOutput(true, 'String');
 this.appendDummyInput('')
 .appendField('Special character:')
 .appendField(new Blockly.FieldDropdown([['Line Feed (\\n)', '\\n'], ['Carriage Return (\\r)', '\\r'], ['Carriage Return Line Feed (\\r\\n)', '\\r\\n'], ['Tab (\\t)', '\\t']]), 'character');
 this.setColour(Blockly.Msg.TEXTS_HUE ? Blockly.Msg.TEXTS_HUE : Blockly.Blocks.texts.HUE);
 this.setTooltip('');
 this.setHelpUrl('');
 }
};

Blockly.JavaScript['meta_characters'] = function (block) {
 var code = '\'' + (block.getFieldValue('character') || '') + '\'';
 return [code, Blockly.JavaScript.ORDER_ATOMIC];
};

[Amber Blaylock]

As for why it's done, I believe that it's meant to prevent wise alecs from entering escaping sequences into a text block and forcing anything that executes the code from injecting arbitrary code of their own design.

[Bart Butenaers]

Hi Amber,

Thanks a lot for sharing your solution !!

Your 'why' explanation also makes sense.

Kind regards,

Bart