Still problem with validation and Dynamic filled dropdowns

The issue I opened is closed, https://github.com/google/blockly/issues/2926 , so I open a new one. Hi, we tested with the last Blockly, 3.20191014.4, and we still have the problem with dynamic filled dropdowns.

An example to reproduce the problem with dynamic filled dropdown (in function of another dropdown value)

blockly_dyn_fields.zip (I used last blockly from today)

By doing this: using a function to fill FieldDropdown (with generateOptions a function)

this.appendDummyInput()
        .appendField(new Blockly.FieldDropdown(generateOptions), "FIELD_NAME");

then this error occurs:

Cannot set the dropdown's value to an unavailable option. Block type: test_dyn_field_field_block_type, Field name: FIELD_NAME, Value: SET2_FIELD3
Blockly.FieldDropdown.doClassValidation_ @ field_dropdown.js:420
Blockly.Field.setValue @ field.js:726
Blockly.Field.fromXml @ field.js:353
Blockly.Xml.domToField_ @ xml.js:802
Blockly.Xml.domToBlockHeadless_ @ xml.js:695
Blockly.Xml.domToBlockHeadless_ @ xml.js:733
Blockly.Xml.domToBlockHeadless_ @ xml.js:709
Blockly.Xml.domToBlock @ xml.js:544
Blockly.Xml.domToWorkspace @ xml.js:415
(anonymous) @ index.html:33

[BeksOmega]

Am I correct about this being the issue that didn’t work before?

I believe so yes. I think this was fixed when an explicit deserialization order was added. This change made it so that blocks are connected to their parents (but not children) before fields are deserialized. So now dynamic dropdowns can properly access the parent during deserialization.

Before, xml nodes were just processed in the order they appeared. Which mean fields were usually processed before blocks were connected to their parents. See the previous version.

[samelhusseini]

It’s unclear to me what the next steps are here. The problem is as follows: The user selects a dropdown option that is valid at the time, and so the FieldDropdown saves that value, which is then serialized to XML and saved as the field value. Later, when the XML is imported into Blockly, that option is no longer valid which doesn’t allow the value to be set, and outputs a warning.

We don’t provide a way to turn off that validation option (as it’s a class validator). @BeksOmega if you have some ideas.