Opening dropdown in a block in the flyout and switching categories causes js error

[picklesrus]

When switching categories when a dropdown is open you get the following js error:

vertical.js:2842 Uncaught TypeError: Cannot read property 'isShadow' of null
at Blockly.FieldDropdown.onHide (vertical.js:2842)
at Function.Blockly.DropDownDiv.hide (vertical.js:2462)
at Blockly.Toolbox. (vertical.js:2973)
at HTMLDivElement.g (vertical.js:2784)

Steps to Reproduce

0. open js console.
1. Open motion category
2. Open dropdown in the "point toward" block
3. Without closing the dropdown , click on the "Events" category (probably others too).
4. see error.

Operating System and Browser

Chrome MacOS

[Tymewalk]

Just confirmed it here. Firefox 50.1.0, Ubuntu 16.04 LTS.

JS console dump:

TypeError: this.sourceBlock_ is null[Learn More] field_dropdown.js:240:1
	Blockly.FieldDropdown.prototype.onHide https://llk.github.io/scratch-blocks/playgrounds/core/field_dropdown.js:240:1
	bound  self-hosted
	Blockly.DropDownDiv.hide https://llk.github.io/scratch-blocks/playgrounds/core/dropdowndiv.js:381:5
	Blockly.Toolbox.prototype.init/< https://llk.github.io/scratch-blocks/playgrounds/core/toolbox.js:119:9
	Blockly.bindEventWithChecks_/wrapFunc https://llk.github.io/scratch-blocks/playgrounds/core/blockly.js:455:9

It happens across all categories and also happens with the color selection tool (on some of the pen and sensing blocks).

I haven't actually looked, but I think this is because the "hide" function is trying to reference an object which no longer exists (due to it being removed when the other category was opened).

[mrjacobbloom]

This does not happen with the dropdown when you click a reporter to see its value

[Tymewalk]

@Airhogs777 It happens for me. What OS/Browser are you using?

(Console dump upon trying it:)

Blockly.FieldDropdown.prototype.onHide https://llk.github.io/scratch-blocks/playgrounds/core/field_dropdown.js:240:1
	bound  self-hosted
	Blockly.DropDownDiv.hideWithoutAnimation https://llk.github.io/scratch-blocks/playgrounds/core/dropdowndiv.js:402:5
	Blockly.DropDownDiv.hide/Blockly.DropDownDiv.animateOutTimer_< https://llk.github.io/scratch-blocks/playgrounds/core/dropdowndiv.js:378:5

When the blocks are dragged onto the workspace, changing categories causes them to close, as expected.

We probably need a check to see if the object is still visible before attempting to hide it.

[mrjacobbloom]

@Tymewalk Chrome on Win10 on scratch-gui

[Tymewalk]

@Airhogs777 Strange, I just tested there, and it still happens.

Might be something to do with Firefox?

[Tymewalk]

Not sure if that commit was actually intended to be referenced, but the problem still exists on the vertical playground. (Unless that hasn't been updated.)

[Tymewalk]

This is where the error is happening: if (this.sourceBlock_.isShadow()) {

I'm looking to see if I can get a more detailed message now.

EDIT: This may also help in the event we need to add a check to see if the block still exists.

[Tymewalk]

After replicating this glitch, another one happens:

How to Replicate

• Replicate this glitch as described above.
• Drag a block onto the playground.
• Attempt to drag the background.

Expected Output

The stage pans so you can see other blocks.

What Actually Happens

This error is thrown:

TypeError: this.sourceBlock_ is null[Learn More] field_dropdown.js:240:1
	Blockly.FieldDropdown.prototype.onHide https://llk.github.io/scratch-blocks/playgrounds/core/field_dropdown.js:240:1
	bound  self-hosted
	Blockly.DropDownDiv.hide https://llk.github.io/scratch-blocks/playgrounds/core/dropdowndiv.js:381:5
	Blockly.WorkspaceSvg.prototype.onMouseDown_ https://llk.github.io/scratch-blocks/playgrounds/core/workspace_svg.js:1007:3
	Blockly.bindEventWithChecks_/wrapFunc https://llk.github.io/scratch-blocks/playgrounds/core/blockly.js:455:9

and the stage does not pan.