Extensionification: All blocks should be implemented using extension system

[cwillisf]

Extensionification!

Goals

• All blocks in Scratch 3.0 should be entirely defined within scratch-vm. Adding a new block should not require modifications in scratch-gui or scratch-blocks.
• All blocks in Scratch 3.0 should be implemented in the same way. We should not maintain two (or more) different ways to define blocks.
• The extension system should be enhanced such that it becomes powerful enough to implement every existing Scratch 3.0 block.

Tasks

• Supporting features
  • Extensions should be able to place buttons in the toolbox
  • Extension blocks should refresh when changing targets
  • Extension blocks should refresh on certain actions (create/update/delete variable, list, procedure, message, etc.)
  • Extensionified categories can be interleaved with categories defined in scratch-gui's makeToolboxXML
• Serialization
  • Existing SB3 files, including those containing variables, lists, or custom procedures, can be loaded correctly when those categories are extensionified.
  • An SB3 file saved with extensionified variables, lists, or custom procedures can be loaded correctly in an older editor (esp. Scratch Desktop).
• Categories
  • Motion
  • Looks
  • Sound
  • Events (including broadcast _ & friends)
  • Control (including stop _)
  • Sensing (including _ of _)
  • Operators
  • Variables
  • My Blocks

[harbaum]

One of the most basic features for this is the support for translations. Currently these are in scratch-blocks/msg/messages.js and the translation system supposed to be there doesn't seem to be functional at all.

[cwillisf]

@harbaum we actually have a separate translation system for Scratch extensions. We're still figuring out the details but documentation on the current iteration is available here and will be updated as we progress:
https://github.com/LLK/scratch-vm/blob/develop/docs/extensions.md#translation

[harbaum]

Yes, i know. I tried to use it but it had no effect. I then searched the code and found no code that would care for these translations.