Run code actions on save

[jrieken]

Now that we have added code action kinds we could denote them to run on save. Similar to the new command a new setting could exists, e.g. editor.onSaveCodeaction: [quickfix.cleanup, etc.]

[mjbvz]

A few potential designs for this feature:

editor.onSaveCodeaction User Setting

Add a user setting that lists code action kinds that should be run on save.

Pro

• Easily customizable by user.
• Does not require extensions to adopt any new APIs

Con

• The setting is not very discoverable or easy to explain.
• What should the default value be?
• What if java want organize imports to be run on save but typescript does not? (I know you can use "[java]": { "editor.onSaveCodeaction": [...]})

Add a new CodeAction.runOnSave property

Add a runOnSave property to the CodeAction class. Use this property to determine which code actions to run on save

Pro

• Lets extensions fully control which actions should be run on save
• The runOnSave property could be controlled by a more explicit setting such as "typescript.organizeImports.runOnSave": true

Con

• Requires extension adoption
• Could lead to lots of extension specific settings such as, "typescript.organizeImports.runOnSave": true

Other open questions

• How do we handle multiple code actions that should be run on save? These may return conflicting edits

[jrieken]

I think I'd prefer option 1. We could help with the discoverability by adding the predefined code action kinds to the json-schema. It's also more similar to the keybindings story we have around code actions.