Optionally fallback to goto_definition in lsp_symbol_definition

[timfjord]

Unfortunatelly not all LSPs have good symbol definition support. For example, solargraph(ruby) has limited support and quite offten returns No results found, so you have to keep and remember the built-in Sublime goto_definition key bining to be able to jump to at least something.
It becomes especially inconvenient when you switch between different programming langages where one has a better symbol defition support than another so you always have to keep in mind what exact key to use.

This PR adds an optional fallback parameter to the lsp_symbol_definition command that allows to fallback to the built-in goto_definition command in case no results were found.

{ "keys": ["super+alt+down"], "command": "goto_definition" },
{
  "keys": ["super+alt+down"],
  "command": "lsp_symbol_definition",
  "args": { "side_by_side": false, "fallback": true },
  "context": [
    {
      "key": "lsp.session_with_capability",
      "operator": "equal",
      "operand": "definitionProvider"
    },
    {
      "key": "auto_complete_visible",
      "operator": "equal",
      "operand": false
    }
  ]
},

This option allows you to have more consistant key bining and better integration with Sublime, because you don't need to worry if LSP is enable or no, as every time it would try to find at least something.

[rchl]

• Would be good to mention something about that in https://lsp.sublimetext.io/features/#goto-definition also.
• The default keybindings should be updated to include this argument (disabled by default) for visibility.

[timfjord]

@rchl I've addressed your suggestions.
Please let me know if the doc update makes sense for you, otherwise I will come up with something else

[jwortmann]

I wonder whether this shouldn't be made the default behavior? (I.e. use default value fallback: bool = True in the argument list.)
Then we could even consider to enable the F12 keybinding for lsp_symbol_definition, which is currently commented out.

Otherwise, users need to override the resource files Context.sublime-menu & Main.sublime-menu if they want to make use of this improvement. And probably not many people read the documentation or keep up to date with the newly added features.

[timfjord]

If we want to make the fallback true by default, we might need to update the status with something like No results found, falling back to the built-in Goto Definition to let the user know what is happening under the hood

[rchl]

I'm not 100% sure but would lean towards enabling fallback and the LSP key binding for F12 by default.

Adding the status message on fallback is not a bad idea (although myself I probably wouldn't notice it anyway).