Support custom locations request

[bennyyip]

This feature is for lsp server with custom locations request(e.g. ccls). It's similar to CocLocations in coc.nvim.

Example config for ccls

# not call
nmap <buffer> <localleader>f <scriptcmd>g:LspFindLocations('ccls', false, "textDocument/references", {"excludeRole": 32})<cr>
# macro
nmap <buffer> <localleader>M <scriptcmd>g:LspFindLocations('ccls', false, "textDocument/references", {"role": 64})<cr>
# read
nmap <buffer> <localleader>r <scriptcmd>g:LspFindLocations('ccls', false, "textDocument/references", {"role": 8})<cr>
# write
nmap <buffer> <localleader>w <scriptcmd>g:LspFindLocations('ccls', false, "textDocument/references", {"role": 16})<cr>
# x (xref)
# bases of up to 3 levels
nmap <buffer> <localleader>b <scriptcmd>g:LspFindLocations('ccls', false, "$ccls/inheritance", {})<cr>
nmap <buffer> <localleader>B <scriptcmd>g:LspFindLocations('ccls', false, "$ccls/inheritance", {"levels": 3})<cr>
# derived of up to 3 levels
nmap <buffer> <localleader>d <scriptcmd>g:LspFindLocations('ccls', false, "$ccls/inheritance", {"derived": v:true})<cr>
# derived of up to 3 levels
nmap <buffer> <localleader>D <scriptcmd>g:LspFindLocations('ccls', false, "$ccls/inheritance", {"derived": v:true, "levels": 3})<cr>
# caller
nmap <buffer> <localleader>c <scriptcmd>g:LspFindLocations('ccls', false, "$ccls/call")<cr>
# callee
nmap <buffer> <localleader>C <scriptcmd>g:LspFindLocations('ccls', false, "$ccls/call", {"callee": v:true})<cr>
# member
nmap <buffer> <localleader>m <scriptcmd>g:LspFindLocations('ccls', false, "$ccls/member")<cr>

[Shane-XB-Qian]

try the instr in 'lsp-cfg-customRequestHandlers', maybe that is your need.

[Shane-XB-Qian]

or if you just want to ignore some custom, then refer #386

[bennyyip]

@Shane-XB-Qian I want to use custom locations, not to ignore them.
If a lsp server supports custom locations, it probably supports references.

Can we specify a lsp server by name? For example, g:FindLocations('ccls', false, "$ccls/member")

[Shane-XB-Qian]

yes, you can customized add your request handler too, please check that example:

		vim9script
		g:LspAddServer([{
			filetype: ['javascript', 'typescript'],
			path: '/usr/local/bin/typescript-language-server',
			args: ['--stdio'],
			customNotificationHandlers: {
				'$/typescriptVersion': (lspserver, reply) => {
					echom printf("TypeScript Version = %s",
						reply.params.version)
				}
			}
		}])

in doc, or if not fit, then maybe need to refine this custom filter code.

[bennyyip]

lsp-custom-commands is about handling command from server to client.
This PR is about sending command from client to server.

[bennyyip]

Since custom command is only available in certain lsp server, I added buf.CurbufGetServerByName to specify it.

[Shane-XB-Qian]

`lsp-custom-commands` is about handling command **from server to client**. This PR is about sending command **from client to server**.

ohh, seems there is `CreateRequest()` func, but never used before, maybe didnot expect custom msg from client to server, so i donot know if should support or how to make it support better, e.g something like the one from server to client?

…

-- shane.xb.qian

[bennyyip]

CreateRequest() just constructs a request, and I don't think it's for end-user. This PR sends msg to server using lspserver.rpc().

[Shane-XB-Qian]

yes, i mean if like to support this feat, maybe began to use this CreateRequest() to constructs request.
normally the req to server were some fixed msg which defined in lsp spec,
as for custom, i have no such demand, and felt rare needing, let's see if yeggapa have some comment.

[Shane-XB-Qian]

yegappan accepted your PR, though maybe some tiny flaw, but not a big deal, it's ok.
//similar like others PR i reviewed here today, you maybe can refine it in the future..

[Shane-XB-Qian]

according to your example in the OP, looks your custom msg were not all for references, but do location related things, so:

1. the description here and next symbol.ShowLocations looks not accurate?
2. for now so-called 'custom request' actually only for 'location' related things.