Add support for opening source generated documents

[zickb]

This PR adds support for opening and handling source generated documents. The reloading of open source generated documents is currently not implement, but should not be to hard to add.

The "BufReadCmd" callback is inspired by https://github.com/mfussenegger/nvim-jdtls/blob/master/lua/jdtls.lua#L1186 (including the vim.wait call).

The VsCode extension has also added support for source generated documents. (initial: dotnet/vscode-csharp#7581, refresh support: dotnet/vscode-csharp#7791, src location: `https://github.com/dotnet/vscode-csharp/blob/main/src/lsptoolshost/sourceGeneratedFilesContentProvider.ts)

Notes from manual testing:
The VsCode extension and this extension returns some times different results when executing the "go to reference" command.
E.g. In VsCode 3 references are found (t.Print(), public partial Regex Print(); and public partial global::System.Text.RegularExpressions.Regex Print() => global::System.Text.RegularExpressions.Generated.Print_0.Instance;)
while this extension only returns 2 references (public partial Regex Print(); and public partial global::System.Text.RegularExpressions.Regex Print() => global::System.Text.RegularExpressions.Generated.Print_0.Instance;).
But if the cursor is at the source generate method name, VsCode and this extension returns both 3 references.

I guess that this is not a direct problem with this PR, but rather some difference in the lsp client setup/lsp client implementation that lead to this behavior.

var t = new Test2();
t.Print();
//  ^ place cursor here

public partial class Test2
{
	[GeneratedRegex("test")]
	public partial Regex Print();

	[GeneratedRegex("test2")]
	public partial Regex Print2();
}

---

For a better telescope support two thinks must be done:

1. register an autocmd handler:

vim.api.nvim_create_autocmd({ "User" }, {
	pattern = "TelescopePreviewerLoaded",
	callback = function(args)
		local putils = require("telescope.previewers.utils")
		if args.data ~= nil and args.data.bufname ~= nil and args.data.bufname:match("^roslyn%-source%-generated://") then
			putils.highlighter(args.buf, 'cs', {})
		end
	end

2. a slightly customized entry_maker function have to be provided:

local get_filename_fn = function()
	local bufnr_name_cache = {}
	return function(bufnr)
		bufnr = vim.F.if_nil(bufnr, 0)
		local c = bufnr_name_cache[bufnr]
		if c then
			return c
		end

		local n = vim.api.nvim_buf_get_name(bufnr)
		bufnr_name_cache[bufnr] = n
		return n
	end
end

local gen_from_quickfix_with_remotefile_support = function(opts)
	opts = opts or {}
	local show_line = vim.F.if_nil(opts.show_line, true)

	local utils = require("telescope.utils")
	local make_entry = require("telescope.make_entry")
	local hidden = utils.is_path_hidden(opts)

	local make_display = function(entry)
		-- optional customization
		local filename = entry.filename:match("^roslyn%-source%-generated://(.+)%?")
		if filename == nil then
			filename = entry.filename
		end

		local display_filename, path_style = utils.transform_path(opts, filename)

		local display_string = string.format("%s:%d:%d", display_filename, entry.lnum, entry.col)
		if hidden then
			display_string = string.format("%4d:%2d", entry.lnum, entry.col)
		end

		if show_line then
			local text = entry.text
			if opts.trim_text then
				text = vim.trim(text)
			end
			text = text:gsub(".* | ", "")
			display_string = display_string .. ":" .. text
		end

		return display_string, path_style
	end

	local get_filename = get_filename_fn()

	return function(entry)
		local filename = vim.F.if_nil(entry.filename, get_filename(entry.bufnr))

		-- required: Custom language server protocol extensions can result in servers sending URIs with custom schemes.
		-- These files are not stored on disk and we need to set the buffer number to show a preview for the buffer content.
		local bufnr = entry.bufnr
		if filename:match("^roslyn%-source%-generated://") then
			bufnr = vim.fn.bufnr(filename)
		end

		return make_entry.set_default_entry_mt({
			value = entry,
			ordinal = (not hidden and filename or "") .. " " .. entry.text,
			display = make_display,
			bufnr = bufnr,
			filename = filename,
			lnum = entry.lnum,
			col = entry.col,
			text = entry.text,
			start = entry.start,
			finish = entry.finish,
		}, opts)
	end
end

local opts = {
       entry_maker = gen_from_quickfix_with_remotefile_support()
}

require("telescope.builtin").lsp_references(opts)

[seblj]

Wow this looks great! Thank you very much!

I just had one question, and otherwise I just want to test it a little bit first.

The code looks very simple and is easily understandable🙌

[seblj]

If I understand it correctly, we only set modified here to be able to set the lines in the handler, and then immediately set it to nomodifiable again after that?

Is it possible to set it to modifiable just before setting the lines inside the handler or doesn't that work?

[seblj]

I see that this is also done for the jdtls, so it is probably fine🤷‍♂️ I was just curious

[seblj]

I just tried it a bit, and seems good👍 I just added a commit to format the code while I was already having it open and format on save is turned on for me

[seblj]

Thanks!