lua LSP client: initial implementation (#11336)

Mainly configuration and RPC infrastructure can be considered "done". Specific requests and their callbacks will be improved later (and also served by plugins). There are also some TODO:s for the client itself, like incremental updates.

Co-authored by at-tjdevries and at-h-michael, with many review/suggestion contributions.

runtime/lua/vim/uri.lua

@@ -0,0 +1,89 @@
+--- TODO: This is implemented only for files now.
+-- https://tools.ietf.org/html/rfc3986
+-- https://tools.ietf.org/html/rfc2732
+-- https://tools.ietf.org/html/rfc2396
+
+
+local uri_decode
+do
+  local schar = string.char
+  local function hex_to_char(hex)
+    return schar(tonumber(hex, 16))
+  end
+  uri_decode = function(str)
+    return str:gsub("%%([a-fA-F0-9][a-fA-F0-9])", hex_to_char)
+  end
+end
+
+local uri_encode
+do
+  local PATTERNS = {
+    --- RFC 2396
+    -- https://tools.ietf.org/html/rfc2396#section-2.2
+    rfc2396 = "^A-Za-z0-9%-_.!~*'()";
+    --- RFC 2732
+    -- https://tools.ietf.org/html/rfc2732
+    rfc2732 = "^A-Za-z0-9%-_.!~*'()[]";
+    --- RFC 3986
+    -- https://tools.ietf.org/html/rfc3986#section-2.2
+    rfc3986 = "^A-Za-z0-9%-._~!$&'()*+,;=:@/";
+  }
+  local sbyte, tohex = string.byte
+  if jit then
+    tohex = require'bit'.tohex
+  else
+    tohex = function(b) return string.format("%02x", b) end
+  end
+  local function percent_encode_char(char)
+    return "%"..tohex(sbyte(char), 2)
+  end
+  uri_encode = function(text, rfc)
+    if not text then return end
+    local pattern = PATTERNS[rfc] or PATTERNS.rfc3986
+    return text:gsub("(["..pattern.."])", percent_encode_char)
+  end
+end
+
+
+local function is_windows_file_uri(uri)
+  return uri:match('^file:///[a-zA-Z]:') ~= nil
+end
+
+local function uri_from_fname(path)
+  local volume_path, fname = path:match("^([a-zA-Z]:)(.*)")
+  local is_windows = volume_path ~= nil
+  if is_windows then
+    path = volume_path..uri_encode(fname:gsub("\\", "/"))
+  else
+    path = uri_encode(path)
+  end
+  local uri_parts = {"file://"}
+  if is_windows then
+    table.insert(uri_parts, "/")
+  end
+  table.insert(uri_parts, path)
+  return table.concat(uri_parts)
+end
+
+local function uri_from_bufnr(bufnr)
+  return uri_from_fname(vim.api.nvim_buf_get_name(bufnr))
+end
+
+local function uri_to_fname(uri)
+  -- TODO improve this.
+  if is_windows_file_uri(uri) then
+    uri = uri:gsub('^file:///', '')
+    uri = uri:gsub('/', '\\')
+  else
+    uri = uri:gsub('^file://', '')
+  end
+
+  return uri_decode(uri)
+end
+
+return {
+  uri_from_fname = uri_from_fname,
+  uri_from_bufnr = uri_from_bufnr,
+  uri_to_fname = uri_to_fname,
+}
+-- vim:sw=2 ts=2 et