leverage PATH for locating local executables (#283)

1. This is a breaking change for the following servers, which will have to be
reinstalled:

 - ltex
 - clangd

2. This is a breaking change for users who reach into the default options (for
   example via server:get_default_options()) to access the `cmd` property.
   nvim-lsp-installer no longer provides the `cmd` (except in a few
   instances), but instead provides an amended PATH which allows neovim's LSP
   client to locate the locally installed executable.

   To access the `cmd`, simply access it via lspconfig instead, for example
   like so:

    local default_config = require("lspconfig.server_configurations.rust_analyzer").default_config
    print("I can now access the cmd governed by lspconfig:", default_config.cmd)

3. This is a breaking change for 3rd party use cases that makes use of the
   `executable()` APIs (e.g., `npm.executable(root_dir, "tsserver")`). The
   recommended usage is to instead to use the canonical name of the command
   ("tsserver"), while providing an amended PATH, for example:

    local npm = require("nvim-lsp-installer.installers.npm")
    local server = server.Server:new {
        ...,
        root_dir = root_dir,
        installer = npm.packages { "tsserver" },
        default_options = {
            cmd = { "tsserver" },
            cmd_env = npm.env(root_dir),
        }
    }

1 files changed, 6 insertions, 1 deletions

diff --git a/lua/nvim-lsp-installer/servers/sumneko_lua/init.lua b/lua/nvim-lsp-installer/servers/sumneko_lua/init.lua
index 907545be..1d562bb4 100644
--- a/lua/nvim-lsp-installer/servers/sumneko_lua/init.lua
+++ b/lua/nvim-lsp-installer/servers/sumneko_lua/init.lua
@@ -4,6 +4,7 @@ local platform = require "nvim-lsp-installer.platform"
 local Data = require "nvim-lsp-installer.data"
 local std = require "nvim-lsp-installer.installers.std"
 local context = require "nvim-lsp-installer.installers.context"
+local process = require "nvim-lsp-installer.process"
 
 local coalesce, when = Data.coalesce, Data.when
 
@@ -40,7 +41,11 @@ return function(name, root_dir)
             end),
         },
         default_options = {
-            cmd = { path.concat { root_dir, "extension", "server", "bin", "lua-language-server" } },
+            cmd_env = {
+                PATH = process.extend_path {
+                    path.concat { root_dir, "extension", "server", "bin" },
+                },
+            },
         },
     }
 end