rewrite some installers for broader cross-platform support (#85)

- Remove all usage of zx in favour of native Lua (via libuv)
- Introduce new set of `std` installers

The following servers will have to be reinstalled due to this change:
1. clangd
2. solargraph
3. sumneko_lua
4. tailwindcss

1 files changed, 40 insertions, 18 deletions

diff --git a/lua/nvim-lsp-installer/installers/init.lua b/lua/nvim-lsp-installer/installers/init.lua
index 98bb78bc..7698e900 100644
--- a/lua/nvim-lsp-installer/installers/init.lua
+++ b/lua/nvim-lsp-installer/installers/init.lua
@@ -3,9 +3,9 @@ local Data = require "nvim-lsp-installer.data"
 
 local M = {}
 
-function M.join(installers)
+function M.pipe(installers)
     if #installers == 0 then
-        error "No installers to join."
+        error "No installers to pipe."
     end
 
     return function(server, callback, context)
@@ -30,27 +30,49 @@ end
 
 -- much fp, very wow
 function M.compose(installers)
-    return M.join(Data.list_reverse(installers))
+    return M.pipe(Data.list_reverse(installers))
 end
 
+function M.always_succeed(installer)
+    return function(server, callback, context)
+        installer(server, function()
+            callback(true)
+        end, context)
+    end
+end
+
+local function get_by_platform(platform_table)
+    if platform.is_unix then
+        return platform_table.unix
+    elseif platform.is_win then
+        return platform_table.win
+    else
+        return nil
+    end
+end
+
+-- non-exhaustive
+function M.on(platform_table)
+    return function(server, callback, context)
+        local installer = get_by_platform(platform_table)
+        if installer then
+            installer(server, callback, context)
+        else
+            callback(true)
+        end
+    end
+end
+
+-- exhaustive
 function M.when(platform_table)
     return function(server, callback, context)
-        if platform.is_unix then
-            if platform_table.unix then
-                platform_table.unix(server, callback, context)
-            else
-                context.stdio_sink.stderr(("Unix is not yet supported for server %q."):format(server.name))
-                callback(false)
-            end
-        elseif platform.is_win then
-            if platform_table.win then
-                platform_table.win(server, callback, context)
-            else
-                context.stdio_sink.stderr(("Windows is not yet supported for server %q."):format(server.name))
-                callback(false)
-            end
+        local installer = get_by_platform(platform_table)
+        if installer then
+            installer(server, callback, context)
         else
-            context.sdtio_sink.stderr "installers.when: Could not find installer for current platform."
+            context.stdio_sink.stderr(
+                ("Current operating system is not yet supported for server %q."):format(server.name)
+            )
             callback(false)
         end
     end