fix: correctly set MIX_HOME when using bundled Elixir

lib/next_ls.ex

@@ -89,8 +89,6 @@ defmodule NextLS do
     cache = Keyword.fetch!(args, :cache)
     {:ok, logger} = DynamicSupervisor.start_child(dynamic_supervisor, {NextLS.Logger, lsp: lsp})
 
-    NextLS.Runtime.BundledElixir.install(bundle_base, logger, mix_home: mix_home)
-
     {:ok,
      assign(lsp,
        auto_update: Keyword.get(args, :auto_update, false),
@@ -132,6 +130,13 @@ defmodule NextLS do
 
     {:ok, init_opts} = __MODULE__.InitOpts.validate(init_opts)
 
+    mix_home =
+      if init_opts.experimental.completions.enable do
+        NextLS.Runtime.BundledElixir.mix_home(lsp.assigns.bundle_base)
+      else
+        nil
+      end
+
     {:reply,
      %InitializeResult{
        capabilities: %ServerCapabilities{
@@ -175,6 +180,7 @@ defmodule NextLS do
        server_info: %{name: "Next LS"}
      },
      assign(lsp,
+       mix_home: mix_home,
        root_uri: root_uri,
        workspace_folders: workspace_folders,
        client_capabilities: caps,
@@ -868,6 +874,7 @@ defmodule NextLS do
         })
     end
 
+    NextLS.Runtime.BundledElixir.install(lsp.assigns.bundle_base, lsp.assigns.logger)
     GenLSP.log(lsp, "[Next LS] Booting runtimes...")
 
     parent = self()

lib/next_ls/runtime.ex

@@ -140,19 +140,24 @@ defmodule NextLS.Runtime do
         |> Path.join("cmd")
         |> Path.absname()
 
-      env = [
-        {~c"LSP", ~c"nextls"},
-        {~c"NEXTLS_PARENT_PID", parent},
-        {~c"MIX_ENV", ~c"#{mix_env}"},
-        {~c"MIX_TARGET", ~c"#{mix_target}"},
-        {~c"MIX_BUILD_ROOT", ~c".elixir-tools/_build"},
-        {~c"MIX_HOME", ~c"#{mix_home}"},
-        {~c"ROOTDIR", false},
-        {~c"BINDIR", false},
-        {~c"RELEASE_ROOT", false},
-        {~c"RELEASE_SYS_CONFIG", false},
-        {~c"PATH", String.to_charlist(new_path)}
-      ]
+      env =
+        [
+          {~c"LSP", ~c"nextls"},
+          {~c"NEXTLS_PARENT_PID", parent},
+          {~c"MIX_ENV", ~c"#{mix_env}"},
+          {~c"MIX_TARGET", ~c"#{mix_target}"},
+          {~c"MIX_BUILD_ROOT", ~c".elixir-tools/_build"},
+          {~c"ROOTDIR", false},
+          {~c"BINDIR", false},
+          {~c"RELEASE_ROOT", false},
+          {~c"RELEASE_SYS_CONFIG", false},
+          {~c"PATH", String.to_charlist(new_path)}
+        ] ++
+          if mix_home do
+            [{~c"MIX_HOME", ~c"#{mix_home}"}]
+          else
+            []
+          end
 
       args =
         [elixir_exe] ++

lib/next_ls/runtime/bundled_elixir.ex

@@ -20,9 +20,13 @@ defmodule NextLS.Runtime.BundledElixir do
     Path.join([base, @dir])
   end
 
-  def install(base, logger, opts \\ []) do
-    basedir = path(base)
-    mixhome = Keyword.get(opts, :mix_home) || Path.join(basedir, ".mix")
+  def mix_home(base) do
+    Path.join(path(base), ".mix")
+  end
+
+  def install(base, logger) do
+    mixhome = mix_home(base)
+    File.mkdir_p!(mixhome)
     binpath = binpath(base)
 
     unless File.exists?(binpath) do
@@ -37,16 +41,16 @@ defmodule NextLS.Runtime.BundledElixir do
       for bin <- Path.wildcard(Path.join(binpath, "*")) do
         File.chmod(bin, 0o755)
       end
+    end
 
-      new_path = "#{binpath}:#{System.get_env("PATH")}"
-      mixbin = mixpath(base)
+    new_path = "#{binpath}:#{System.get_env("PATH")}"
+    mixbin = mixpath(base)
 
-      {_, 0} =
-        System.cmd(mixbin, ["local.rebar", "--force"], env: [{"PATH", new_path}, {"MIX_HOME", mixhome}])
+    {_, 0} =
+      System.cmd(mixbin, ["local.rebar", "--force"], env: [{"PATH", new_path}, {"MIX_HOME", mixhome}])
 
-      {_, 0} =
-        System.cmd(mixbin, ["local.hex", "--force"], env: [{"PATH", new_path}, {"MIX_HOME", mixhome}])
-    end
+    {_, 0} =
+      System.cmd(mixbin, ["local.hex", "--force"], env: [{"PATH", new_path}, {"MIX_HOME", mixhome}])
 
     :ok
   rescue