Handle binwrite failures in installer

Since Elixir 1.16, the IO.binwrite/2 function no longer returns an
:ok- or :error tuple. Instead, it simply raises an error when it
fails.

To keep compatibility with previous versions of Elixir, this patch
implements binwrite_with_result, which is a delegate of IO.binwrite/2
on versions before 1.16, and a try-catch wrapper for Elixir 1.16 and
above.

With that function in place, the precious implementation is restored,
which prints "Failure!" before the error message in the unlikely event
that the write fails.

Co-authored-by: Tom de Bruijn <[email protected]>

lib/mix/tasks/appsignal.install.ex

@@ -183,8 +183,15 @@ defmodule Mix.Tasks.Appsignal.Install do
 
     case File.open(appsignal_config_file_path(), [:write]) do
       {:ok, file} ->
-        IO.binwrite(file, appsignal_config_file_contents(config))
-        IO.puts("Success!")
+        case binwrite_with_result(file, appsignal_config_file_contents(config)) do
+          :ok ->
+            IO.puts("Success!")
+
+          {:error, reason} ->
+            IO.puts("Failure! #{inspect(reason)}")
+            exit(:shutdown)
+        end
+
         File.close(file)
 
       {:error, reason} ->
@@ -193,6 +200,18 @@ defmodule Mix.Tasks.Appsignal.Install do
     end
   end
 
+  if Version.match?(System.version(), ">= 1.16.0") do
+    defp binwrite_with_result(path, contents) do
+      try do
+        IO.binwrite(path, contents)
+      catch
+        {:error, reason} -> {:error, reason}
+      end
+    end
+  else
+    defdelegate binwrite_with_result(path, contents), to: IO, as: :binwrite
+  end
+
   # Link the config/appsignal.exs config file to the config/config.exs file.
   # If already linked, it's ignored.
   defp link_config_file do