Handle Unknown errors in Erlang

CHANGELOG.md

@@ -3,6 +3,8 @@
 - Add documentation for 'mode' field in FileInfo.
 
 ## Unreleased
+- Add support for POSIX error `Ehostdown`.
+- Fix bug where unknown errrs were not handled in Erlang ffi.
 
 ## v2.3.1 - 6 November 2025 
 - Fix bug with error string typo for `Enotdir` on JS.

src/simplifile.gleam

@@ -39,6 +39,8 @@ pub type FileError {
   /// Inappropriate file type or format. Usually caused by trying to set the
   /// "sticky bit" on a regular file (not a directory).
   Eftype
+  /// Host is down.
+  Ehostdown
   /// Interrupted system call.
   Eintr
   /// Invalid argument.
@@ -170,6 +172,7 @@ pub fn describe_error(error: FileError) -> String {
     Enosr -> "No STREAM resources"
     Enostr -> "Not a STREAM"
     Eopnotsupp -> "Operation not supported on socket"
+    Ehostdown -> "Host is down"
     NotUtf8 -> "File not UTF-8 encoded"
     Unknown(inner) -> "Unknown error: " <> inner
   }

src/simplifile_erl.erl

@@ -46,6 +46,7 @@
         orelse Error =:= efault
         orelse Error =:= efbig
         orelse Error =:= eftype
+        orelse Error =:= ehostdown
         orelse Error =:= eintr
         orelse Error =:= einval
         orelse Error =:= eio
@@ -91,9 +92,14 @@ posix_result(Result) ->
         {ok, Value} ->
             {ok, Value};
         {error, Reason} when ?is_posix_error(Reason) ->
-            {error, Reason}
+            {error, Reason};
+        {error, Reason} ->
+            {error, {unknown, error_reason_to_binary(Reason)}}
     end.
 
+error_reason_to_binary(Reason) ->
+	unicode:characters_to_binary(io_lib:format("~tp", [Reason])).
+
 %% Read the binary contents of a file
 read_bits(Filename) ->
     posix_result(file:read_file(Filename)).

src/simplifile_js.mjs

@@ -324,6 +324,8 @@ function cast_error(error_code) {
       return new $simplifile.Eftype();
     case "EINTR":
       return new $simplifile.Eintr();
+    case "EHOSTDOWN":
+      return new $simplifile.Ehostdown();
     case "EINVAL":
       return new $simplifile.Einval();
     case "EIO":

test/create_directory_bad_arg.mjs

@@ -0,0 +1,5 @@
+import { createDirectory } from "./simplifile_js.mjs";
+
+export function createDirectoryWithBadArg(arg) {
+	return createDirectory(arg);
+}

test/simplifile_test.gleam

@@ -1,18 +1,19 @@
 import gleam/int
 import gleam/list
 import gleam/set
+import gleam/string
 import gleeunit
 import gleeunit/should
-import simplifile.{
+import simplifile.{type FileError,
   Directory, Eacces, Eagain, Ebadf, Ebadmsg, Ebusy, Edeadlk, Edeadlock, Edquot,
-  Eexist, Efault, Efbig, Eftype, Einval, Eio, Eisdir, Eloop, Emfile, Emlink,
-  Emultihop, Enametoolong, Enfile, Enobufs, Enodev, Enoent, Enolck, Enolink,
-  Enomem, Enospc, Enosr, Enostr, Enosys, Enotblk, Enotdir, Enotsup, Enxio,
+  Eexist, Efault, Efbig, Eftype, Ehostdown, Einval, Eio, Eisdir, Eloop, Emfile,
+  Emlink, Emultihop, Enametoolong, Enfile, Enobufs, Enodev, Enoent, Enolck,
+  Enolink, Enomem, Enospc, Enosr, Enostr, Enosys, Enotblk, Enotdir, Enotsup, Enxio,
   Eopnotsupp, Eoverflow, Eperm, Epipe, Erange, Erofs, Espipe, Esrch, Estale,
-  Etxtbsy, Exdev, Execute, File, FilePermissions, NotUtf8, Read, Unknown, Write,
-  append, append_bits, copy, copy_directory, copy_file, create_directory,
-  create_directory_all, create_file, create_link, create_symlink, delete,
-  delete_all, file_info, file_info_permissions, file_info_permissions_octal,
+  Etxtbsy, Exdev, Execute, File, FilePermissions, NotUtf8, Read,
+  Unknown, Write, append, append_bits, copy, copy_directory, copy_file,
+  create_directory, create_directory_all, create_file, create_link, create_symlink,
+  delete, delete_all, file_info, file_info_permissions, file_info_permissions_octal,
   file_info_type, file_permissions_to_octal, get_files, is_directory, is_file,
   is_symlink, link_info, read, read_bits, read_directory, rename,
   set_permissions, set_permissions_octal, write, write_bits,
@@ -483,7 +484,11 @@ pub fn file_info_get_permissions_test() {
 pub fn get_files_with_slash_test() {
   let assert Ok(files) = get_files(in: "./test/")
   files
-  |> should.equal(["./test/simplifile_test.gleam"])
+  |> list.sort(string.compare)
+  |> should.equal([
+    "./test/create_directory_bad_arg.mjs",
+    "./test/simplifile_test.gleam",
+  ])
 }
 
 // This test is only for local development
@@ -692,6 +697,8 @@ pub fn describe_error_test() {
   let assert "Operation not supported on socket" =
     simplifile.describe_error(Eopnotsupp)
 
+  let assert "Host is down" = simplifile.describe_error(Ehostdown)
+
   let assert "File not UTF-8 encoded" = simplifile.describe_error(NotUtf8)
 
   let assert "Unknown error: Something went wrong" =
@@ -761,3 +768,17 @@ pub fn parse_errors_test() {
     simplifile.create_directory_all("./tmp/wumbo/wombo") |> should.be_error
   err |> should.equal(Enotdir)
 }
+
+pub fn unknown_errors_return_unknown_test() {
+	let err = create_directory_with_bad_arg(#(Nil, Nil))
+  err |> should.be_error
+
+  let assert Error(unknown) = err
+  let assert Unknown(inner) = unknown
+	inner |> should.not_equal("")
+}
+
+// This is necessary to force unknown error generation uniformly across runtimes
+@external(erlang, "simplifile_erl", "create_directory")
+@external(javascript, "./create_directory_bad_arg.mjs", "createDirectoryWithBadArg")
+fn create_directory_with_bad_arg(arg: #(Nil, Nil)) -> Result(Nil, FileError)