From cfc21c6402cef79ccb9765e2c88ea0a9c4552616 Mon Sep 17 00:00:00 2001
From: m <m@sirabella.org>
Date: Tue, 23 Sep 2025 12:49:13 -0700
Subject: [PATCH 1/6] Err on receive() on other-owned named process & forever

---
 src/gleam/erlang/process.gleam       | 26 +++++++++++++++++---------
 test/gleam/erlang/process_test.gleam | 20 ++++++++++++++++++++
 2 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/src/gleam/erlang/process.gleam b/src/gleam/erlang/process.gleam
index 7172233..dd85488 100644
--- a/src/gleam/erlang/process.gleam
+++ b/src/gleam/erlang/process.gleam
@@ -243,14 +243,11 @@ pub fn receive(
   from subject: Subject(message),
   within timeout: Int,
 ) -> Result(message, Nil) {
-  case subject {
-    NamedSubject(..) -> perform_receive(subject, timeout)
-    Subject(owner:, ..) ->
-      case owner == self() {
-        True -> perform_receive(subject, timeout)
-        False ->
-          panic as "Cannot receive with a subject owned by another process"
-      }
+  let self = self()
+  case subject_owner(subject) {
+    Ok(pid) if pid == self -> perform_receive(subject, timeout)
+    _ ->
+      panic as "Cannot receive with a subject owned by another process"
   }
 }
 
@@ -263,8 +260,19 @@ fn perform_receive(
 /// Receive a message that has been sent to current process using the `Subject`.
 ///
 /// Same as `receive` but waits forever and returns the message as is.
+pub fn receive_forever(from subject: Subject(message)) -> message {
+  let self = self()
+  case subject_owner(subject) {
+    Ok(pid) if pid == self -> perform_receive_forever(subject)
+    _ ->
+      panic as "Cannot receive with a subject owned by another process"
+  }
+}
+
 @external(erlang, "gleam_erlang_ffi", "receive")
-pub fn receive_forever(from subject: Subject(message)) -> message
+fn perform_receive_forever(from subject: Subject(message)) -> message
+
+
 
 /// A type that enables a process to wait for messages from multiple `Subject`s
 /// at the same time, returning whichever message arrives first.
diff --git a/test/gleam/erlang/process_test.gleam b/test/gleam/erlang/process_test.gleam
index 1a86c2b..c418855 100644
--- a/test/gleam/erlang/process_test.gleam
+++ b/test/gleam/erlang/process_test.gleam
@@ -112,6 +112,15 @@ pub fn receive_forever_test() {
   let assert 2 = process.receive_forever(subject)
 }
 
+pub fn receive_forever_other_test() {
+  let subject = process.new_subject()
+  process.spawn(fn() { process.send(subject, process.new_subject()) })
+  let subject = process.receive_forever(subject)
+
+  assert assert_panic(fn() { process.receive_forever(subject) })
+    == "Cannot receive with a subject owned by another process"
+}
+
 pub fn is_alive_test() {
   let pid = process.spawn_unlinked(fn() { Nil })
   process.sleep(5)
@@ -666,3 +675,14 @@ pub fn name_test() {
   let assert Ok("Hello") = process.receive(subject, 0)
   process.unregister(name)
 }
+
+pub fn name_other_test() {
+  let name = process.new_name("name")
+  let pid = process.spawn_unlinked(fn() { process.sleep(10) })
+  let assert Ok(_) = process.register(pid, name)
+  let subject = process.named_subject(name)
+  process.send(subject, "Hello")
+  assert assert_panic(fn() { process.receive(subject, 5) })
+    == "Cannot receive with a subject owned by another process"
+  process.unregister(name)
+}

From 0d66f8e40701a6593b3f50c177a9701be3cd6c94 Mon Sep 17 00:00:00 2001
From: m <m@sirabella.org>
Date: Tue, 23 Sep 2025 14:05:05 -0700
Subject: [PATCH 2/6] Add even more tests surrounding named send/receive

---
 test/gleam/erlang/process_test.gleam | 53 ++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/test/gleam/erlang/process_test.gleam b/test/gleam/erlang/process_test.gleam
index c418855..4faab9c 100644
--- a/test/gleam/erlang/process_test.gleam
+++ b/test/gleam/erlang/process_test.gleam
@@ -686,3 +686,56 @@ pub fn name_other_test() {
     == "Cannot receive with a subject owned by another process"
   process.unregister(name)
 }
+
+
+// tests that sending/receiving on names fail if the name gets unregistered
+pub fn unregister_receive_test() {
+  let name = process.new_name("name")
+  let assert Ok(_) = process.register(process.self(), name)
+  let subject = process.named_subject(name)
+
+  process.send(subject, "Hello")
+  let assert Ok("Hello") = process.receive(subject, 0)
+
+  let assert Ok(_) = process.unregister(name)
+
+  assert assert_panic(fn() { process.send(subject, "Hello") })
+    == "Sending to unregistered name"
+  assert assert_panic(fn() { process.receive(subject, 0) })
+    == "Cannot receive with a subject owned by another process" // this error message could be better
+}
+
+// tests that receiving on names fail if the registration gets moved during execution
+pub fn name_other_switchover_test() {
+  let name = process.new_name("name")
+  let self = process.self()
+  let assert Ok(_) = process.register(self, name)
+  let subject = process.named_subject(name)
+
+  assert Ok(self) == process.subject_owner(subject)
+
+  process.send(subject, "Hello")
+  let assert Ok("Hello") = process.receive(subject, 0)
+
+  let pid = process.spawn(fn() {
+    process.sleep(10)
+    let assert Ok(_) = process.unregister(name) // "undesirable behaviour"
+    let assert Ok(_) = process.register(process.self(), name)
+
+    process.sleep(20)
+    let assert Ok("Peace") = process.receive(subject, 0)
+  })
+
+  assert Ok(self) == process.subject_owner(subject)
+
+  process.send(subject, "World")
+  let assert Ok("World") = process.receive(subject, 0)
+
+  assert Ok(self) == process.subject_owner(subject)
+  process.sleep(12)
+  assert Ok(pid) == process.subject_owner(subject)
+
+  process.send(subject, "Peace")
+  assert assert_panic(fn() { process.receive(subject, 0) })
+    == "Cannot receive with a subject owned by another process"
+}

From 3d1d8f4ca8cc126cdbdf1274e5c9a36021039677 Mon Sep 17 00:00:00 2001
From: m <m@sirabella.org>
Date: Mon, 22 Sep 2025 16:53:10 -0700
Subject: [PATCH 3/6] Add MVP port stuff

Fixes #89

port and process are still inextricably coupled, most of the complex
things I would want to do already require process' recieve/subject
tooling.

the recursive dependencies are really a bitch too, I would much rather
prefer `port` module define a lot of this stuff

This integrates a lot of the port stuff into process.gleam since
representing a port-based subject as PortSubject lets us do two things:

- Disallow send() on PortSubjects with a panic
- check subject_owner at runtime that the port subject is still the
  calling process
---
 src/gleam/erlang/port.gleam         | 72 +++++++++++++++++++++++++++++
 src/gleam/erlang/port/receive.gleam |  5 ++
 src/gleam/erlang/process.gleam      | 43 ++++++++++++++++-
 src/gleam_erlang_ffi.erl            | 38 ++++++++++++++-
 test/gleam/erlang/port_test.gleam   | 63 +++++++++++++++++++++++++
 5 files changed, 219 insertions(+), 2 deletions(-)
 create mode 100644 src/gleam/erlang/port/receive.gleam
 create mode 100644 test/gleam/erlang/port_test.gleam

diff --git a/src/gleam/erlang/port.gleam b/src/gleam/erlang/port.gleam
index 4e1b4d8..cf04b35 100644
--- a/src/gleam/erlang/port.gleam
+++ b/src/gleam/erlang/port.gleam
@@ -1,3 +1,5 @@
+import gleam/dynamic
+
 /// Ports are how code running on the Erlang virtual machine interacts with
 /// the outside world. Bytes of data can be sent to and read from ports,
 /// providing a form of message passing to an external program or resource.
@@ -7,3 +9,73 @@
 /// [1]: https://erlang.org/doc/reference_manual/ports.html
 ///
 pub type Port
+
+pub type PortCommand {
+  Spawn(String)
+  SpawnDriver(String)
+  SpawnExecutable(String)
+  Fd(in: Int, out: Int)
+}
+
+pub fn spawn(command: String) -> PortCommand {
+  Spawn(command)
+}
+
+pub fn spawn_driver(command: String) -> PortCommand {
+  SpawnDriver(command)
+}
+
+pub fn spawn_executable(command: String) -> PortCommand {
+  SpawnExecutable(command)
+}
+
+
+pub type PortOptions {
+  Arg0(String)
+  Args(List(String))
+  Env(List(#(String, String)))
+  Cd(String)
+  Binary
+
+  UseStdio
+  NouseStdio
+
+  Eof
+  ExitStatus
+
+  Stream
+  Line(Int)
+  Packet(Int) // only 1, 2, & 4
+}
+
+pub type PortError {
+  Badarg
+  SystemLimit
+  Enomem
+  Eagain
+  Enametoolong
+  Emfile
+  Enfile
+  Eaccess
+  Enoent
+}
+
+@external(erlang, "gleam_erlang_ffi", "my_open_port")
+pub fn open(
+  name: PortCommand,
+  settings: List(PortOptions),
+) -> Result(Port, PortError)
+
+@external(erlang, "erlang", "port_command")
+pub fn port_command(
+  port: Port,
+  data: BitArray,
+  options: List(PortOptions),
+) -> Nil
+
+
+@external(erlang, "gleam_erlang_ffi", "identity")
+pub fn to_dynamic(a: Port) -> dynamic.Dynamic
+
+@external(erlang, "erlang", "port_close")
+pub fn close(port: Port) -> Nil
diff --git a/src/gleam/erlang/port/receive.gleam b/src/gleam/erlang/port/receive.gleam
new file mode 100644
index 0000000..2df8420
--- /dev/null
+++ b/src/gleam/erlang/port/receive.gleam
@@ -0,0 +1,5 @@
+pub type PortData {
+  Data(BitArray)
+  ExitStatus(Int)
+  Eof
+}
diff --git a/src/gleam/erlang/process.gleam b/src/gleam/erlang/process.gleam
index dd85488..21560d3 100644
--- a/src/gleam/erlang/process.gleam
+++ b/src/gleam/erlang/process.gleam
@@ -2,7 +2,9 @@ import gleam/dynamic.{type Dynamic}
 import gleam/dynamic/decode
 import gleam/erlang/atom.{type Atom}
 import gleam/erlang/port.{type Port}
+import gleam/erlang/port/receive.{type PortData}
 import gleam/erlang/reference.{type Reference}
+import gleam/result
 import gleam/string
 
 /// A `Pid` (or Process identifier) is a reference to an Erlang process. Each
@@ -78,6 +80,8 @@ pub fn spawn_unlinked(a: fn() -> anything) -> Pid
 pub opaque type Subject(message) {
   Subject(owner: Pid, tag: Dynamic)
   NamedSubject(name: Name(message))
+  // backup_owner needs to exist because ports close and we can't deduce the owner after a port closes, but the messages still exist in a mailbox of a pid
+  PortSubject(port: Port, backup_owner: Pid)
 }
 
 /// Create a subject for the given process with the give tag. This is unsafe!
@@ -149,7 +153,7 @@ pub fn named_subject(name: Name(message)) -> Subject(message) {
 pub fn subject_name(subject: Subject(message)) -> Result(Name(message), Nil) {
   case subject {
     NamedSubject(name:) -> Ok(name)
-    Subject(..) -> Error(Nil)
+    _ -> Error(Nil)
   }
 }
 
@@ -159,6 +163,31 @@ pub fn new_subject() -> Subject(message) {
   Subject(owner: self(), tag: reference_to_dynamic(reference.new()))
 }
 
+
+pub fn port_subject(port: Port) -> Subject(PortData) {
+  PortSubject(
+    port: port,
+    backup_owner: port_owner(port) |> result.unwrap(self()),
+  )
+}
+
+pub fn port_open(command: port.PortCommand, options: List(port.PortOptions)) -> Result(Subject(PortData), _) {
+  port.open(command, options) |> result.map(port_subject)
+}
+
+@external(erlang, "erlang", "port_connect")
+fn perform_port_connect(port: Port, pid: Pid) -> Nil
+
+pub fn port_connect(port: Port, pid: Pid) -> Subject(PortData) {
+  perform_port_connect(port, pid)
+  PortSubject(port, backup_owner: pid)
+}
+
+/// Returns Error if the port is already closed
+/// if possible, try to use subject_owner()
+@external(erlang, "gleam_erlang_ffi", "port_owner")
+pub fn port_owner(port: Port) -> Result(Pid, Nil)
+
 /// Get the owner process for a subject, which is the process that will
 /// receive any messages sent using the subject.
 ///
@@ -169,6 +198,14 @@ pub fn subject_owner(subject: Subject(message)) -> Result(Pid, Nil) {
   case subject {
     NamedSubject(name) -> named(name)
     Subject(pid, _) -> Ok(pid)
+    PortSubject(port, backup_owner) -> Ok(port_owner(port) |> result.unwrap(backup_owner))
+  }
+}
+
+pub fn subject_port(subject: Subject(message)) -> Result(Port, Nil) {
+  case subject {
+    PortSubject(port, ..) -> Ok(port)
+    _ -> Error(Nil)
   }
 }
 
@@ -215,6 +252,7 @@ pub fn send(subject: Subject(message), message: message) -> Nil {
       let assert Ok(pid) = named(name) as "Sending to unregistered name"
       raw_send(pid, #(name, message))
     }
+    PortSubject(..) -> panic as "Cannot send on PortSubject"
   }
   Nil
 }
@@ -420,6 +458,7 @@ pub fn select_map(
   case subject {
     NamedSubject(name) -> insert_selector_handler(selector, #(name, 2), handler)
     Subject(_, tag:) -> insert_selector_handler(selector, #(tag, 2), handler)
+    PortSubject(port:, ..) -> insert_selector_handler(selector, #(port, 2), handler)
   }
 }
 
@@ -433,6 +472,7 @@ pub fn deselect(
   case subject {
     NamedSubject(name) -> remove_selector_handler(selector, #(name, 2))
     Subject(_, tag:) -> remove_selector_handler(selector, #(tag, 2))
+    PortSubject(port:, ..) -> remove_selector_handler(selector, #(port, 2))
   }
 }
 
@@ -755,6 +795,7 @@ pub fn send_after(subject: Subject(msg), delay: Int, message: msg) -> Timer {
   case subject {
     NamedSubject(name) -> name_send_after(delay, name, #(name, message))
     Subject(owner, tag) -> pid_send_after(delay, owner, #(tag, message))
+    PortSubject(..) ->  panic as "Cannot send on PortSubject"
   }
 }
 
diff --git a/src/gleam_erlang_ffi.erl b/src/gleam_erlang_ffi.erl
index b1ad710..c331f17 100644
--- a/src/gleam_erlang_ffi.erl
+++ b/src/gleam_erlang_ffi.erl
@@ -5,7 +5,7 @@
     select/2, trap_exits/1, map_selector/2, merge_selector/2, flush_messages/0,
     priv_directory/1, connect_node/1, register_process/2, unregister_process/1,
     process_named/1, identity/1, 'receive'/1, 'receive'/2, new_name/1,
-    cast_down_message/1, cast_exit_reason/1
+    cast_down_message/1, cast_exit_reason/1, my_open_port/2, port_owner/1
 ]).
 
 -spec atom_from_string(binary()) -> {ok, atom()} | {error, nil}.
@@ -83,6 +83,10 @@ cast_down_message({'DOWN', Ref, port, Pid, Reason}) ->
     receive
         {Ref, Message} -> Message
     end;
+'receive'({port_subject, Port, _Pid}) ->
+    receive
+        {Port, Message} -> Message
+    end;
 'receive'({named_subject, Name}) ->
     receive
         {Name, Message} -> Message
@@ -94,6 +98,12 @@ cast_down_message({'DOWN', Ref, port, Pid, Reason}) ->
     after Timeout ->
         {error, nil}
     end;
+'receive'({port_subject, Port, _Pid}, Timeout) ->
+    receive
+        {Port, Message} -> {ok, Message}
+    after Timeout ->
+        {error, nil}
+    end;
 'receive'({named_subject, Name}, Timeout) ->
     receive
         {Name, Message} -> {ok, Message}
@@ -101,6 +111,32 @@ cast_down_message({'DOWN', Ref, port, Pid, Reason}) ->
         {error, nil}
     end.
 
+% sometimes this errors out if the port is already closed
+port_owner(Port) ->
+    case erlang:port_info(Port, connected) of
+        {connected, Pid} -> {ok, Pid};
+        undefined -> {error, nil}
+    end.
+
+my_open_port(PortName, PortSettings) ->
+    try
+        Port = open_port(PortName, PortSettings),
+        {ok, Port}
+    catch error:Reason ->
+        case Reason of
+            badarg -> {error, badarg};
+            system_limit -> {error, system_limit};
+            enomem -> {error, enomem};
+            eagain -> {error, eagain};
+            enametoolong -> {error, enametoolong};
+            emfile -> {error, emfile};
+            enfile -> {error, enfile};
+            eaccess -> {error, eaccess};
+            enoent -> {error, enoent}
+        end
+    end.
+
+
 demonitor(Reference) ->
     erlang:demonitor(Reference, [flush]).
 
diff --git a/test/gleam/erlang/port_test.gleam b/test/gleam/erlang/port_test.gleam
new file mode 100644
index 0000000..28f9460
--- /dev/null
+++ b/test/gleam/erlang/port_test.gleam
@@ -0,0 +1,63 @@
+import gleam/erlang/port
+import gleam/erlang/port/receive.{Data, ExitStatus}
+import gleam/erlang/process.{receive, port_open, port_subject}
+
+pub fn port_open_test() {
+  let assert Ok(port) = port.open(
+    port.spawn_executable("/bin/bash"),
+    [port.Args(["-c", "echo hi | wc -c"]), port.UseStdio, port.ExitStatus, port.Binary]
+  )
+
+  let subject = port_subject(port)
+
+  assert Ok(Data(<<"3\n">>)) == receive(subject, 100)
+  assert Ok(ExitStatus(0)) == receive(subject, 100)
+  assert Error(Nil) == receive(subject, 100)
+}
+
+pub fn fail_port_open_test() {
+  let assert Error(port.Enoent) = port.open(
+    port.spawn_executable("/bin/doesntexist"),
+    []
+  )
+}
+
+pub fn port_subject_test() {
+  let assert Ok(subject) = port_open(
+    port.spawn_executable("/bin/bash"),
+    [port.Args(["-c", "echo hello | wc -c"]), port.UseStdio, port.ExitStatus, port.Binary]
+  )
+
+  assert Ok(Data(<<"6\n">>)) == receive(subject, 100)
+  assert Ok(ExitStatus(0)) == receive(subject, 100)
+  assert Error(Nil) == receive(subject, 100)
+}
+
+pub fn close_port_test() {
+  let assert Ok(port) = port.open(
+    port.spawn_executable("/bin/bash"),
+    [port.Args(["-c", "echo hi; sleep 0.25; echo yo 2> /dev/null"]), port.UseStdio, port.ExitStatus, port.Binary]
+  )
+
+  let subject = port_subject(port)
+
+  assert Ok(Data(<<"hi\n">>)) == receive(subject, 100)
+
+  port.close(port)
+
+  assert Error(Nil) == receive(subject, 300)
+}
+
+pub fn delay_port_test() {
+  let assert Ok(port) = port.open(
+    port.spawn_executable("/bin/bash"),
+    [port.Args(["-c", "echo hi; sleep 0.25; echo yo 2> /dev/null"]), port.UseStdio, port.ExitStatus, port.Binary]
+  )
+
+  let subject = port_subject(port)
+  assert Ok(Data(<<"hi\n">>)) == receive(subject, 50)
+  assert Error(Nil) == receive(subject, 100)
+  assert Ok(Data(<<"yo\n">>)) == receive(subject, 300)
+  assert Ok(ExitStatus(0)) == receive(subject, 100)
+  assert Error(Nil) == receive(subject, 100)
+}

From 692529972253bc2d9dcc5c1e4542aa566ae74260 Mon Sep 17 00:00:00 2001
From: m <m@sirabella.org>
Date: Tue, 23 Sep 2025 14:33:04 -0700
Subject: [PATCH 4/6] Add a test for port ownership switchover

---
 test/gleam/erlang/port_test.gleam | 43 ++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/test/gleam/erlang/port_test.gleam b/test/gleam/erlang/port_test.gleam
index 28f9460..f8cc6d5 100644
--- a/test/gleam/erlang/port_test.gleam
+++ b/test/gleam/erlang/port_test.gleam
@@ -1,6 +1,9 @@
 import gleam/erlang/port
 import gleam/erlang/port/receive.{Data, ExitStatus}
-import gleam/erlang/process.{receive, port_open, port_subject}
+import gleam/erlang/process.{receive, port_open, port_connect, port_subject}
+
+@external(erlang, "gleam_erlang_test_ffi", "assert_gleam_panic")
+fn assert_panic(f: fn() -> t) -> String
 
 pub fn port_open_test() {
   let assert Ok(port) = port.open(
@@ -61,3 +64,41 @@ pub fn delay_port_test() {
   assert Ok(ExitStatus(0)) == receive(subject, 100)
   assert Error(Nil) == receive(subject, 100)
 }
+
+// mirrors name_other_switchover_test in process_test a bit
+pub fn port_switchover_test() {
+  // create a new port
+  let assert Ok(port) = port.open(
+    port.spawn_executable("/bin/bash"),
+    [port.Args(["-c", "cat"]), port.UseStdio, port.ExitStatus, port.Binary]
+  )
+
+  let subject = process.port_subject(port)
+
+  // verify we can listen on it
+  port.port_command(port, <<"wasd\n">>, [])
+  assert Ok(Data(<<"wasd\n">>)) == receive(subject, 5)
+
+  // switch the owner to some other erlang process
+  let pid = process.spawn(fn() { process.sleep(20) })
+  let newsubject = port_connect(port, pid)
+
+  // try to listen on it again
+  port.port_command(port, <<"test2\n">>, [])
+  assert assert_panic(fn() { process.receive(newsubject, 0) })
+    == "Cannot receive with a subject owned by another process"
+  // test the original subject, too
+  assert assert_panic(fn() { process.receive(subject, 0) })
+    == "Cannot receive with a subject owned by another process"
+
+  // let's switch back now
+  let newnewsubject = port_connect(port, process.self())
+  port.port_command(port, <<"test3\n">>, [])
+  assert Ok(Data(<<"test3\n">>)) == receive(subject, 5)
+  port.port_command(port, <<"test4\n">>, [])
+  assert Ok(Data(<<"test4\n">>)) == receive(newsubject, 5)
+  port.port_command(port, <<"test5\n">>, [])
+  assert Ok(Data(<<"test5\n">>)) == receive(newnewsubject, 5)
+
+  port.close(port)
+}

From cb0a12077d0023b9edf23f09cebc1d1672eb2fcc Mon Sep 17 00:00:00 2001
From: m <m@sirabella.org>
Date: Tue, 23 Sep 2025 15:09:13 -0700
Subject: [PATCH 5/6] Add test for verifying send isn't valid on port

---
 test/gleam/erlang/port_test.gleam | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/test/gleam/erlang/port_test.gleam b/test/gleam/erlang/port_test.gleam
index f8cc6d5..77cf2be 100644
--- a/test/gleam/erlang/port_test.gleam
+++ b/test/gleam/erlang/port_test.gleam
@@ -102,3 +102,19 @@ pub fn port_switchover_test() {
 
   port.close(port)
 }
+
+
+pub fn port_subject_send_test() {
+  let assert Ok(port) = port.open(
+    port.spawn_executable("/bin/bash"),
+    [port.Args(["-c", "cat"]), port.UseStdio, port.ExitStatus, port.Binary]
+  )
+
+  let subject = port_subject(port)
+
+
+  assert assert_panic(fn() { process.send(subject, Data(<<"hello">>)) })
+    == "Cannot send on PortSubject"
+
+  port.close(port)
+}

From f38a490cf5295b71dfeeb744632f06fb43354f3d Mon Sep 17 00:00:00 2001
From: m <m@sirabella.org>
Date: Tue, 23 Sep 2025 18:27:40 -0700
Subject: [PATCH 6/6] env takes charlist

---
 src/gleam/erlang/port.gleam       |  3 ++-
 test/gleam/erlang/port_test.gleam | 16 ++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/gleam/erlang/port.gleam b/src/gleam/erlang/port.gleam
index cf04b35..ba7f36c 100644
--- a/src/gleam/erlang/port.gleam
+++ b/src/gleam/erlang/port.gleam
@@ -1,4 +1,5 @@
 import gleam/dynamic
+import gleam/erlang/charlist.{type Charlist}
 
 /// Ports are how code running on the Erlang virtual machine interacts with
 /// the outside world. Bytes of data can be sent to and read from ports,
@@ -33,7 +34,7 @@ pub fn spawn_executable(command: String) -> PortCommand {
 pub type PortOptions {
   Arg0(String)
   Args(List(String))
-  Env(List(#(String, String)))
+  Env(List(#(Charlist, Charlist)))
   Cd(String)
   Binary
 
diff --git a/test/gleam/erlang/port_test.gleam b/test/gleam/erlang/port_test.gleam
index 77cf2be..a8fa113 100644
--- a/test/gleam/erlang/port_test.gleam
+++ b/test/gleam/erlang/port_test.gleam
@@ -1,6 +1,7 @@
 import gleam/erlang/port
 import gleam/erlang/port/receive.{Data, ExitStatus}
 import gleam/erlang/process.{receive, port_open, port_connect, port_subject}
+import gleam/erlang/charlist
 
 @external(erlang, "gleam_erlang_test_ffi", "assert_gleam_panic")
 fn assert_panic(f: fn() -> t) -> String
@@ -18,6 +19,21 @@ pub fn port_open_test() {
   assert Error(Nil) == receive(subject, 100)
 }
 
+pub fn port_env_open_test() {
+  let assert Ok(port) = port.open(
+    port.spawn_executable("/bin/bash"),
+    [
+      port.Args(["-c", "echo $VAR"]),
+      port.Env([#(charlist.from_string("VAR"), charlist.from_string("test123"))]),
+      port.UseStdio, port.ExitStatus, port.Binary
+    ]
+  )
+
+  let subject = port_subject(port)
+
+  assert Ok(Data(<<"test123\n">>)) == receive(subject, 100)
+}
+
 pub fn fail_port_open_test() {
   let assert Error(port.Enoent) = port.open(
     port.spawn_executable("/bin/doesntexist"),