Add Eio.Vars.t to Stdenv

lib_eio/process.ml

@@ -93,13 +93,15 @@ module Env = struct
     Printf.sprintf "%s=%s" name value
 
   let get_opt name t =
-    Name.validate name;
-    let prefix = name ^ "=" in
-    Array.find_opt (Name.starts_with ~prefix) t
-    |> Option.map (fun e ->
-        let i = String.length prefix in
-        String.sub e i (String.length e - i)
-      )
+    if name = "" then None
+    else (
+      let prefix = name ^ "=" in
+      Array.find_opt (Name.starts_with ~prefix) t
+      |> Option.map (fun e ->
+          let i = String.length prefix in
+          String.sub e i (String.length e - i)
+        )
+    )
 
   let override bindings t =
     List.iter validate_binding bindings;
@@ -163,6 +165,9 @@ module Pi = struct
     type tag
     type t
 
+    val environment : t -> Env.t
+    val getenv_opt : t -> string -> string option
+
     val pipe :
       t ->
       sw:Switch.t ->
@@ -221,6 +226,16 @@ let signal (type tag) (t : [> tag ty] r) s =
   let module X = (val (Resource.get ops Pi.Process)) in
   X.signal v s
 
+let environment (type tag) (t : [> tag mgr_ty] r) =
+  let (Resource.T (v, ops)) = t in
+  let module X = (val (Resource.get ops Pi.Mgr)) in
+  X.environment v
+
+let getenv_opt (type tag) (t : [> tag mgr_ty] r) =
+  let (Resource.T (v, ops)) = t in
+  let module X = (val (Resource.get ops Pi.Mgr)) in
+  X.getenv_opt v
+
 let spawn (type tag) ~sw (t : [> tag mgr_ty] r) ?cwd ?stdin ?stdout ?stderr ?env ?executable args : tag ty r =
   let (Resource.T (v, ops)) = t in
   let module X = (val (Resource.get ops Pi.Mgr)) in

lib_eio/process.mli

@@ -52,6 +52,8 @@ type 'a mgr = 'a r
  constraint 'a = [> [> `Generic] mgr_ty]
 (** A process manager capable of spawning new processes. *)
 
+(** {2 Environment variables} *)
+
 module Env : sig
   (** A list of environment variable entries.
 
@@ -79,9 +81,8 @@ module Env : sig
       This just adds [xs] to {!empty} using {!override}. *)
 
   val get_opt : string -> t -> string option
-  (** [get_opt name t] is the value of [name] in [t], or [None] if there is no such binding.
-
-      @raise Invalid_argument if [name] is not a valid name. *)
+  (** [get_opt name t] is the value of [name] in [t], or [None] if there is no such binding
+      (or if [name] is not a valid name). *)
 
   val override : (string * string option) list -> t -> t
   (** [override bindings t] is a new environment which is like [t]
@@ -109,6 +110,13 @@ module Env : sig
   val pp : t Fmt.t
 end
 
+val environment : _ mgr -> Env.t
+(** [environment t] returns a snapshot of this process's current environment. *)
+
+val getenv_opt : _ mgr -> string -> string option
+(** [getenv_opt t name] will get the environment variable called [name].
+    Returns [None] if [name] does not exist. *)
+
 (** {2 Processes} *)
 
 val pid : _ t -> int
@@ -228,6 +236,9 @@ module Pi : sig
     type tag
     type t
 
+    val environment : t -> Env.t
+    val getenv_opt : t -> string -> string option
+
     val pipe :
       t ->
       sw:Switch.t ->

lib_eio/unix/process.ml

@@ -136,6 +136,9 @@ end) = struct
 
   type tag = [ `Generic | `Unix ]
 
+  let environment _t = Unix.environment () |> Eio.Process.Env.of_array
+  let getenv_opt _t name = Sys.getenv_opt name
+
   let pipe _ ~sw =
     (Private.pipe sw :> ([Eio.Resource.close_ty | Eio.Flow.source_ty] r *
     [Eio.Resource.close_ty | Eio.Flow.sink_ty] r))

lib_eio_linux/tests/spawn.md

@@ -7,8 +7,6 @@ open Eio.Std
 
 module Env = Eio.Process.Env
 module Process = Eio_linux.Low_level.Process
-
-let default_env = Unix.environment () |> Env.of_array
 ```
 
 ## Spawning processes
@@ -31,7 +29,8 @@ FOO=bar
 Changing directory:
 
 ```ocaml
-# Eio_linux.run @@ fun _env ->
+# Eio_linux.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   let child = Process.spawn ~sw Process.Fork_action.[
     chdir "/";
@@ -47,7 +46,8 @@ Changing directory:
 Changing directory using a file descriptor:
 
 ```ocaml
-# Eio_linux.run @@ fun _env ->
+# Eio_linux.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   let root =
     Eio_linux.Low_level.openat2 ~sw "/"
@@ -71,7 +71,8 @@ Changing directory using a file descriptor:
 Exit status:
 
 ```ocaml
-# Eio_linux.run @@ fun _env ->
+# Eio_linux.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   let child = Process.spawn ~sw Process.Fork_action.[
     execve "/usr/bin/env"
@@ -85,7 +86,8 @@ Exit status:
 Failure starting child:
 
 ```ocaml
-# Eio_linux.run @@ fun _env ->
+# Eio_linux.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   Process.spawn ~sw Process.Fork_action.[
     chdir "/idontexist";
@@ -99,7 +101,8 @@ Exception: Unix.Unix_error(Unix.ENOENT, "chdir", "")
 Signalling a running child:
 
 ```ocaml
-# Eio_linux.run @@ fun _env ->
+# Eio_linux.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   let child =
     Process.spawn ~sw Process.Fork_action.[

lib_eio_posix/test/spawn.md

@@ -7,8 +7,6 @@ open Eio.Std
 
 module Env = Eio.Process.Env
 module Process = Eio_posix.Low_level.Process
-
-let default_env = Unix.environment () |> Env.of_array
 ```
 
 ## Spawning processes
@@ -31,7 +29,8 @@ FOO=bar
 Changing directory:
 
 ```ocaml
-# Eio_posix.run @@ fun _env ->
+# Eio_posix.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   let child = Process.spawn ~sw Process.Fork_action.[
     chdir "/";
@@ -47,7 +46,8 @@ Changing directory:
 Changing directory using a file descriptor:
 
 ```ocaml
-# Eio_posix.run @@ fun _env ->
+# Eio_posix.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   let root = Eio_posix.Low_level.openat ~sw ~mode:0 Fs "/" Eio_posix.Low_level.Open_flags.(rdonly + directory) in
   let child = Process.spawn ~sw Process.Fork_action.[
@@ -64,7 +64,8 @@ Changing directory using a file descriptor:
 Exit status:
 
 ```ocaml
-# Eio_posix.run @@ fun _env ->
+# Eio_posix.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   let child = Process.spawn ~sw Process.Fork_action.[
     execve "/usr/bin/env"
@@ -78,7 +79,8 @@ Exit status:
 Failure starting child:
 
 ```ocaml
-# Eio_posix.run @@ fun _env ->
+# Eio_posix.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   Process.spawn ~sw Process.Fork_action.[
     chdir "/idontexist";
@@ -92,7 +94,8 @@ Exception: Unix.Unix_error(Unix.ENOENT, "chdir", "")
 Signalling a running child:
 
 ```ocaml
-# Eio_posix.run @@ fun _env ->
+# Eio_posix.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   let child =
     Process.spawn ~sw Process.Fork_action.[
@@ -163,7 +166,8 @@ let read_all pipe =
 Swapping FDs (note: plain sh can't handle multi-digit FDs!):
 
 ```ocaml
-# Eio_posix.run @@ fun _env ->
+# Eio_posix.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   let pipe1_r, pipe1_w = Eio_unix.pipe sw in
   let pipe2_r, pipe2_w = Eio_unix.pipe sw in
@@ -208,7 +212,8 @@ Swapping FDs (note: plain sh can't handle multi-digit FDs!):
 Keeping an FD open:
 
 ```ocaml
-# Eio_posix.run @@ fun _env ->
+# Eio_posix.run @@ fun env ->
+  let default_env = Eio.Stdenv.process_mgr env |> Eio.Process.environment in
   Switch.run @@ fun sw ->
   let pipe1_r, pipe1_w = Eio_unix.pipe sw in
   let child =

tests/process.md

@@ -233,6 +233,16 @@ A custom environment:
 - : string = ":2"
 ```
 
+Using the parent's environment explicitly:
+
+```ocaml
+# run @@ fun mgr env ->
+  Unix.putenv "DISPLAY" ":1";
+  let env = Eio.Process.environment mgr in
+  Process.parse_out ~env mgr Eio.Buf_read.line ["sh"; "-c"; "echo $DISPLAY"];;
+- : string = ":1"
+```
+
 Eio's child reaping code doesn't interfere with OCaml's process spawning:
 
 ```ocaml
@@ -293,10 +303,8 @@ Invalid environment variable name "k="
 # e |> Env.override ["k", Some "v=1"] |> Env.get_opt "k";;
 - : string option = Some "v=1"
 
-# try Env.(get_opt "" empty) |> ignore
-  with Invalid_argument x -> print_endline x;;
-Invalid environment variable name ""
-- : unit = ()
+# Env.(get_opt "" (of_array [| "=foo" |]));;
+- : string option = None
 
 # try e |> Env.override ["", None] |> ignore
   with Invalid_argument x -> print_endline x;;
@@ -320,3 +328,26 @@ val e : Env.t = [""
              "c=5"
              "c=6"]
 ```
+
+Using the environment capability:
+
+```ocaml
+# run @@ fun mgr _env ->
+  Unix.putenv "DISPLAY" ":1";
+  Eio.Process.getenv_opt mgr "DISPLAY";;
+- : string option = Some ":1"
+```
+
+```ocaml
+# run @@ fun mgr _env ->
+  Eio.Process.getenv_opt mgr "THIS_VAR_PROBABLY_WILL_NOT_EXIST";;
+- : string option = None
+```
+
+```ocaml
+# run @@ fun mgr _env ->
+  Unix.putenv "DISPLAY" ":1";
+  let env = Eio.Process.environment mgr in
+  Eio.Process.Env.get_opt "DISPLAY" env;;
+- : string option = Some ":1"
+```