feature: share os family of vars with rules

doc/changes/11863.md

@@ -0,0 +1,4 @@
+- Introduce `%{os}`,`%{os_version}`, `%{os_distribution}`, and `%{os_family}`
+  percent forms. These have the same values as their opam counterparts.
+  (#11863, @rgrinberg)
+

src/dune_lang/pform.ml

@@ -2,6 +2,25 @@ open Import
 module Payload = Template.Pform.Payload
 
 module Var = struct
+  module Os = struct
+    type t =
+      | Os
+      | Os_version
+      | Os_distribution
+      | Os_family
+
+    let all = [ Os; Os_version; Os_distribution; Os_family ]
+
+    let to_string = function
+      | Os -> "os"
+      | Os_version -> "os_version"
+      | Os_distribution -> "os_distribution"
+      | Os_family -> "os_family"
+    ;;
+
+    let to_dyn t = Dyn.variant (to_string t) []
+  end
+
   module Pkg = struct
     module Section = struct
       type t =
@@ -42,10 +61,7 @@ module Var = struct
 
     type t =
       | Switch
-      | Os
-      | Os_version
-      | Os_distribution
-      | Os_family
+      | Os of Os.t
       | Build
       | Prefix
       | User
@@ -58,11 +74,8 @@ module Var = struct
     let compare = Poly.compare
 
     let encode_to_latest_dune_lang_version = function
+      | Os s -> Os.to_string s
       | Switch -> "switch"
-      | Os -> "os"
-      | Os_version -> "os_version"
-      | Os_distribution -> "os_distribution"
-      | Os_family -> "os_family"
       | Build -> "build"
       | Prefix -> "prefix"
       | User -> "user"
@@ -107,6 +120,7 @@ module Var = struct
     | Profile
     | Context_name
     | Os_type
+    | Os of Os.t
     | Architecture
     | Arch_sixtyfour
     | System
@@ -174,6 +188,7 @@ module Var = struct
        | Corrected_suffix -> variant "Corrected_suffix" []
        | Inline_tests -> variant "Inline_tests" []
        | Toolchain -> variant "Toolchain" []
+       | Os os -> Os.to_dyn os
        | Pkg pkg -> Pkg.to_dyn pkg)
   ;;
 
@@ -184,10 +199,10 @@ module Var = struct
       (match name with
        | "make" -> Some Make
        | "switch" -> Some (Pkg Switch)
-       | "os" -> Some (Pkg Os)
-       | "os-version" -> Some (Pkg Os_version)
-       | "os-distribution" -> Some (Pkg Os_distribution)
-       | "os-family" -> Some (Pkg Os_family)
+       | "os" -> Some (Pkg (Os Os))
+       | "os-version" -> Some (Pkg (Os Os_version))
+       | "os-distribution" -> Some (Pkg (Os Os_distribution))
+       | "os-family" -> Some (Pkg (Os Os_family))
        | "build" -> Some (Pkg Build)
        | "prefix" -> Some (Pkg Prefix)
        | "user" -> Some (Pkg User)
@@ -484,6 +499,7 @@ let encode_to_latest_dune_lang_version t =
        | Corrected_suffix -> Some "corrected-suffix"
        | Inline_tests -> Some "inline_tests"
        | Toolchain -> Some "toolchain"
+       | Os os -> Some (Var.Os.to_string os)
        | Pkg pkg -> Some (Var.Pkg.encode_to_latest_dune_lang_version pkg)
      with
      | None -> Pform_was_deleted
@@ -554,10 +570,10 @@ module Env = struct
     let vars =
       let pkg =
         [ "switch", Var.Pkg.Switch
-        ; "os", Os
-        ; "os_version", Os_version
-        ; "os_distribution", Os_distribution
-        ; "os_family", Os_family
+        ; "os", Os Os
+        ; "os_version", Os Os_version
+        ; "os_distribution", Os Os_distribution
+        ; "os_family", Os Os_family
         ; "build", Build
         ; "prefix", Prefix
         ; "user", User
@@ -685,7 +701,11 @@ module Env = struct
         ; "toolchains", since ~version:(3, 0) Var.Toolchain
         ]
       in
-      String.Map.of_list_exn (List.concat [ lowercased; uppercased; other ])
+      let os =
+        List.map Var.Os.all ~f:(fun v ->
+          Var.Os.to_string v, since ~version:(3, 20) (Var.Os v))
+      in
+      String.Map.of_list_exn (List.concat [ lowercased; uppercased; other; os ])
     in
     fun syntax_version -> { syntax_version; vars; macros }
   ;;

src/dune_lang/pform.mli

@@ -2,6 +2,14 @@ open Import
 module Payload = Template.Pform.Payload
 
 module Var : sig
+  module Os : sig
+    type t =
+      | Os
+      | Os_version
+      | Os_distribution
+      | Os_family
+  end
+
   module Pkg : sig
     module Section : sig
       type t =
@@ -21,10 +29,7 @@ module Var : sig
 
     type t =
       | Switch
-      | Os
-      | Os_version
-      | Os_distribution
-      | Os_family
+      | Os of Os.t
       | Build
       | Prefix
       | User
@@ -69,6 +74,7 @@ module Var : sig
     | Profile
     | Context_name
     | Os_type
+    | Os of Os.t
     | Architecture
     | Arch_sixtyfour
     | System

src/dune_rules/expander.ml

@@ -516,6 +516,10 @@ let expand_pform_var (context : Context.t) ~dir ~source (var : Pform.Var.t) =
     (let+ ocaml = ocaml in
      lib_config_var var ocaml.lib_config)
     |> static
+  | Os v ->
+    static
+      (let+ v = Lock_dir.Sys_vars.(os poll v) in
+       [ Value.String (Option.value v ~default:"") ])
   | Ext_exe
   | Cpp
   | Pa_cpp

src/dune_rules/lock_dir.ml

@@ -13,6 +13,15 @@ module Sys_vars = struct
     ; sys_ocaml_version : string option Memo.Lazy.t
     }
 
+  let os t (v : Dune_lang.Pform.Var.Os.t) =
+    Memo.Lazy.force
+      (match v with
+       | Os -> t.os
+       | Os_version -> t.os_version
+       | Os_distribution -> t.os_distribution
+       | Os_family -> t.os_family)
+  ;;
+
   let poll =
     let vars =
       lazy

src/dune_rules/lock_dir.mli

@@ -20,6 +20,7 @@ module Sys_vars : sig
     ; sys_ocaml_version : string option Memo.Lazy.t
     }
 
+  val os : t -> Dune_lang.Pform.Var.Os.t -> string option Memo.t
   val poll : t
   val solver_env : unit -> Dune_pkg.Solver_env.t Memo.t
 end

src/dune_rules/pkg_rules.ml

@@ -3,7 +3,6 @@ open Memo.O
 
 include struct
   open Dune_pkg
-  module Sys_poll = Sys_poll
   module Package_variable = Package_variable
   module Substs = Substs
   module Checksum = Checksum
@@ -642,10 +641,10 @@ module Action_expander = struct
     let expand_pkg (paths : Path.t Paths.t) (pform : Pform.Var.Pkg.t) =
       match pform with
       | Switch -> Memo.return [ Value.String "dune" ]
-      | Os -> sys_poll_var (fun { os; _ } -> os)
-      | Os_version -> sys_poll_var (fun { os_version; _ } -> os_version)
-      | Os_distribution -> sys_poll_var (fun { os_distribution; _ } -> os_distribution)
-      | Os_family -> sys_poll_var (fun { os_family; _ } -> os_family)
+      | Os Os -> sys_poll_var (fun { os; _ } -> os)
+      | Os Os_version -> sys_poll_var (fun { os_version; _ } -> os_version)
+      | Os Os_distribution -> sys_poll_var (fun { os_distribution; _ } -> os_distribution)
+      | Os Os_family -> sys_poll_var (fun { os_family; _ } -> os_family)
       | Sys_ocaml_version ->
         sys_poll_var (fun { sys_ocaml_version; _ } -> sys_ocaml_version)
       | Build -> Memo.return [ Value.Dir paths.source_dir ]

test/blackbox-tests/test-cases/os-variables.t

@@ -0,0 +1,16 @@
+Demonstrate the following variables: %{os}, %{os_version}, %{os_distribution}, %{os_family}
+
+  $ cat >dune-project <<EOF
+  > (lang dune 3.20)
+  > EOF
+
+  $ cat >dune <<EOF
+  > (rule (write-file out "%{os}\n%{os_version}\n%{os_distribution}\n%{os_family}\n"))
+  > EOF
+
+  $ dune build out
+
+The values are not going to be portable, so we just count how many we get:
+
+  $ grep -c '.' _build/default/out
+  4