Add support for %{bin-available:...}

CHANGES.md

@@ -216,6 +216,8 @@ Unreleased
 - Add support for `(empty_module_interface_if_absent)` in executable and library
   stanzas. (#4955, @nojb)
 
+- Add support for `%{bin-available:...}` (#4995, @jeremiedimino)
+
 2.9.1 (07/09/2021)
 ------------------
 

doc/concepts.rst

@@ -202,6 +202,8 @@ In addition, ``(action ...)`` fields support the following special variables:
   %{bin:program} ...)`` and ``(run program ...)`` behave in the same
   way. ``%{bin:...}`` is only necessary when you are using ``(bash
   ...)`` or ``(system ...)``
+- ``bin-available:<program>`` expands to ``true`` or ``false`` depending
+  on whether ``<program>`` is available or not.
 - ``lib:<public-library-name>:<file>`` expands to the installation path of
   the file ``<file>`` in the library ``<public-library-name>``. If
   ``<public-library-name>`` is available in the current workspace, the local

src/dune_engine/pform.ml

@@ -137,6 +137,7 @@ module Macro = struct
         ; lib_private : bool
         }
     | Lib_available
+    | Bin_available
     | Version
     | Read
     | Read_strings
@@ -165,6 +166,9 @@ module Macro = struct
     | Lib_available, Lib_available -> Eq
     | Lib_available, _ -> Lt
     | _, Lib_available -> Gt
+    | Bin_available, Bin_available -> Eq
+    | Bin_available, _ -> Lt
+    | _, Bin_available -> Gt
     | Version, Version -> Eq
     | Version, _ -> Lt
     | _, Version -> Gt
@@ -200,6 +204,7 @@ module Macro = struct
             [ ("lib_exec", bool lib_exec); ("lib_private", bool lib_private) ]
         ]
     | Lib_available -> string "Lib_available"
+    | Bin_available -> string "Bin_available"
     | Version -> string "Version"
     | Read -> string "Read"
     | Read_strings -> string "Read_strings"
@@ -302,6 +307,7 @@ let encode_to_latest_dune_lang_version t =
       | Lib { lib_exec = false; lib_private = true } -> Some "lib-private"
       | Lib { lib_exec = true; lib_private = true } -> Some "libexec-private"
       | Lib_available -> Some "lib-available"
+      | Bin_available -> Some "bin-available"
       | Version -> Some "version"
       | Read -> Some "read"
       | Read_strings -> Some "read-strings"
@@ -388,6 +394,7 @@ module Env = struct
            , since ~version:(2, 1)
                (Macro.Lib { lib_exec = true; lib_private = true }) )
          ; ("lib-available", macro Lib_available)
+         ; ("bin-available", since ~version:(3, 0) Macro.Bin_available)
          ; ("version", macro Version)
          ; ("read", macro Read)
          ; ("read-lines", macro Read_lines)

src/dune_engine/pform.mli

@@ -77,6 +77,7 @@ module Macro : sig
         ; lib_private : bool
         }
     | Lib_available
+    | Bin_available
     | Version
     | Read
     | Read_strings

src/dune_rules/artifacts.ml

@@ -25,6 +25,18 @@ module Bin = struct
             (let context = t.context.name in
              Action.Prog.Not_found.create ~program:name ?hint ~context ~loc ()))
 
+  let binary_available t name =
+    if not (Filename.is_relative name) then
+      let p = Path.of_filename_relative_to_initial_cwd name in
+      Fs_memo.path_exists p
+    else
+      match String.Map.find t.local_bins name with
+      | Some _ -> Memo.Build.return true
+      | None -> (
+        t.context.which name >>| function
+        | Some _ -> true
+        | None -> false)
+
   let add_binaries t ~dir l =
     let local_bins =
       List.fold_left l ~init:t.local_bins ~f:(fun acc fb ->

src/dune_rules/artifacts.mli

@@ -14,6 +14,8 @@ module Bin : sig
     -> string
     -> Action.Prog.t Memo.Build.t
 
+  val binary_available : t -> string -> bool Memo.Build.t
+
   val add_binaries : t -> dir:Path.Build.t -> File_binding.Expanded.t list -> t
 end
 

src/dune_rules/expander.ml

@@ -564,6 +564,13 @@ let expand_pform_gen ~(context : Context.t) ~bindings ~dir ~source
                let open Memo.Build.O in
                let+ available = Lib.DB.available (Scope.libs t.scope) lib in
                available |> string_of_bool |> string))
+      | Bin_available ->
+        Need_full_expander
+          (fun t ->
+            Without
+              (let open Memo.Build.O in
+              let+ b = Artifacts.Bin.binary_available t.bin_artifacts_host s in
+              b |> string_of_bool |> string))
       | Read ->
         let path = relative ~source dir s in
         Direct

test/blackbox-tests/test-cases/bin-available.t

@@ -0,0 +1,23 @@
+Test for %{bin-available:...}
+
+  $ cat >dune-project <<"EOF"
+  > (lang dune 3.0)
+  > (package (name foo))
+  > EOF
+  $ cat >dune<<"EOF"
+  > (rule
+  >  (alias default)
+  >  (action
+  >   (progn
+  >    (echo "dune: %{bin-available:dune}\n")
+  >    (echo "local program foo: %{bin-available:foo}\n")
+  >    (echo "non existant program: %{bin-available:*}\n"))))
+  > 
+  > (executable (public_name foo))
+  > EOF
+  $ touch foo.ml
+
+  $ dune build
+  dune: true
+  local program foo: true
+  non existant program: false