Ensure dune version installed is appropriate (#1904)

* ensure dune version installed is appropriate

* add changelong

* Update src/dune.ml

Co-authored-by: Sonja Heinze <[email protected]>

* remove redundant

* dune release versions have only a numeric output so dont check for dune keyword

* log the dune version

* for pre relase and alpha versions, we should only extract numeric values

* bug fix, refactoring and logging

* use the dune with the features we want

* refactoring and bug fix

* Update src/dune.ml

Co-authored-by: Sonja Heinze <[email protected]>

* remove ai comments

* remove debugging artifacts

---------

Co-authored-by: Sonja Heinze <[email protected]>

Author: PizieDust

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Check that the dune version installed supports DPM (Dune Package Management).
+  Only if it does, add DPM to the list of available sandboxes. (#1904)
 - Fix DPM (Dune Package Management) support for users with Dune installed via
   Opam, Nix or similar. Previously, DPM support worked only when Dune was
   installed using the installation script for the Dune binary distribution. (#1903)

src/dune.ml

@@ -1,25 +1,69 @@
 open Import
 
+module Dune_version = struct
+  type t =
+    | Release of int * int * int
+    | Preview of int * int * int
+
+  let parse_release_version version_str =
+    let extract_int s =
+      let digits = String.filter s ~f:Char.is_digit in
+      if String.is_empty digits then None else Some (Int.of_string digits)
+    in
+    match String.split_on_chars ~on:[ '.' ] version_str with
+    | [ major; minor; patch ] ->
+      (match extract_int major, extract_int minor, extract_int patch with
+       | Some major, Some minor, Some patch_num ->
+         Some (Release (major, minor, patch_num))
+       | _ -> None)
+    | _ -> None
+  ;;
+
+  let parse_preview_version rest =
+    match String.split_on_chars ~on:[ ',' ] rest with
+    | timestamp_str :: _ ->
+      (try
+         Stdlib.Scanf.sscanf
+           (String.strip timestamp_str)
+           "%d-%d-%dT%d:%d:%dZ"
+           (fun y m d _h _min _s -> Some (Preview (y, m, d)))
+       with
+       | Stdlib.Scanf.Scan_failure _ | End_of_file -> None)
+    | _ -> None
+  ;;
+
+  let from_string str =
+    let prefix = "\"Dune Developer Preview: build " in
+    if String.is_prefix str ~prefix
+    then (
+      let rest = String.drop_prefix str (String.length prefix) in
+      match parse_preview_version rest with
+      | Some version -> Some version
+      | None -> parse_release_version str)
+    else parse_release_version str
+  ;;
+
+  (* Released versions >= 3.20.0 and preview versions with a timestamp on or
+     after 2025-07-30 support everything needed for VSCode to support DPM,
+     e.g. `dune lock`, `dune tools exec`, support of various Dune dev tools etc.
+     The last feature needed was implemented on 2025-07-29 and ensures that
+     other Dune dev tools (in particular ocamlformat) are included in the PATH
+     of the `ocamllsp` process. *)
+  let is_valid version =
+    match version with
+    | Release (major, minor, patch) ->
+      Stdlib.compare (major, minor, patch) (3, 20, 0) >= 0
+    | Preview (y, m, d) -> Stdlib.compare (y, m, d) (2025, 7, 30) >= 0
+  ;;
+end
+
 type t =
   { root : Path.t
   ; bin : Cmd.spawn
   }
 
 let binary = Path.of_string "dune"
 
-let make root () =
-  let open Promise.Syntax in
-  (* Should we do something specific for Windows ? *)
-  match root with
-  | Some root ->
-    let spawn = { Cmd.bin = binary; args = [] } in
-    let+ spawn = Cmd.check_spawn spawn in
-    (match spawn with
-     | Ok bin -> Some { bin; root }
-     | Error _ -> None)
-  | None -> Promise.return None
-;;
-
 let is_project_locked t =
   (* Path to the dune.lock dir *)
   let dune_lock_path = Path.join t.root (Path.of_string "dune.lock") in
@@ -50,3 +94,56 @@ let exec_tool ~tool ?(args = []) t =
 
 let equal d1 d2 = Path.equal d1.root d2.root
 let root t = t.root
+
+let make root () =
+  let open Promise.Syntax in
+  let dune_version_output bin root =
+    command { root; bin } ~args:[ "--version" ] |> Cmd.output ~cwd:root
+  in
+  (* Should we do something specific for Windows ? *)
+  match root with
+  | Some root ->
+    let spawn = { Cmd.bin = binary; args = [] } in
+    let* spawn = Cmd.check_spawn spawn in
+    (match spawn with
+     | Ok bin ->
+       let+ dune_version_output = dune_version_output bin root in
+       (match dune_version_output with
+        | Ok v ->
+          (match Dune_version.from_string v with
+           | Some version when Dune_version.is_valid version ->
+             show_message
+               `Info
+               "Dune Package Management selected with dune from %s, version %s."
+               (Path.to_string binary)
+               v;
+             Some { bin; root }
+           | _ -> None)
+        | Error _err -> None)
+     | Error _err ->
+       let* check_if_dune_is_installed_with_opam =
+         command
+           { root; bin = { Cmd.bin = Path.of_string "opam"; args = [] } }
+           ~args:[ "exec"; "--"; "which"; "dune" ]
+         |> Cmd.output ~cwd:root
+       in
+       (match check_if_dune_is_installed_with_opam with
+        | Error _err -> Promise.return None
+        | Ok path when String.is_empty path -> Promise.return None
+        | Ok path ->
+          let bin = { Cmd.bin = Path.of_string path; args = [] } in
+          let* dune_version_output = dune_version_output bin root in
+          (match dune_version_output with
+           | Ok v ->
+             (match Dune_version.from_string v with
+              | Some version when Dune_version.is_valid version ->
+                show_message
+                  `Info
+                  "Dune Package Management selected with dune from %s, version %s."
+                  path
+                  v;
+                Promise.return (Some { bin; root })
+              | _ -> Promise.return None)
+           | Error _err -> Promise.return None)))
+  | None -> Promise.return None
+;;