fix(pkg): make dune pin itelf

Automatically make dune pin itself. We're going to assume that the dune
we're using right now is the one that will be used to run the build
plan.

Perhaps this behavior isn't always deired. We could imagine wanting to
produce build plans for older or newer dunes. For now, this is a good
default though.

Addresses #12381

Signed-off-by: Rudi Grinberg <[email protected]>

Author: rgrinberg

src/dune_pkg/dune_dep.ml

@@ -6,3 +6,6 @@ let version =
   let major, minor = Dune_lang.Stanza.latest_version in
   OpamPackage.Version.of_string @@ sprintf "%d.%d" major minor
 ;;
+
+let package = OpamPackage.create (Package_name.to_opam_package_name name) version
+let opam_file = OpamFile.OPAM.create package

src/dune_pkg/dune_dep.mli

@@ -1,2 +1,4 @@
 val name : Package_name.t
 val version : OpamPackage.Version.t
+val package : OpamPackage.t
+val opam_file : OpamFile.OPAM.t

src/dune_pkg/opam_solver.ml

@@ -348,6 +348,8 @@ module Context = struct
   let user_restrictions : t -> OpamPackage.Name.t -> OpamFormula.version_constraint option
     =
     fun t pkg ->
+    (* This isn't really needed because we already pin dune, but it seems to
+       help the error messages *)
     if Package_name.equal Dune_dep.name (Package_name.of_opam_package_name pkg)
     then Some (`Eq, t.dune_version)
     else None
@@ -1658,6 +1660,18 @@ let solve_lock_dir
       ~selected_depopts
       ~portable_lock_dir
   =
+  let pinned_packages =
+    Package_name.Map.update pinned_packages Dune_dep.name ~f:(function
+      | None -> Some Resolved_package.dune
+      | Some p ->
+        let loc = Resolved_package.loc p in
+        User_error.raise
+          ~loc
+          [ Pp.text
+              "Dune cannot be pinned. The currently running version is the only one that \
+               may be used"
+          ])
+  in
   let pinned_package_names = Package_name.Set.of_keys pinned_packages in
   let stats_updater = Solver_stats.Updater.init () in
   let context =

src/dune_pkg/resolved_package.ml

@@ -4,18 +4,39 @@ type extra_files =
   | Inside_files_dir of Path.t option
   | Git_files of Path.Local.t option * Rev_store.At_rev.t
 
-type nonrec t =
+type rest =
   { opam_file : OpamFile.OPAM.t
   ; package : OpamPackage.t
   ; extra_files : extra_files
   ; loc : Loc.t
   ; dune_build : bool
   }
 
-let dune_build t = t.dune_build
-let loc t = t.loc
-let package t = t.package
-let opam_file t = t.opam_file
+type nonrec t =
+  | Dune
+  | Rest of rest
+
+let dune = Dune
+
+let dune_build = function
+  | Dune -> false
+  | Rest t -> t.dune_build
+;;
+
+let loc = function
+  | Dune -> Loc.none
+  | Rest t -> t.loc
+;;
+
+let package = function
+  | Dune -> Dune_dep.package
+  | Rest t -> t.package
+;;
+
+let opam_file = function
+  | Dune -> Dune_dep.opam_file
+  | Rest t -> t.opam_file
+;;
 
 let add_opam_package_to_opam_file package opam_file =
   opam_file
@@ -37,12 +58,13 @@ let git_repo package ~opam_file ~opam_file_contents rev ~files_dir ~url =
   let opam_file_path = Path.of_local opam_file in
   let opam_file = read_opam_file package ~opam_file_path ~opam_file_contents ~url in
   let loc = Loc.in_file opam_file_path in
-  { dune_build = false
-  ; loc
-  ; package
-  ; opam_file
-  ; extra_files = Git_files (files_dir, rev)
-  }
+  Rest
+    { dune_build = false
+    ; loc
+    ; package
+    ; opam_file
+    ; extra_files = Git_files (files_dir, rev)
+    }
 ;;
 
 let local_fs package ~dir ~opam_file_path ~files_dir ~url =
@@ -53,12 +75,13 @@ let local_fs package ~dir ~opam_file_path ~files_dir ~url =
     read_opam_file package ~opam_file_path ~opam_file_contents ~url
   in
   let loc = Loc.in_file opam_file_path in
-  { dune_build = false
-  ; loc
-  ; package
-  ; extra_files = Inside_files_dir files_dir
-  ; opam_file
-  }
+  Rest
+    { dune_build = false
+    ; loc
+    ; package
+    ; extra_files = Inside_files_dir files_dir
+    ; opam_file
+    }
 ;;
 
 (* Scan a path recursively down retrieving a list of all files together with their
@@ -92,18 +115,26 @@ let local_package ~command_source loc opam_file opam_package =
   in
   let opam_file = add_opam_package_to_opam_file opam_package opam_file in
   let package = OpamFile.OPAM.package opam_file in
-  { dune_build; opam_file; package; loc; extra_files = Inside_files_dir None }
+  Rest { dune_build; opam_file; package; loc; extra_files = Inside_files_dir None }
 ;;
 
 open Fiber.O
 
 let get_opam_package_files resolved_packages =
   let indexed = List.mapi resolved_packages ~f:(fun i w -> i, w) |> Int.Map.of_list_exn in
   let from_dirs, from_git =
-    Int.Map.partition_map indexed ~f:(fun (resolved_package : t) ->
-      match resolved_package.extra_files with
-      | Git_files (files_dir, rev) -> Right (files_dir, rev)
-      | Inside_files_dir dir -> Left dir)
+    let _dune, without_dune =
+      Int.Map.partition_map indexed ~f:(function
+        | Dune -> Left ()
+        | Rest t -> Right t)
+    in
+    let dirs, git =
+      Int.Map.partition_map without_dune ~f:(fun (resolved_package : rest) ->
+        match resolved_package.extra_files with
+        | Git_files (files_dir, rev) -> Right (files_dir, rev)
+        | Inside_files_dir dir -> Left dir)
+    in
+    dirs, git
   in
   let+ from_git =
     if Int.Map.is_empty from_git

src/dune_pkg/resolved_package.mli

@@ -6,6 +6,7 @@ val package : t -> OpamPackage.t
 val opam_file : t -> OpamFile.OPAM.t
 val loc : t -> Loc.t
 val dune_build : t -> bool
+val dune : t
 
 val git_repo
   :  OpamPackage.t

test/blackbox-tests/test-cases/pkg/implicit-dune-constraint.t

@@ -17,19 +17,19 @@ dependency.
   Error: Unable to solve dependencies for the following lock directories:
   Lock directory dune.lock:
   Couldn't solve the package dependency formula.
-  The following packages couldn't be found: dune
+  Selected candidates: foo.0.0.1 x.dev
+  - dune -> (problem)
+      User requested = 3.XX
+      foo 0.0.1 requires <= 2.0.0
+      Rejected candidates:
+        dune.3.XX: Incompatible with restriction: <= 2.0.0
   $ test "4.0.0"
-  Error: Unable to solve dependencies for the following lock directories:
-  Lock directory dune.lock:
-  Couldn't solve the package dependency formula.
-  The following packages couldn't be found: dune
-  [1]
+  Solution for dune.lock:
+  - foo.0.0.1
 
   $ test "4.0.0" 2>&1 | sed -E 's/3.[0-9]+/3.XX/g'
-  Error: Unable to solve dependencies for the following lock directories:
-  Lock directory dune.lock:
-  Couldn't solve the package dependency formula.
-  The following packages couldn't be found: dune
+  Solution for dune.lock:
+  - foo.0.0.1
 
 Create a fake project and ensure `dune` can be used as a dependency:
   $ cat > dune-project <<EOF
@@ -40,8 +40,5 @@ Create a fake project and ensure `dune` can be used as a dependency:
   >  (depends dune))
   > EOF
   $ dune pkg lock
-  Error: Unable to solve dependencies for the following lock directories:
-  Lock directory dune.lock:
-  Couldn't solve the package dependency formula.
-  The following packages couldn't be found: dune
-  [1]
+  Solution for dune.lock:
+  (no dependencies to lock)

test/blackbox-tests/test-cases/pkg/pin-stanza/pin-dune.t

@@ -0,0 +1,34 @@
+Pinning dune itself
+
+  $ . ../helpers.sh
+
+  $ mkrepo
+  $ add_mock_repo_if_needed
+
+# CR-someday rgrinberg: ideally, this source shouldn't be necessary and we
+# should disqualify this pin without resolving any sources
+
+  $ mkdir _extra_source
+  $ cat >_extra_source/dune-project <<EOF
+  > (lang dune 3.12)
+  > (package (name dune))
+  > EOF
+
+  $ cat >dune-project <<EOF
+  > (lang dune 3.13)
+  > (pin
+  >  (url "file://$PWD/_extra_source")
+  >  (package (name dune)))
+  > (package
+  >   (name main))
+  > EOF
+
+For now, pinning dune is not allowed:
+
+  $ dune pkg lock
+  File "dune-project", line 4, characters 1-22:
+  4 |  (package (name dune)))
+       ^^^^^^^^^^^^^^^^^^^^^
+  Error: Dune cannot be pinned. The currently running version is the only one
+  that may be used
+  [1]

test/blackbox-tests/test-cases/pkg/unsatisfied-version-constraint-on-dune.t

@@ -22,8 +22,12 @@ project:
 
 Solve the dependencies:
   $ dune pkg lock 2>&1 | sed -E 's/"3.[0-9]+"/"3.XX"/'
-  Error: The current version of Dune does not satisfy the version constraints
-  for Dune in this project's dependencies.
-  Details:
-  Found version "3.XX" of package "dune" which doesn't satisfy the required
-  version constraint "< 3.0"
+  Error: Unable to solve dependencies for the following lock directories:
+  Lock directory dune.lock:
+  Couldn't solve the package dependency formula.
+  Selected candidates: foo.dev
+  - dune -> (problem)
+      User requested = 3.21
+      foo dev requires < 3.0
+      Rejected candidates:
+        dune.3.21: Incompatible with restriction: < 3.0