tree: fix --no-switch option

Instead of emptying switch from it installed packages, load a virtual
switch at the beginning when `--no-switch` is given.

master_changes.md

@@ -45,6 +45,7 @@ users)
   * Allow packages with a specific version, directories or local opam files, as input [#5613 @kit-ty-kate]
   * Add handling of `--recurse` and `--subpath` for directory arguments [#5613 @kit-ty-kate]
   * Fix `--dev` option, force dev dependencies when option is given [#5687 @rjbou - fix #5675]
+  * Fix `--no-switch` option, instead of emptying switch from it installed packages, load a virtual switch at the beginning when `--no-switch` is given [#5687 @rjbou - fix #5675]
 
 ## Exec
 

src/client/opamCommands.ml

@@ -828,7 +828,12 @@ let tree ?(why=false) cli =
     else
       (apply_global_options cli global_options;
        OpamGlobalState.with_ `Lock_none @@ fun gt ->
-       OpamSwitchState.with_ `Lock_none gt @@ fun st ->
+       OpamRepositoryState.with_ `Lock_none gt @@ fun rt ->
+       (if no_switch then
+          fun k ->
+            k @@ OpamSwitchState.load_virtual gt rt
+        else
+          OpamSwitchState.with_ `Lock_none ~rt gt) @@ fun st ->
        let st, atoms =
          OpamAuxCommands.simulate_autopin
            st ~recurse ?subpath ~quiet:true
@@ -840,7 +845,7 @@ let tree ?(why=false) cli =
            depopts = false;
            build = true;
          } in
-       OpamTreeCommand.run st tog ~no_constraint ~no_switch mode filter atoms;
+       OpamTreeCommand.run st tog ~no_constraint mode filter atoms;
        `Ok ())
   in
   mk_command_ret ~cli (cli_from cli2_2) "tree" ~doc ~man

src/client/opamTreeCommand.ml

@@ -403,26 +403,7 @@ let dry_install tog st universe install =
   simulate_new_state tog st universe install
     (OpamPackage.Name.Set.of_list (List.map fst install))
 
-let raw_state tog st install =
-  let OpamListCommand.{doc; test; dev_setup; dev; _} = tog in
-  let names = OpamPackage.Name.Set.of_list (List.map fst install) in
-  let requested =
-    OpamPackage.packages_of_names
-      (Lazy.force st.available_packages)
-      names
-  in
-  let universe =
-    OpamSwitchState.universe st ~doc ~test ~dev_setup ~force_dev_deps:dev
-      ~requested Query
-  in
-  let universe =
-    { universe
-      with u_installed = OpamPackage.Set.empty;
-           u_installed_roots = OpamPackage.Set.empty }
-  in
-  simulate_new_state tog st universe install names
-
-let run st tog ?no_constraint ?(no_switch=false) mode filter atoms =
+let run st tog ?no_constraint mode filter atoms =
   let open OpamPackage.Set.Op in
   let select, missing =
     List.fold_left (fun (select, missing) atom ->
@@ -439,9 +420,6 @@ let run st tog ?no_constraint ?(no_switch=false) mode filter atoms =
     match mode, filter, missing with
     | Deps, _, [] -> st, universe
     | Deps, Roots_from, _::_ ->
-      if no_switch then
-        raw_state tog st missing
-      else
         dry_install tog st universe missing
     | Deps, Leads_to, _::_
     | ReverseDeps, _, _ ->
@@ -465,6 +443,6 @@ let run st tog ?no_constraint ?(no_switch=false) mode filter atoms =
   in
   print ?no_constraint forest;
   if OpamClientConfig.(!r.json_out) <> None then
-    (if not no_switch then
+    (if OpamSwitch.compare st.switch OpamSwitch.unset <> 0 then
        OpamJson.append "switch" (OpamSwitch.to_json st.switch);
      OpamJson.append "tree" (forest_to_json ?no_constraint forest))

src/client/opamTreeCommand.mli

@@ -34,6 +34,4 @@ val run :
   OpamListCommand.dependency_toggles ->
   (* output format options *)
   ?no_constraint:bool ->
-  (* do no keep switch consistency *)
-  ?no_switch:bool ->
   mode -> tree_filter -> OpamTypes.atom list -> unit

tests/reftests/json.unix.test

@@ -1302,6 +1302,13 @@ a.1
   ]
 }
 ### opam tree c --no-switch --json=out.json
+The following actions are simulated:
+=== install 4 packages
+  - install a       1 [required by c]
+  - install b       1 [required by c]
+  - install c       1
+  - install c-build 1 [required by c]
+
 c.1
 |-- a.1
 |-- b.1

tests/reftests/tree.test

@@ -303,10 +303,20 @@ l.1
 |-- a.1
 '-- l-dev.1
 ### opam tree l --no-switch
+The following actions are simulated:
+=== install 2 packages
+  - install a 1 [required by l]
+  - install l 1
+
 l.1
-|-- a.1
-'-- l-dev.1
+'-- a.1
 ### opam tree l --dev --no-switch
+The following actions are simulated:
+=== install 3 packages
+  - install a     1 [required by l]
+  - install l     1
+  - install l-dev 1 [required by l]
+
 l.1
 |-- a.1
 '-- l-dev.1 (dev)