Dev tool which command fails if tool not installed (ocaml#11922)

Previously `dune tool which` would print the path to where a dev tool
would be installed, regardless of whether it is currently installed.
This is inconsistent with how the `which` unix command works. This
commit changes its default behaviour to print an error and exit with
non-zero if the specified tool is not installed, allowing the command to
be used to check whether a given tool is currently inalled and bring it
into line with how `which` commands conventionally behave.

The original behaviour is preserved with the `--allow-not-installed`
flag.

Signed-off-by: Stephen Sherratt <[email protected]>

Author: gridbugs

bin/tools/ocamlformat.ml

@@ -1,8 +1,6 @@
 open! Import
 module Pkg_dev_tool = Dune_rules.Pkg_dev_tool
 
-let exe_path = Path.build @@ Pkg_dev_tool.exe_path Ocamlformat
-
 module Exec = struct
   let term =
     let+ builder = Common.Builder.term
@@ -23,18 +21,3 @@ module Exec = struct
 
   let command = Cmd.v info term
 end
-
-module Which = struct
-  let term =
-    let+ builder = Common.Builder.term in
-    let _ : Common.t * Dune_config_file.Dune_config.t = Common.init builder in
-    print_endline (Path.to_string exe_path)
-  ;;
-
-  let info =
-    let doc = {|Prints the path to the ocamlformat binary.|} in
-    Cmd.info "ocamlformat" ~doc
-  ;;
-
-  let command = Cmd.v info term
-end

bin/tools/ocamlformat.mli

@@ -3,7 +3,3 @@ open! Import
 module Exec : sig
   val command : unit Cmd.t
 end
-
-module Which : sig
-  val command : unit Cmd.t
-end

bin/tools/ocamllsp.ml

@@ -1,7 +1,6 @@
 open! Import
 module Pkg_dev_tool = Dune_rules.Pkg_dev_tool
 
-let ocamllsp_exe_path = Path.build @@ Pkg_dev_tool.exe_path Ocamllsp
 let ocamllsp_exe_name = Pkg_dev_tool.exe_name Ocamllsp
 
 let is_in_dune_project builder =
@@ -35,18 +34,3 @@ module Exec = struct
 
   let command = Cmd.v info term
 end
-
-module Which = struct
-  let term =
-    let+ builder = Common.Builder.term in
-    let _ : Common.t * Dune_config_file.Dune_config.t = Common.init builder in
-    print_endline (Path.to_string ocamllsp_exe_path)
-  ;;
-
-  let info =
-    let doc = "Prints the path to the ocamllsp binary." in
-    Cmd.info "ocamllsp" ~doc
-  ;;
-
-  let command = Cmd.v info term
-end

bin/tools/ocamllsp.mli

@@ -5,9 +5,3 @@ open! Import
 module Exec : sig
   val command : unit Cmd.t
 end
-
-(** Command to print ocamllsp's path if exists *)
-
-module Which : sig
-  val command : unit Cmd.t
-end

bin/tools/tools.ml

@@ -9,7 +9,10 @@ end
 module Which = struct
   let doc = "Command group for printing the path to wrapped tools."
   let info = Cmd.info ~doc "which"
-  let group = Cmd.group info [ Ocamlformat.Which.command; Ocamllsp.Which.command ]
+
+  let group =
+    Cmd.group info (List.map [ Ocamlformat; Ocamllsp ] ~f:Tools_common.which_command)
+  ;;
 end
 
 let doc = "Command group for wrapped tools."

bin/tools/tools_common.ml

@@ -54,3 +54,37 @@ let lock_build_and_run_dev_tool ~common ~config dev_tool ~args =
   lock_and_build_dev_tool ~common ~config dev_tool;
   run_dev_tool (Common.root common) dev_tool ~args
 ;;
+
+let which_command dev_tool =
+  let exe_path = dev_tool_exe_path dev_tool in
+  let exe_name = Pkg_dev_tool.exe_name dev_tool in
+  let term =
+    let+ builder = Common.Builder.term
+    and+ allow_not_installed =
+      Arg.(
+        value
+        & flag
+        & info
+            [ "allow-not-installed" ]
+            ~doc:
+              (sprintf
+                 "If %s is not installed as a dev tool, still print where it would be \
+                  installed."
+                 exe_name))
+    in
+    let _ : Common.t * Dune_config_file.Dune_config.t = Common.init builder in
+    if allow_not_installed || Path.exists exe_path
+    then print_endline (Path.to_string exe_path)
+    else User_error.raise [ Pp.textf "%s is not installed as a dev tool" exe_name ]
+  in
+  let info =
+    let doc =
+      sprintf
+        "Prints the path to the %s dev tool executable if it exists, errors out \
+         otherwise."
+        exe_name
+    in
+    Cmd.info exe_name ~doc
+  in
+  Cmd.v info term
+;;

bin/tools/tools_common.mli

@@ -9,3 +9,5 @@ val lock_build_and_run_dev_tool
   -> Dune_pkg.Dev_tool.t
   -> args:string list
   -> 'a
+
+val which_command : Dune_pkg.Dev_tool.t -> unit Cmd.t

test/blackbox-tests/test-cases/pkg/dev-tools-which.t

@@ -0,0 +1,34 @@
+Test `dune tools which ocamlformat`:
+  $ . ./helpers.sh
+  $ mkrepo
+
+  $ make_fake_ocamlformat "0.26.2"
+  $ make_ocamlformat_opam_pkg "0.26.2"
+  $ make_project_with_dev_tool_lockdir
+
+Update ".ocamlformat" file with unknown version of OCamlFormat.
+  $ cat > .ocamlformat <<EOF
+  > version = 0.26.2
+  > EOF
+
+The command will fail because the dev tool is not installed:
+  $ dune tools which ocamlformat
+  Error: ocamlformat is not installed as a dev tool
+  [1]
+
+  $ dune tools which ocamlformat --allow-not-installed
+  _build/_private/default/.dev-tool/ocamlformat/ocamlformat/target/bin/ocamlformat
+
+Install the dev tool:
+  $ dune tools exec ocamlformat
+  Solution for dev-tools.locks/ocamlformat:
+  - ocamlformat.0.26.2
+       Running 'ocamlformat'
+  formatted with version 0.26.2
+
+Now the command will succeed because the tool has been installed:
+  $ dune tools which ocamlformat
+  _build/_private/default/.dev-tool/ocamlformat/ocamlformat/target/bin/ocamlformat
+
+Make sure the file is actually there:
+  $ test -f $(dune tools which ocamlformat)