From 1e18a5ec51543938a8f4ab0a2eb1fb8ee7378345 Mon Sep 17 00:00:00 2001
From: Stephen Sherratt <stephen@sherra.tt>
Date: Thu, 15 Dec 2022 16:06:21 +1100
Subject: [PATCH] In dune init proj set workspace root to proj dir

Signed-off-by: Stephen Sherratt <stephen@sherra.tt>
---
 CHANGES.md                                    |  3 ++
 bin/common.ml                                 |  4 ++
 bin/common.mli                                | 10 ++++
 bin/dune_init.ml                              |  7 +--
 bin/init.ml                                   | 34 ++++++++----
 .../config/config-in-workspace-file.t         |  2 +
 .../dune-init-proj-no-spurious-build-dir.t    | 54 +++++++++++++++++++
 .../test-cases/dune-init.t/run.t              | 15 ++++++
 8 files changed, 115 insertions(+), 14 deletions(-)
 create mode 100644 test/blackbox-tests/test-cases/dune-init-proj-no-spurious-build-dir.t

diff --git a/CHANGES.md b/CHANGES.md
index f9824eb5c1b7..691975812cac 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -53,6 +53,9 @@ Unreleased
 - Fix inline tests with js_of_ocaml and whole program compilation mode enabled
   (#6645, @hhugo)
 
+- Remove spurious build dir created when running `dune init proj ...` (#6707,
+  fixes #5429, @gridbugs)
+
 3.6.1 (2022-11-24)
 ------------------
 
diff --git a/bin/common.ml b/bin/common.ml
index 45a533b7e285..90759261710e 100644
--- a/bin/common.ml
+++ b/bin/common.ml
@@ -777,6 +777,8 @@ module Builder = struct
     ; react_to_insignificant_changes : bool
     }
 
+  let set_root t root = { t with root = Some root }
+
   let term =
     let docs = copts_sect in
     let+ config_from_command_line = shared_with_config_file
@@ -1220,6 +1222,8 @@ let term_with_default_root_is_cwd = term ~default_root_is_cwd:true
 
 let term = term ~default_root_is_cwd:false
 
+let build = build ~default_root_is_cwd:false
+
 let envs =
   Cmd.Env.
     [ info
diff --git a/bin/common.mli b/bin/common.mli
index 5c952156e7fe..e63c1d225557 100644
--- a/bin/common.mli
+++ b/bin/common.mli
@@ -86,3 +86,13 @@ module Let_syntax : sig
   val ( and+ ) :
     'a Cmdliner.Term.t -> 'b Cmdliner.Term.t -> ('a * 'b) Cmdliner.Term.t
 end
+
+module Builder : sig
+  type t
+
+  val set_root : t -> string -> t
+
+  val term : t Cmdliner.Term.t
+end
+
+val build : Builder.t -> t
diff --git a/bin/dune_init.ml b/bin/dune_init.ml
index 37efa0cf14c3..560759b991d1 100644
--- a/bin/dune_init.ml
+++ b/bin/dune_init.ml
@@ -457,12 +457,9 @@ module Component = struct
       in
       lib_target @ test_target
 
-    let proj
-        ({ context; common; options } as opts : Options.Project.t Options.t) =
+    let proj ({ common; options; _ } as opts : Options.Project.t Options.t) =
       let ({ template; pkg; _ } : Options.Project.t) = options in
-      let dir =
-        Path.relative context.dir (Dune_lang.Atom.to_string common.name)
-      in
+      let dir = Path.root in
       let name =
         Package.Name.parse_string_exn
           (Loc.none, Dune_lang.Atom.to_string common.name)
diff --git a/bin/init.ml b/bin/init.ml
index cf62a9f6402c..1397d5eca6b9 100644
--- a/bin/init.ml
+++ b/bin/init.ml
@@ -80,12 +80,13 @@ let common : Component.Options.Common.t Term.t =
   in
   { Component.Options.Common.name; libraries; pps }
 
-let context : Init_context.t Term.t =
+let path =
+  let docv = "PATH" in
+  Arg.(value & pos 1 (some string) None & info [] ~docv)
+
+let context_cwd : Init_context.t Term.t =
   let+ common_term = Common.term_with_default_root_is_cwd
-  and+ path =
-    let docv = "PATH" in
-    Arg.(value & pos 1 (some string) None & info [] ~docv)
-  in
+  and+ path = path in
   let config = Common.init common_term in
   Scheduler.go ~common:common_term ~config (fun () ->
       Memo.run (Init_context.make path))
@@ -116,7 +117,7 @@ let executable =
   let man = [] in
   let kind = "executable" in
   Cmd.v (Cmd.info kind ~doc ~man)
-  @@ let+ context = context
+  @@ let+ context = context_cwd
      and+ common = common
      and+ public = public in
      Component.init (Executable { context; common; options = { public } });
@@ -127,7 +128,7 @@ let library =
   let man = [] in
   let kind = "library" in
   Cmd.v (Cmd.info kind ~doc ~man)
-  @@ let+ context = context
+  @@ let+ context = context_cwd
      and+ common = common
      and+ public = public
      and+ inline_tests = inline_tests in
@@ -143,12 +144,13 @@ let test =
   let man = [] in
   let kind = "test" in
   Cmd.v (Cmd.info kind ~doc ~man)
-  @@ let+ context = context
+  @@ let+ context = context_cwd
      and+ common = common in
      Component.init (Test { context; common; options = () });
      print_completion kind common.name
 
 let project =
+  let module C = Common in
   let open Component.Options in
   let doc =
     "A project is a predefined composition of components arranged in a \
@@ -159,7 +161,8 @@ let project =
   in
   let man = [] in
   Cmd.v (Cmd.info "project" ~doc ~man)
-  @@ let+ context = context
+  @@ let+ common_builder = C.Builder.term
+     and+ path = path
      and+ common = common
      and+ inline_tests = inline_tests
      and+ template =
@@ -187,6 +190,19 @@ let project =
            & opt (some (enum Project.Pkg.commands)) None
            & info [ "pkg" ] ~docv ~doc)
      in
+     let context =
+       let init_context = Init_context.make path in
+       let name = Dune_lang.Atom.to_string common.name in
+       let root =
+         match path with
+         | Some path -> Filename.concat path name
+         | None -> name
+       in
+       let common = C.Builder.set_root common_builder root |> C.build in
+       let _ = Fpath.mkdir_p root in
+       let config = C.init common in
+       Scheduler.go ~common ~config (fun () -> Memo.run init_context)
+     in
      Component.init
        (Project { context; common; options = { template; inline_tests; pkg } });
      print_completion "project" common.name
diff --git a/test/blackbox-tests/test-cases/config/config-in-workspace-file.t b/test/blackbox-tests/test-cases/config/config-in-workspace-file.t
index e274783be65c..5dddf2a7324f 100644
--- a/test/blackbox-tests/test-cases/config/config-in-workspace-file.t
+++ b/test/blackbox-tests/test-cases/config/config-in-workspace-file.t
@@ -53,7 +53,9 @@ fields:
   > EOF
 
   $ dune init project foo
+  Entering directory 'foo'
   Success: initialized project component named foo
+  Leaving directory 'foo'
 
 But if we do the build we do get an error:
 
diff --git a/test/blackbox-tests/test-cases/dune-init-proj-no-spurious-build-dir.t b/test/blackbox-tests/test-cases/dune-init-proj-no-spurious-build-dir.t
new file mode 100644
index 000000000000..1af4db510cee
--- /dev/null
+++ b/test/blackbox-tests/test-cases/dune-init-proj-no-spurious-build-dir.t
@@ -0,0 +1,54 @@
+Ensure that running `dune init proj ...` doesn't create a spurious _build
+directory in the current directory.
+
+  $ dune init proj foo
+  Entering directory 'foo'
+  Success: initialized project component named foo
+  Leaving directory 'foo'
+  $ ls
+  foo
+  $ ls foo
+  _build
+  bin
+  dune-project
+  foo.opam
+  lib
+  test
+
+  $ dune init proj foo bar
+  Entering directory 'bar/foo'
+  Success: initialized project component named foo
+  Leaving directory 'bar/foo'
+  $ ls
+  bar
+  foo
+  $ ls bar
+  foo
+  $ ls bar/foo
+  _build
+  bar
+  bin
+  dune-project
+  foo.opam
+  lib
+  test
+
+  $ mkdir baz
+  $ dune init proj foo baz
+  Entering directory 'baz/foo'
+  Success: initialized project component named foo
+  Leaving directory 'baz/foo'
+  $ ls
+  bar
+  baz
+  foo
+  $ ls baz
+  foo
+  $ ls baz/foo
+  _build
+  baz
+  bin
+  dune-project
+  foo.opam
+  lib
+  test
diff --git a/test/blackbox-tests/test-cases/dune-init.t/run.t b/test/blackbox-tests/test-cases/dune-init.t/run.t
index fe1fd569b9c7..bd1ed44877e3 100644
--- a/test/blackbox-tests/test-cases/dune-init.t/run.t
+++ b/test/blackbox-tests/test-cases/dune-init.t/run.t
@@ -293,7 +293,9 @@ Initializing executable projects
 We can init a new executable project:
 
   $ dune init proj test_exec_proj
+  Entering directory 'test_exec_proj'
   Success: initialized project component named test_exec_proj
+  Leaving directory 'test_exec_proj'
 
 The generated project contains all expected sub-components:
 
@@ -301,6 +303,9 @@ The generated project contains all expected sub-components:
   test_exec_proj/dune-project
   test_exec_proj/test_exec_proj.opam
   
+  test_exec_proj/_build:
+  log
+  
   test_exec_proj/bin:
   dune
   main.ml
@@ -402,7 +407,9 @@ Initializing library projects
 We can init a new library project:
 
   $ dune init proj test_lib_proj --kind lib
+  Entering directory 'test_lib_proj'
   Success: initialized project component named test_lib_proj
+  Leaving directory 'test_lib_proj'
 
 The generated project contains all expected sub-components:
 
@@ -410,6 +417,9 @@ The generated project contains all expected sub-components:
   test_lib_proj/dune-project
   test_lib_proj/test_lib_proj.opam
   
+  test_lib_proj/_build:
+  log
+  
   test_lib_proj/lib:
   dune
   
@@ -504,7 +514,9 @@ Initializing projects using Esy
 We can init a project using Esy:
 
   $ dune init proj test_esy_proj --pkg esy
+  Entering directory 'test_esy_proj'
   Success: initialized project component named test_esy_proj
+  Leaving directory 'test_esy_proj'
 
 The esy project contains all expected sub-components:
 
@@ -512,6 +524,9 @@ The esy project contains all expected sub-components:
   test_esy_proj/dune-project
   test_esy_proj/package.json
   
+  test_esy_proj/_build:
+  log
+  
   test_esy_proj/bin:
   dune
   main.ml