chore: use with-dev-setup to manage opam test deps (#10744)

The goal is to simplify setting up the test dependencies. We use
`{with-dev-setup}` in `dune.opam`. By default, these dependencies are
not installed, but passing `--with-dev-setup` will install them.

Because the test dependencies are now expressed in an opam file, this is
more expressive, and it makes it possible to use opam filters to install
different dependencies on different configurations for example (#10712
is an example).

`make dev-deps` continues working as before, but it can now be expressed
as an opam command. `make dev-switch` is now an idempotent way to
keep the switch in sync (which should cover #6939 as it was reported).

Fixes #6939

Signed-off-by: Etienne Millon <me@emillon.org>

Makefile

@@ -6,25 +6,6 @@ DESTDIR_ARG := $(if $(DESTDIR),--destdir $(DESTDIR),)
 INSTALL_ARGS := $(PREFIX_ARG) $(LIBDIR_ARG) $(DESTDIR_ARG)
 BIN := ./_boot/dune.exe
 
-# Dependencies used for testing dune, when developed locally and
-# when tested in CI
-TEST_DEPS := \
-lwt \
-cinaps \
-"csexp>=1.3.0" \
-js_of_ocaml \
-js_of_ocaml-compiler \
-"mdx>=2.3.0" \
-menhir \
-ocamlfind \
-ocamlformat.$$(awk -F = '$$1 == "version" {print $$2}' .ocamlformat) \
-"odoc>=2.4.0" \
-"ppx_expect>=v0.16.0" \
-ppx_inline_test \
-ppxlib \
-ctypes \
-"utop>=2.6.0" \
-"melange>=4.0.0-414"
 # Dependencies recommended for developing dune locally,
 # but not wanted in CI
 DEV_DEPS := \
@@ -68,31 +49,33 @@ uninstall:
 .PHONY: reinstall
 reinstall: uninstall install
 
+.PHONY: install-ocamlformat
 install-ocamlformat:
 	opam install -y ocamlformat.$$(awk -F = '$$1 == "version" {print $$2}' .ocamlformat)
 
-dev-depext:
-	opam depext -y $(TEST_DEPS)
-
 .PHONY: dev-deps
-dev-deps:
-	opam install -y $(TEST_DEPS)
+dev-deps: install-ocamlformat
+	opam install -y . --deps-only --with-dev-setup
 
 .PHONY: coverage-deps
 coverage-deps:
 	opam install -y bisect_ppx
 
 .PHONY: dev-deps-sans-melange
-dev-deps-sans-melange:
-	opam install -y $(TEST_DEPS)
+dev-deps-sans-melange: dev-deps
 
 .PHONY: dev-switch
 dev-switch:
 	opam update
 # Ensuring that either a dev switch already exists or a new one is created
-	test "$(shell opam switch show)" = "$(shell pwd)" || \
-		opam switch create -y . $(TEST_OCAMLVERSION) --deps-only --with-test
-	opam install -y --update-invariant ocaml.$(TEST_OCAMLVERSION) $(TEST_DEPS) $(DEV_DEPS)
+	if test -d _opam ; then \
+		opam install -y --update-invariant ocaml.$(TEST_OCAMLVERSION); \
+	else \
+		opam switch create -y . $(TEST_OCAMLVERSION) --no-install ; \
+	fi
+	opam install -y . --deps-only --with-test --with-dev-setup
+	$(MAKE) install-ocamlformat
+	opam install -y $(DEV_DEPS)
 
 .PHONY: test
 test: $(BIN)

doc/hacking.rst

@@ -24,6 +24,12 @@ To create a directory-local opam switch with the dependencies necessary to build
 
   $ make dev-switch
 
+This can also be used to keep the switch updated when dependencies change.
+
+The ``Makefile`` also has a ``make dev-deps`` which will install just the
+dependencies used by tests. These are marked ``{ with-dev-setup }`` in Dune's
+opam file.
+
 Bootstrapping
 =============
 

dune.opam

@@ -46,4 +46,19 @@ depends: [
   ("ocaml" {>= "4.08"} | ("ocaml" {>= "4.02" & < "4.08~~"} & "ocamlfind-secondary"))
   "base-unix"
   "base-threads"
+  "lwt" { with-dev-setup & os != "win32" }
+  "cinaps" { with-dev-setup }
+  "csexp" { with-dev-setup & >= "1.3.0" }
+  "js_of_ocaml" { with-dev-setup & os != "win32" }
+  "js_of_ocaml-compiler" { with-dev-setup & os != "win32" }
+  "mdx" { with-dev-setup & >= "2.3.0" & os != "win32" }
+  "menhir" { with-dev-setup & os != "win32" }
+  "ocamlfind" { with-dev-setup & os != "win32" }
+  "odoc" { with-dev-setup & >= "2.4.0" & os != "win32" }
+  "ppx_expect" { with-dev-setup & >= "v0.16.0" & os != "win32" }
+  "ppx_inline_test" { with-dev-setup & os != "win32" }
+  "ppxlib" { with-dev-setup & os != "win32" }
+  "ctypes" { with-dev-setup & os != "win32" }
+  "utop" { with-dev-setup & >= "2.6.0" & os != "win32" }
+  "melange" { with-dev-setup & >= "4.0.0-414" & os != "win32" }
 ]

dune.opam.template

@@ -8,4 +8,19 @@ depends: [
   ("ocaml" {>= "4.08"} | ("ocaml" {>= "4.02" & < "4.08~~"} & "ocamlfind-secondary"))
   "base-unix"
   "base-threads"
+  "lwt" { with-dev-setup & os != "win32" }
+  "cinaps" { with-dev-setup }
+  "csexp" { with-dev-setup & >= "1.3.0" }
+  "js_of_ocaml" { with-dev-setup & os != "win32" }
+  "js_of_ocaml-compiler" { with-dev-setup & os != "win32" }
+  "mdx" { with-dev-setup & >= "2.3.0" & os != "win32" }
+  "menhir" { with-dev-setup & os != "win32" }
+  "ocamlfind" { with-dev-setup & os != "win32" }
+  "odoc" { with-dev-setup & >= "2.4.0" & os != "win32" }
+  "ppx_expect" { with-dev-setup & >= "v0.16.0" & os != "win32" }
+  "ppx_inline_test" { with-dev-setup & os != "win32" }
+  "ppxlib" { with-dev-setup & os != "win32" }
+  "ctypes" { with-dev-setup & os != "win32" }
+  "utop" { with-dev-setup & >= "2.6.0" & os != "win32" }
+  "melange" { with-dev-setup & >= "4.0.0-414" & os != "win32" }
 ]