[opam] add `make opam.lock` target

Summary: Useful to update opam package versions.

Reviewed By: jberdine

Differential Revision: D5190763

fbshipit-source-id: 225462e

CONTRIBUTING.md

@@ -218,3 +218,14 @@ Follow `clang-format` (see ".clang-format" at the root of the repository).
 $ infer --debug -- clang -c examples/hello.c
 $ firefox infer-out/captured/hello.c.*.html
 ```
+
+## Updating opam and opam.lock
+
+tl; dr: Run `make opam.lock`.
+
+opam.lock records fixed versions of the opam dependencies known to work with infer and to respect
+the constraints in opam. This prevents unpredictable breakages of infer or its dependencies,
+especially for infer releases, for which it is more difficult to change their package constraints
+after the fact.
+
+To add an opam package or update its version constraints, edit 'opam' then run `make opam.lock`.

Makefile

@@ -518,6 +518,27 @@ conf-clean: clean
 	$(REMOVE_DIR) $(MODELS_DIR)/java/infer-out/
 	$(REMOVE_DIR) $(MODELS_DIR)/objc/out/
 
+
+# opam package to hold infer dependencies
+INFER_PKG_OPAMLOCK=infer-lock-deps
+
+# phony because it depends on opam's internal state
+.PHONY: opam.lock
+opam.lock: opam
+	$(QUIET)if test x"$$(git status --porcelain -- opam)" != "x"; then \
+	  echo "ERROR: Changes to 'opam' detected." 1>&2; \
+	  echo "ERROR: Please commit or revert your changes before updating opam.lock." 1>&2; \
+	  echo "ERROR: This is because opam.lock is generated from the HEAD commit." 1>&2; \
+	  exit 1; \
+	fi
+	$(QUIET)$(call silent_on_success,opam update,$(OPAM) update)
+	$(QUIET)$(call silent_on_success,installing dependencies $(INFER_PKG_OPAMLOCK) opam package,\
+	  OPAMSWITCH=$(OPAMSWITCH); \
+	  $(OPAM) pin add --yes --no-action -k git $(INFER_PKG_OPAMLOCK) .#HEAD; \
+	  $(OPAM) install --deps-only --yes infer)
+	$(QUIET)$(call silent_on_success,generating opam.lock,\
+	  $(OPAM) lock --pkg  $(INFER_PKG_OPAMLOCK) > opam.lock)
+
 # print any variable for Makefile debugging
 print-%:
 	$(QUIET)echo '$*=$($*)'

Makefile.autoconf.in

@@ -56,6 +56,8 @@ OCAMLC = @OCAMLC@
 OCAMLFIND = @OCAMLFIND@
 OCAMLLEX = @OCAMLLEX@
 OCAMLOPT = @OCAMLOPT@
+OPAM = @OPAM@
+OPAMSWITCH = @OPAMSWITCH@
 PATH = @PATH@
 prefix = @prefix@
 PYTHON_lxml = @PYTHON_lxml@

configure.ac

@@ -193,6 +193,14 @@ AC_ASSERT_PROG([rebuild], [$REBUILD])
 AC_ARG_VAR([CAML_LD_LIBRARY_PATH],
   [Additional directories to search for dynamically-loaded libraries.])
 
+
+AC_CHECK_TOOL([OPAM], [opam], [no])
+AS_IF([test "$OPAM" != "no"], [
+  AC_MSG_CHECKING([current opam switch])
+  OPAMSWITCH=$("$OPAM" switch show)
+  AC_MSG_RESULT([$OPAMSWITCH])
+])
+
 if test "x$enable_java_analyzers" = "xyes"; then
   AC_CHECK_TOOL([JAVA], [java], [no])
   AC_PATH_TOOL([JAVAC], [javac], [no])