add the "link" tag to "pack" actions (fixes #272)

Instead of a separate category, "pack" is now another form of linking
like "program", "library", "toplevel" and "output_obj". This fixes the
issue that package(...) tags where not passed at pack-production time,
spotted by Jérémie Dimino in
  <ocaml/opam-repository#11628 (comment)>
  <janestreet/ppx_sexp_conv#20>
More generally, this extends the meaning of all "link" flags to
"pack", which seems to be the correct behavior for all the rules we
inspected.

I tested that this change fixes the original 'nocrypto' issue
(once their _tags is also fixed to provide the right package(..)
option at pack-time).

This is a somewhat invasive change to the behavior of "pack" and
"link" tags, which may affect all user-defined flag declarations. An
alternative to this change would be to just add a specific "package"
rule when the "pack" tag is present, but my understanding is that
linking options quite generally apply to "pack" productions
(that really behave mostly like library-archive production already
under the ("link";"library") regime), so this more invasive change is
more correct: the extra cases where it applies were likely to be small
bugs before.

(I checked that ocb-stubblr is orthogonal to this change and does not
need any update.)

Changes

@@ -22,6 +22,15 @@ NEXT_RELEASE:
   custom, debug, failsafe, linkall, ccopt(..), cclib(..), rpath(..), ldopt(..)
   (Gabriel Scherer, report by Hannes Mehnert, review by whitequark)
 
+- #272: add the "link" tag to "pack" actions
+  Instead of a separate category, "pack" is now another form of linking
+  like "program", "library", "toplevel" and "output_obj". This fixes
+  the issue that package(...) tags where not passed at pack-production
+  time, spotted by Jérémie Dimino. More generally, this extends
+  the meaning of all "link" flags to "pack", which seems to be the correct
+  behavior for all the rules we inspected.
+  (Gabriel Scherer, original issue diagnosis by Jérémie Dimino)
+
 0.12.0 (11 Nov 2017):
 ---------------------
 

src/ocaml_compiler.ml

@@ -378,26 +378,26 @@ let byte_debug_library_link_mllib = link_from_file byte_debug_library_link_modul
 
 let byte_pack_modules =
   pack_modules [("cmo",["cmi"]); ("cmi",[])] "cmo" "cma" "cma" ocamlc_p
-    (fun tags -> tags++"ocaml"++"pack"++"byte")
+    (fun tags -> tags++"ocaml"++"link"++"byte"++"pack")
 
 let byte_pack_mlpack = link_from_file byte_pack_modules
 
 let byte_debug_pack_modules =
   pack_modules [("d.cmo",["cmi"]); ("cmi",[])] "d.cmo" "d.cma" "d.cma" ocamlc_p
-    (fun tags -> tags++"ocaml"++"pack"++"byte"++"debug")
+    (fun tags -> tags++"ocaml"++"link"++"byte"++"pack"++"debug")
 
 let byte_debug_pack_mlpack = link_from_file byte_debug_pack_modules
 
 let native_pack_modules x =
   pack_modules [("cmx",["cmi"; !Options.ext_obj]); ("cmi",[])] "cmx" "cmxa" !Options.ext_lib ocamlopt_p
-    (fun tags -> tags++"ocaml"++"pack"++"native") x
+    (fun tags -> tags++"ocaml"++"link"++"native"++"pack") x
 
 let native_pack_mlpack = link_from_file native_pack_modules
 
 let native_profile_pack_modules x =
   pack_modules [("p.cmx",["cmi"; "p" -.- !Options.ext_obj]); ("cmi",[])] "p.cmx" "p.cmxa"
     ("p" -.- !Options.ext_lib) ocamlopt_p
-    (fun tags -> tags++"ocaml"++"pack"++"native"++"profile") x
+    (fun tags -> tags++"ocaml"++"link"++"native"++"pack"++"profile") x
 
 let native_profile_pack_mlpack = link_from_file native_profile_pack_modules