Add ${build-number}

Fix #255

CHANGES.md

@@ -35,6 +35,8 @@ next
 - Make sure modules in the current directory always have precedence
   over included directories (#597)
 
+- Add a `${build-number}` variable counting the number of builds. This
+  can be used to force running an action on every run of jbuilder
 
 1.0+beta18 (25/02/2018)
 -----------------------

doc/jbuild.rst

@@ -747,6 +747,10 @@ In addition, ``(action ...)`` fields support the following special variables:
   file
 - ``read-strings:<path>`` expands to the list of lines in the given
   file, unescaped using OCaml lexical convention
+- ``build-number`` expands to the number of times a build has been
+  started. This counter is reset when ``jbuilder clean`` is called. Using
+  this variable in an action will effectively cause it to be
+  executed everytime jbuilder runs
 
 The ``${<kind>:...}`` forms are what allows you to write custom rules that work
 transparently whether things are installed or not.

src/build_system.ml

@@ -339,7 +339,8 @@ type t =
   ; file_tree   : File_tree.t
   ; mutable local_mkdirs : Path.Local.Set.t
   ; mutable dirs : (Path.t, Dir_status.t) Hashtbl.t
-  ; mutable gen_rules : (dir:Path.t -> string list -> extra_sub_directories_to_keep) String_map.t
+  ; mutable gen_rules :
+      (dir:Path.t -> string list -> extra_sub_directories_to_keep) String_map.t
   ; mutable load_dir_stack : Path.t list
   ; (* Set of directories under _build that have at least one rule and
        all their ancestors. *)
@@ -1173,8 +1174,22 @@ let eval_request t ~request ~process_target =
        let dyn_deps = Build_exec.exec_nop t request () in
        process_targets (Pset.diff dyn_deps static_deps))
 
+let build_number_file = Path.relative Path.build_dir ".build-number"
+
+let increment_build_number t =
+  let fname = Path.to_string build_number_file in
+  let build_number =
+    if Sys.file_exists fname then
+      Sexp.Of_sexp.int (Sexp.load ~mode:Single ~fname) + 1
+    else
+      0
+  in
+  make_local_dirs t (Pset.singleton Path.build_dir);
+  Io.write_file fname (Sexp.to_string (Sexp.To_sexp.int build_number))
+
 let do_build t ~request =
   entry_point t ~f:(fun () ->
+    increment_build_number t;
     eval_request t ~request ~process_target:(wait_for_file t))
 
 module Ir_set = Set.Make(Internal_rule)

src/build_system.mli

@@ -159,6 +159,10 @@ val do_build
 
 (** {2 Other queries} *)
 
+(** File that contains the number of times {!do_build} was
+    called. This counter is resett by [jbuilder clean]. *)
+val build_number_file : Path.t
+
 val is_target : t -> Path.t -> bool
 
 (** Return all the library dependencies (as written by the user)

src/super_context.ml

@@ -537,6 +537,9 @@ module Action = struct
             | Alias -> Loc.fail loc "You cannot use ${@} in aliases."
             | Static l -> Some (Paths (l, Split))
           end
+        | "build-number" ->
+          add_ddep acc ~key
+            (Build.contents Build_system.build_number_file >>^ str_exp)
         | _ ->
           match String.lsplit2 var ~on:':' with
           | Some ("path-no-dep", s) ->

test/blackbox-tests/jbuild

@@ -408,3 +408,13 @@
      (progn
       (run ${exe:cram.exe} run.t)
       (diff? run.t run.t.corrected)))))))
+
+(alias
+ ((name runtest)
+  (deps ((files_recursively_in test-cases/build-number)))
+  (action
+   (chdir test-cases/build-number
+    (setenv JBUILDER ${bin:jbuilder}
+     (progn
+      (run ${exe:cram.exe} run.t)
+      (diff? run.t run.t.corrected)))))))

test/blackbox-tests/test-cases/build-number/jbuild

@@ -0,0 +1,3 @@
+(alias
+ ((name x)
+  (action (echo "Build number: ${build-number}"))))

test/blackbox-tests/test-cases/build-number/run.t

@@ -0,0 +1,10 @@
+  $ $JBUILDER build --root . -j 1 --display quiet @x
+  Build number: 0
+  $ $JBUILDER build --root . -j 1 --display quiet @x
+  Build number: 1
+  $ $JBUILDER build --root . -j 1 --display quiet @x
+  Build number: 2
+  $ $JBUILDER build --root . -j 1 --display quiet @x
+  Build number: 3
+  $ $JBUILDER build --root . -j 1 --display quiet @x
+  Build number: 4