Fix #759

CHANGES.md

@@ -31,6 +31,9 @@ next
 - Display a better error messages when writing `(inline_tests)` in an
   executable stanza (#748, @diml)
 
+- Restore promoted files when they are deleted or changed in the
+  source tree (#760, fix #759, @diml)
+
 1.0+beta20 (10/04/2018)
 -----------------------
 

src/build_system.ml

@@ -753,6 +753,7 @@ let rec compile_rule t ?(copy_source=false) pre_rule =
       !Clflags.force &&
       List.exists targets_as_list ~f:Path.is_alias_stamp_file
     in
+    begin
       if deps_or_rule_changed || targets_missing || force then begin
         List.iter targets_as_list ~f:Path.unlink_no_err;
         pending_targets := Pset.union targets !pending_targets;
@@ -781,20 +782,25 @@ let rec compile_rule t ?(copy_source=false) pre_rule =
         Option.iter sandbox_dir ~f:Path.rm_rf;
         (* All went well, these targets are no longer pending *)
         pending_targets := Pset.diff !pending_targets targets;
-      clear_targets_digests_after_rule_execution targets_as_list;
-      (match mode with
+        clear_targets_digests_after_rule_execution targets_as_list
+      end else
+        Fiber.return ()
+    end >>| fun () ->
+    begin
+      match mode with
       | Standard | Fallback | Not_a_rule_stanza | Ignore_source_files -> ()
       | Promote | Promote_but_delete_on_clean ->
         Pset.iter targets ~f:(fun path ->
           let in_source_tree = Option.value_exn (Path.drop_build_context path) in
+          if not (Path.exists in_source_tree) ||
+             (Utils.Cached_digest.file path <>
+              Utils.Cached_digest.file in_source_tree) then begin
             if mode = Promote_but_delete_on_clean then
               Promoted_to_delete.add in_source_tree;
-           Io.copy_file ~src:path ~dst:in_source_tree));
+            Io.copy_file ~src:path ~dst:in_source_tree
+          end)
+    end;
     t.hook Rule_completed
-    end else begin
-      t.hook Rule_completed;
-      Fiber.return ()
-    end
   in
   let rule =
     { Internal_rule.

test/blackbox-tests/test-cases/github759/run.t

@@ -6,9 +6,12 @@
   $ rm -f .merlin
   $ jbuilder build foo.cma
   $ cat .merlin
-  cat: .merlin: No such file or directory
-  [1]
+  B _build/default/.foo.objs
+  FLG -open Foo -w -40
+  S .
   $ echo toto > .merlin
   $ jbuilder build foo.cma
   $ cat .merlin
-  toto
+  B _build/default/.foo.objs
+  FLG -open Foo -w -40
+  S .