[m-rev.] for review: Compute touched .int0 files for nested submodules correctly

[Peter Wang]

Compute touched .int0 files for nested submodules correctly.

Since commit 25f8a6cc999ebcfaa8caf6c6e0af42b57503301b, we only write
private interface files (.int0) for modules that actually have child
modules. However, find_files_maybe_touched_by_process_module still
returned a list of "touched" .int0 files for all nested submodules of
the top module, including submodules that do not have child modules.

Each time mmc --make is run, it would check for those unwritten .int0 as
dependencies, conclude that they were not up-to-date, and try to
generate them again (as part of generating the .int0 file for the
top module).

compiler/make.module_target.m:
    Make find_files_maybe_touched_by_process_module exclude .int0 files
    for nested submodules without child modules.
---
 compiler/make.module_target.m | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/compiler/make.module_target.m b/compiler/make.module_target.m
index 97c5b8253..429e125ca 100644
--- a/compiler/make.module_target.m
+++ b/compiler/make.module_target.m
@@ -1059,6 +1059,15 @@
find_files_maybe_touched_by_process_module(ProgressStream, Globals,
         TouchedTargetFiles0 = make_target_file_list(TargetModuleNames,
             TargetType),
         TouchedTargetFiles = TouchedTargetFiles0 ++ HeaderTargets
+    ;
+        Task = task_make_int0,
+        ForeignCodeFiles = [],
+        % TouchedTargetFiles must only include modules with children, as we
+        % no longer write out private interface files for modules without
+        % children.
+        list.filter_map(is_ancestor_module, ModuleDepInfos, AncestorModules),
+        TouchedTargetFiles =
+            make_target_file_list(AncestorModules, TargetType)
     ;
         Task = task_make_int12,
         % Both long and short interface files are produced
@@ -1069,7 +1078,6 @@
find_files_maybe_touched_by_process_module(ProgressStream, Globals,
             make_target_file_list(TargetModuleNames, module_target_int2)
     ;
         ( Task = task_errorcheck
-        ; Task = task_make_int0
         ; Task = task_make_int3
         ; Task = task_make_opt
         ; Task = task_make_analysis_registry
@@ -1083,6 +1091,13 @@
find_files_maybe_touched_by_process_module(ProgressStream, Globals,
         TouchedTargetFiles, [], TimestampFileNames, !IO),
     TouchedFileNames = ForeignCodeFiles ++ TimestampFileNames.

+:- pred is_ancestor_module(module_dep_info::in, module_name::out) is semidet.
+
+is_ancestor_module(ModuleDepInfo, ModuleName) :-
+    module_dep_info_get_children(ModuleDepInfo, Children),
+    not set.is_empty(Children),
+    module_dep_info_get_module_name(ModuleDepInfo, ModuleName).
+
 :- pred gather_target_file_timestamp_file_names(globals::in, target_file::in,
     list(string)::in, list(string)::out, io::di, io::uo) is det.

-- 
2.42.0