From 4e1c23abec65a62fbd8e1ff16fffb619d5608881 Mon Sep 17 00:00:00 2001
From: Fred Hebert <mononcqc@ferd.ca>
Date: Sat, 14 Mar 2020 19:48:44 +0000
Subject: [PATCH] Fix Artifact tagging in DAG

The propagation was confusing source files and artifacts; the artifact
ordering was flipped, and the tagging non-mandatory (aside from as
edges), which made things hard to identify when plugins for compilers
are used.
---
 src/rebar_compiler.erl       |  4 ++--
 src/rebar_compiler_dag.erl   | 18 ++++++++++++------
 src/rebar_compiler_erl.erl   |  2 +-
 test/rebar_compile_SUITE.erl |  2 +-
 4 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/src/rebar_compiler.erl b/src/rebar_compiler.erl
index ccc0e160..8b83ec5a 100644
--- a/src/rebar_compiler.erl
+++ b/src/rebar_compiler.erl
@@ -246,8 +246,8 @@ store_artifacts(_G, []) ->
     ok;
 store_artifacts(G, [{Source, Target, Meta}|Rest]) ->
     %% Assume the source exists since it was tracked to be compiled
-    digraph:add_vertex(G, Target, Meta),
-    digraph:add_edge(G, Source, Target, artifact),
+    digraph:add_vertex(G, Target, {artifact, Meta}),
+    digraph:add_edge(G, Target, Source, artifact),
     store_artifacts(G, Rest).
 
 compile_worker(QueuePid, Opts, Config, Outs, CompilerMod) ->
diff --git a/src/rebar_compiler_dag.erl b/src/rebar_compiler_dag.erl
index 884bc847..a80ce5c5 100644
--- a/src/rebar_compiler_dag.erl
+++ b/src/rebar_compiler_dag.erl
@@ -233,7 +233,7 @@ maybe_rm_artifact_and_edge(G, OutDir, SrcExt, Ext, Source) ->
             %% Actually exists, don't delete
             false;
         false ->
-            Edges = digraph:out_edges(G, Source),
+            Edges = digraph:in_edges(G, Source),
             Targets = [V2 || Edge <- Edges,
                              {_E, _V1, V2, artifact} <- [digraph:edge(G, Edge)]],
             case Targets of
@@ -281,8 +281,7 @@ prepopulate_deps(G, Compiler, InDirs, Source, DepOpts, Status) ->
     %% drop edges from deps that aren't included!
     [digraph:del_edge(G, Edge) || Status == old,
                                   Edge <- digraph:out_edges(G, Source),
-                                  {_, _Src, Path, Label} <- [digraph:edge(G, Edge)],
-                                  Label =/= artifact,
+                                  {_, _Src, Path, _Label} <- [digraph:edge(G, Edge)],
                                   not lists:member(Path, AbsIncls)],
     %% Add the rest
     [digraph:add_edge(G, Source, Incl) || Incl <- AbsIncls],
@@ -296,11 +295,14 @@ refresh_dep(G, File) ->
             %% Gone! Erase from the graph
             digraph:del_vertex(G, File),
             mark_dirty(G);
+        {artifact, _} ->
+            %% ignore artifacts
+            ok;
         LastModified when LastUpdated < LastModified ->
             digraph:add_vertex(G, File, LastModified),
             mark_dirty(G);
         _ ->
-            % unchanged
+            %% unchanged
             ok
     end.
 
@@ -310,14 +312,18 @@ refresh_dep(G, File) ->
 propagate_stamps(_G, []) ->
     ok;
 propagate_stamps(G, [File|Files]) ->
-    Stamps = [element(2, digraph:vertex(G, F))
-              || F <- digraph:out_neighbours(G, File)],
+    Stamps = [Stamp
+              || F <- digraph:out_neighbours(G, File),
+                 {_, Stamp} <- [digraph:vertex(G, F)],
+                 is_tuple(Stamp) andalso element(1, Stamp) =/= artifact],
     case Stamps of
         [] ->
             ok;
         _ ->
             Max = lists:max(Stamps),
             case digraph:vertex(G, File) of
+                {_, {artifact, _}} ->
+                    ok;
                 {_, Smaller} when Smaller < Max ->
                     digraph:add_vertex(G, File, Max);
                 _ ->
diff --git a/src/rebar_compiler_erl.erl b/src/rebar_compiler_erl.erl
index bc80e275..86d6b4fb 100644
--- a/src/rebar_compiler_erl.erl
+++ b/src/rebar_compiler_erl.erl
@@ -235,7 +235,7 @@ opts_changed(Graph, NewOpts, Target, TargetBase) ->
         false -> NewOpts
     end,
     TargetOpts = case digraph:vertex(Graph, Target) of
-        {_Target, Opts} -> % tracked dep is found
+        {_Target, {artifact, Opts}} -> % tracked dep is found
             Opts;
         false -> % not found; might be a non-tracked DAG
             case compile_info(TargetBase) of
diff --git a/test/rebar_compile_SUITE.erl b/test/rebar_compile_SUITE.erl
index c121bd7e..55e0cda5 100644
--- a/test/rebar_compile_SUITE.erl
+++ b/test/rebar_compile_SUITE.erl
@@ -939,7 +939,7 @@ recompile_when_dag_opts_change(Config) ->
     DepsDir = filename:join([AppDir, "_build", "default", "lib"]),
     G = rebar_compiler_dag:init(DepsDir, rebar_compiler_erl, "project_apps", []),
     %% change the config in the DAG...
-    [digraph:add_vertex(G, Beam, [{d, some_define}]) || Beam <- Beams],
+    [digraph:add_vertex(G, Beam, {artifact, [{d, some_define}]}) || Beam <- Beams],
     digraph:add_vertex(G, '$r3_dirty_bit', true), % trigger a save
     rebar_compiler_dag:maybe_store(G, DepsDir, rebar_compiler_erl, "project_apps", []),
     rebar_compiler_dag:terminate(G),