From e644d7c078c9b75edf1ba513a030d33921af8192 Mon Sep 17 00:00:00 2001
From: Mikhail Uvarov <arcusfelis@gmail.com>
Date: Mon, 12 Aug 2019 01:49:59 +0200
Subject: Correctly render redefined variable

Rendering of variables behaves differently for already defined
variables.
Values of such variables are rendered in the wrong order,
ignoring any variables above from the same file.
---
 src/rlx_prv_overlay.erl    |  6 ++++--
 test/rlx_release_SUITE.erl | 12 ++++++++++--
 test/rlx_test_utils.erl    |  3 ++-
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/rlx_prv_overlay.erl b/src/rlx_prv_overlay.erl
index 87fa91f..75608b3 100644
--- a/src/rlx_prv_overlay.erl
+++ b/src/rlx_prv_overlay.erl
@@ -187,9 +187,11 @@ merge_overlay_vars(State, FileNames) ->
                                 %% to the current one being read
                                 OverlayRelativeRoot = filename:dirname(FileName),
                                 NewTerms = check_overlay_inclusion(State, OverlayRelativeRoot, Terms),
+                                %% Remove already defined variables from Acc,
+                                %% append NewTerms, preserving order
                                 lists:foldl(fun(NewTerm, A) ->
-                                                    lists:keystore(element(1, NewTerm), 1, A, NewTerm)
-                                            end, Acc, NewTerms);
+                                                    lists:keydelete(element(1, NewTerm), 1, A)
+                                            end, Acc, NewTerms) ++ NewTerms;
                             {error, Reason} ->
                                 ec_cmd_log:warn(rlx_state:log(State),
                                                 format_error({unable_to_read_varsfile, FileName, Reason})),
diff --git a/test/rlx_release_SUITE.erl b/test/rlx_release_SUITE.erl
index a582526..7ddaa14 100644
--- a/test/rlx_release_SUITE.erl
+++ b/test/rlx_release_SUITE.erl
@@ -781,14 +781,18 @@ overlay_release(Config) ->
                     goal_app_2]}]),
 
     VarsFile1 = filename:join([LibDir1, "vars1.config"]),
+    %% tpl_var is defined in vars1, but redifined in vars2 using template.
     rlx_test_utils:write_config(VarsFile1, [{yahoo, "yahoo"},
                                             {yahoo2, [{foo, "bar"}]},
                                             {foo_yahoo, "foo_{{yahoo}}"},
-                                            {foo_dir, "foodir"}]),
+                                            {foo_dir, "foodir"},
+                                            {tpl_var, "defined in vars1"}]),
 
     VarsFile2 = filename:join([LibDir1, "vars2.config"]),
     rlx_test_utils:write_config(VarsFile2, [{google, "yahoo"},
                                             {yahoo2, "foo"},
+                                            {tpl_arg, "a template value"},
+                                            {tpl_var, "Redefined in vars2 with {{tpl_arg}}"},
                                             OverlayVars3]),
 
     VarsFile3 = filename:join([LibDir1, "vars3.config"]),
@@ -857,7 +861,11 @@ overlay_release(Config) ->
     ?assertEqual("val1",
                  proplists:get_value(prop1, TemplateData)),
     ?assertEqual(2,
-                 proplists:get_value(prop2, TemplateData)).
+                 proplists:get_value(prop2, TemplateData)),
+    %% This should be rendered correctly based on VarsFile2 file, regardless
+    %% of tpl_var defined in VarsFile1 or not.
+    ?assertEqual("Redefined in vars2 with a template value",
+                 proplists:get_value(tpl_var, TemplateData)).
 
 make_goalless_release(Config) ->
     LibDir1 = proplists:get_value(lib1, Config),
diff --git a/test/rlx_test_utils.erl b/test/rlx_test_utils.erl
index 37d9c7a..5328559 100644
--- a/test/rlx_test_utils.erl
+++ b/test/rlx_test_utils.erl
@@ -185,7 +185,8 @@ test_template_contents() ->
         "{foo_yahoo, \"{{foo_yahoo}}\"}.\n"
         "{google, \"{{google}}\"}.\n"
         "{prop1, \"{{prop1}}\"}.\n"
-        "{prop2, {{prop2}}}.\n".
+        "{prop2, {{prop2}}}.\n"
+        "{tpl_var, \"{{tpl_var}}\"}.\n".
 
 escript_contents() ->
     "#!/usr/bin/env escript\n"
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