From 40159f52d15f01f08ee8705dce354c8dfd2090d2 Mon Sep 17 00:00:00 2001
From: Brujo Benavides <fernando.benavides@adroll.com>
Date: Fri, 21 May 2021 17:04:48 +0200
Subject: [PATCH] Fix #130: Avoid emitting a warning if an attribute is used
 only where it's defined (#131)

---
 src/rules/single_use_hrl_attrs.erl                | 15 +++++++++++----
 .../lib/app/include/header1.hrl                   |  3 ++-
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/rules/single_use_hrl_attrs.erl b/src/rules/single_use_hrl_attrs.erl
index f00582d..8fab9d3 100644
--- a/src/rules/single_use_hrl_attrs.erl
+++ b/src/rules/single_use_hrl_attrs.erl
@@ -28,11 +28,11 @@ analyze(FilesAndASTs, _Context) ->
     [build_macro_result(HrlFile, MacroKey, AttributesUsed)
      || {HrlFile, #{define := Defines}} <- HrlDefs,
         MacroKey <- Defines,
-        is_used_only_once(MacroKey, AttributesUsed)]
+        is_used_only_once(HrlFile, MacroKey, AttributesUsed)]
     ++ [build_record_result(HrlFile, RecordKey, AttributesUsed)
         || {HrlFile, #{record := Records}} <- HrlDefs,
            RecordKey <- Records,
-           is_used_only_once(RecordKey, AttributesUsed)].
+           is_used_only_once(HrlFile, RecordKey, AttributesUsed)].
 
 build_macro_result(HrlFile, {Macro, Line}, AttributesUsed) ->
     [File] = maps:get(Macro, AttributesUsed),
@@ -56,8 +56,15 @@ build_record_result(HrlFile, {Record, Line}, AttributesUsed) ->
       text => hank_utils:format_text("#~tp is used only at ~ts", [Record, File]),
       pattern => Record}.
 
-is_used_only_once({Key, _Line}, AttributesUsed) ->
-    length(maps:get(Key, AttributesUsed, [])) == 1.
+is_used_only_once(HrlFile, {Key, _Line}, AttributesUsed) ->
+    case maps:get(Key, AttributesUsed, []) of
+        [SingleFile] ->
+            %% There is nothing wrong with using an attribute only in the same
+            %% file where it's defined.
+            SingleFile /= HrlFile;
+        _ ->
+            false
+    end.
 
 file_using({File, FileAST}, CurrentFiles) ->
     AddFun = fun(Files) -> lists:usort([File | Files]) end,
diff --git a/test/files/single_use_hrl_attrs/lib/app/include/header1.hrl b/test/files/single_use_hrl_attrs/lib/app/include/header1.hrl
index 6fd6b2c..74410ed 100644
--- a/test/files/single_use_hrl_attrs/lib/app/include/header1.hrl
+++ b/test/files/single_use_hrl_attrs/lib/app/include/header1.hrl
@@ -1,3 +1,4 @@
 -define(APP_HEADER_1, "this is header from app that will be used in just one module").
 -define(SOME_MACRO_1(A), A).
--define(SOME_DEFINE, ok).
+-define(THIS_MACRO, {is_used, "and", it, shouldnt, generate, a, warning}).
+-define(SOME_DEFINE, ?THIS_MACRO).