From 7c79850d02e535a9136ccc4cf5abea4ab4030c92 Mon Sep 17 00:00:00 2001
From: Richard Carlsson <carlsson.richard@gmail.com>
Date: Thu, 4 Feb 2021 18:15:36 +0100
Subject: [PATCH] Ensure underlining indents by code points, not bytes

---
 lib/compiler/src/sys_messages.erl | 34 +++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/lib/compiler/src/sys_messages.erl b/lib/compiler/src/sys_messages.erl
index 0b46075f81b8..e5065c8279d3 100644
--- a/lib/compiler/src/sys_messages.erl
+++ b/lib/compiler/src/sys_messages.erl
@@ -95,6 +95,10 @@ quote_source_1(File, Loc1, Line) when is_integer(Line) ->
 quote_source_1(File, {StartLine, StartCol}, {EndLine, EndCol}) ->
     case file:read_file(File) of
         {ok, Bin} ->
+            Enc = case epp:read_encoding_from_binary(Bin) of
+                      none -> epp:default_encoding();
+                      Enc0 -> Enc0
+                  end,
             Ctx =
                 if
                     StartLine =:= EndLine -> 0;
@@ -102,7 +106,7 @@ quote_source_1(File, {StartLine, StartCol}, {EndLine, EndCol}) ->
                 end,
             case seek_line(Bin, 1, StartLine - Ctx) of
                 {ok, Bin1} ->
-                    quote_source_2(Bin1, StartLine, StartCol, EndLine, EndCol, Ctx);
+                    quote_source_2(Bin1, Enc, StartLine, StartCol, EndLine, EndCol, Ctx);
                 error ->
                     ""
             end;
@@ -110,8 +114,8 @@ quote_source_1(File, {StartLine, StartCol}, {EndLine, EndCol}) ->
             ""
     end.
 
-quote_source_2(Bin, StartLine, StartCol, EndLine, EndCol, Ctx) ->
-    case take_lines(Bin, StartLine - Ctx, EndLine + Ctx) of
+quote_source_2(Bin, Enc, StartLine, StartCol, EndLine, EndCol, Ctx) ->
+    case take_lines(Bin, Enc, StartLine - Ctx, EndLine + Ctx) of
         [] ->
             "";
         Lines ->
@@ -137,7 +141,7 @@ line_prefix() ->
     "% ".
 
 fmt_line(L, Text) ->
-    io_lib:format("~ts~4.ts| ~ts\n", [line_prefix(), line_to_txt(L), Text]).
+    [line_prefix(), io_lib:format("~4.ts| ", [line_to_txt(L)]), Text, "\n"].
 
 line_to_txt(0) -> "";
 line_to_txt(L) -> integer_to_list(L).
@@ -173,9 +177,9 @@ underline(Text, Start, Start) ->
 underline(Text, Start, End) ->
     underline(Text, Start, End, 1).
 
-underline(<<$\t, Text/binary>>, Start, End, N) when N < Start ->
+underline([$\t | Text], Start, End, N) when N < Start ->
     [$\t | underline(Text, Start, End, N + 1)];
-underline(<<_, Text/binary>>, Start, End, N) when N < Start ->
+underline([_ | Text], Start, End, N) when N < Start ->
     [$\s | underline(Text, Start, End, N + 1)];
 underline(_Text, _Start, End, N) ->
     underline_1(N, End).
@@ -191,14 +195,22 @@ seek_line(<<$\r, $\n, Rest/binary>>, N, L) -> seek_line(Rest, N + 1, L);
 seek_line(<<_, Rest/binary>>, N, L) -> seek_line(Rest, N, L);
 seek_line(<<>>, _, _) -> error.
 
-take_lines(<<>>, _Here, _To) ->
+take_lines(<<>>, _Enc, _Here, _To) ->
     [];
-take_lines(Bin, Here, To) when Here =< To ->
-    {Line, Rest} = take_line(Bin, <<>>),
-    [{Here, Line} | take_lines(Rest, Here + 1, To)];
-take_lines(_Bin, _Here, _To) ->
+take_lines(Bin, Enc, Here, To) when Here =< To ->
+    {Text, Rest} = take_line(Bin, <<>>),
+    [{Here, text_to_string(Text, Enc)}
+     | take_lines(Rest, Enc, Here + 1, To)];
+take_lines(_Bin, _Enc, _Here, _To) ->
     [].
 
+text_to_string(Text, Enc) ->
+    case unicode:characters_to_list(Text, Enc) of
+        String when is_list(String) -> String;
+        {error, String, _Rest} -> String;
+        {incomplete, String, _Rest} -> String
+    end.
+
 take_line(<<$\n, Rest/binary>>, Ack) ->
     {Ack, Rest};
 take_line(<<$\r, $\n, Rest/binary>>, Ack) ->