From 23e7bc085df24fd968dfd33dcecb6f288b8b0853 Mon Sep 17 00:00:00 2001
From: Andrew Thompson <andrew@hijacked.us>
Date: Thu, 10 Mar 2016 09:14:25 -0700
Subject: [PATCH] Port improper iolist support from io_lib_format.erl & add
 tests

---
 src/lager_format.erl   | 28 ++++++++++++++++++++++------
 src/lager_trunc_io.erl |  6 ++++++
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/src/lager_format.erl b/src/lager_format.erl
index d12ce3b..b4eac89 100644
--- a/src/lager_format.erl
+++ b/src/lager_format.erl
@@ -245,18 +245,34 @@ control2($P, [A,Depth], _F, _Adj, _P, _Pad, _Enc, L) when is_integer(Depth) ->
     Term = lager_trunc_io:fprint(A, L, [{depth, Depth}, {lists_as_strings, true}]),
     {Term, lists:flatlength(Term)};
 control2($s, [L0], F, Adj, P, Pad, latin1, L) ->
-    List = lager_trunc_io:fprint(maybe_flatten(L0), L, [{force_strings, true}]),
+    List = lager_trunc_io:fprint(iolist_to_chars(L0), L, [{force_strings, true}]),
     Res = string(List, F, Adj, P, Pad),
     {Res, lists:flatlength(Res)};
 control2($s, [L0], F, Adj, P, Pad, unicode, L) ->
-    List = lager_trunc_io:fprint(unicode:characters_to_list(L0), L, [{force_strings, true}]),
+    List = lager_trunc_io:fprint(cdata_to_chars(L0), L, [{force_strings, true}]),
     Res = uniconv(string(List, F, Adj, P, Pad)),
     {Res, lists:flatlength(Res)}.
 
-maybe_flatten(X) when is_list(X) ->
-    lists:flatten(X);
-maybe_flatten(X) ->
-    X.
+iolist_to_chars([C|Cs]) when is_integer(C), C >= $\000, C =< $\377 ->
+    [C | iolist_to_chars(Cs)];
+iolist_to_chars([I|Cs]) ->
+    [iolist_to_chars(I) | iolist_to_chars(Cs)];
+iolist_to_chars([]) ->
+    [];
+iolist_to_chars(B) when is_binary(B) ->
+    binary_to_list(B).
+
+cdata_to_chars([C|Cs]) when is_integer(C), C >= $\000 ->
+    [C | cdata_to_chars(Cs)];
+cdata_to_chars([I|Cs]) ->
+    [cdata_to_chars(I) | cdata_to_chars(Cs)];
+cdata_to_chars([]) ->
+    [];
+cdata_to_chars(B) when is_binary(B) ->
+    case catch unicode:characters_to_list(B) of
+        L when is_list(L) -> L;
+        _ -> binary_to_list(B)
+    end.
 
 make_options([], Options) ->
     Options;
diff --git a/src/lager_trunc_io.erl b/src/lager_trunc_io.erl
index 8763d49..7ed34c1 100644
--- a/src/lager_trunc_io.erl
+++ b/src/lager_trunc_io.erl
@@ -882,4 +882,10 @@ print_terms_without_format_string_test() ->
     ?assertError(badarg, format(65535, [], 50)),
     ok.
 
+improper_io_list_test() ->
+    ?assertEqual(">hello", lists:flatten(format('~s', [[$>|<<"hello">>]], 50))),
+    ?assertEqual(">hello", lists:flatten(format('~ts', [[$>|<<"hello">>]], 50))),
+    ?assertEqual("helloworld", lists:flatten(format('~ts', [[<<"hello">>|<<"world">>]], 50))),
+    ok.
+
 -endif.