Allow multiple modifier characters in io:format control sequences

This makes it possible to print unicode atoms at the same time as
suppressing detection of printable lists.

2 files changed, 25 insertions, 19 deletions

diff --git a/lib/stdlib/src/erl_lint.erl b/lib/stdlib/src/erl_lint.erl
index 1930c462e8..9a62d21d34 100644
--- a/lib/stdlib/src/erl_lint.erl
+++ b/lib/stdlib/src/erl_lint.erl
@@ -3971,6 +3971,8 @@ extract_sequence(3, [$.,_|Fmt], Need) ->
     extract_sequence(4, Fmt, Need);
 extract_sequence(3, Fmt, Need) ->
     extract_sequence(4, Fmt, Need);
+extract_sequence(4, [$t, $l | Fmt], Need) ->
+    extract_sequence(4, [$l, $t | Fmt], Need);
 extract_sequence(4, [$t, $c | Fmt], Need) ->
     extract_sequence(5, [$c|Fmt], Need);
 extract_sequence(4, [$t, $s | Fmt], Need) ->
@@ -3987,8 +3989,14 @@ extract_sequence(4, [$t, C | _Fmt], _Need) ->
     {error,"invalid control ~t" ++ [C]};
 extract_sequence(4, [$l, $p | Fmt], Need) ->
     extract_sequence(5, [$p|Fmt], Need);
+extract_sequence(4, [$l, $t, $p | Fmt], Need) ->
+    extract_sequence(5, [$p|Fmt], Need);
 extract_sequence(4, [$l, $P | Fmt], Need) ->
     extract_sequence(5, [$P|Fmt], Need);
+extract_sequence(4, [$l, $t, $P | Fmt], Need) ->
+    extract_sequence(5, [$P|Fmt], Need);
+extract_sequence(4, [$l, $t, C | _Fmt], _Need) ->
+    {error,"invalid control ~lt" ++ [C]};
 extract_sequence(4, [$l, C | _Fmt], _Need) ->
     {error,"invalid control ~l" ++ [C]};
 extract_sequence(4, Fmt, Need) ->
diff --git a/lib/stdlib/src/io_lib_format.erl b/lib/stdlib/src/io_lib_format.erl
index e345810ca0..3e1f90ac24 100644
--- a/lib/stdlib/src/io_lib_format.erl
+++ b/lib/stdlib/src/io_lib_format.erl
@@ -126,25 +126,23 @@ collect_cseq(Fmt0, Args0) ->
     {F,Ad,Fmt1,Args1} = field_width(Fmt0, Args0),
     {P,Fmt2,Args2} = precision(Fmt1, Args1),
     {Pad,Fmt3,Args3} = pad_char(Fmt2, Args2),
-    {Encoding,Fmt4,Args4} = encoding(Fmt3, Args3),
-    {Strings,Fmt5,Args5} = strings(Fmt4, Args4),
-    {C,As,Fmt6,Args6} = collect_cc(Fmt5, Args5),
-    FormatSpec = #{control_char => C, args => As, width => F, adjust => Ad,
-                   precision => P, pad_char => Pad, encoding => Encoding,
-                   strings => Strings},
-    {FormatSpec,Fmt6,Args6}.
-
-encoding([$t|Fmt],Args) ->
-    true = hd(Fmt) =/= $l,
-    {unicode,Fmt,Args};
-encoding(Fmt,Args) ->
-    {latin1,Fmt,Args}.
-
-strings([$l|Fmt],Args) ->
-    true = hd(Fmt) =/= $t,
-    {false,Fmt,Args};
-strings(Fmt,Args) ->
-    {true,Fmt,Args}.
+    Spec0 = #{width => F,
+              adjust => Ad,
+              precision => P,
+              pad_char => Pad,
+              encoding => latin1,
+              strings => true},
+    {Spec1,Fmt4} = modifiers(Fmt3, Spec0),
+    {C,As,Fmt5,Args4} = collect_cc(Fmt4, Args3),
+    Spec2 = Spec1#{control_char => C, args => As},
+    {Spec2,Fmt5,Args4}.
+
+modifiers([$t|Fmt], Spec) ->
+    modifiers(Fmt, Spec#{encoding => unicode});
+modifiers([$l|Fmt], Spec) ->
+    modifiers(Fmt, Spec#{strings => false});
+modifiers(Fmt, Spec) ->
+    {Spec, Fmt}.
 
 field_width([$-|Fmt0], Args0) ->
     {F,Fmt,Args} = field_value(Fmt0, Args0),