stdlib: Add property tests, bugfixes

- Add property tests using PropEr.
- Add new testcases to uri_string_SUITE.
- Improve calculation of parsed binary.
- Verify if input to parse() is UTF8 encoded.
- Update is_valid_map(): added check for path
  and host.

5 files changed, 566 insertions, 124 deletions

diff --git a/lib/stdlib/src/uri_string.erl b/lib/stdlib/src/uri_string.erl
index bb7079c193..893ba4c6bf 100755
--- a/lib/stdlib/src/uri_string.erl
+++ b/lib/stdlib/src/uri_string.erl
@@ -304,8 +304,6 @@ parse(URIString) when is_list(URIString) ->
 -spec recompose(URIMap) -> URIString when
       URIMap :: uri_map(),
       URIString :: uri_string().
-recompose(Map) when map_size(Map) =:= 0 ->
-    "";
 recompose(Map) ->
     case is_valid_map(Map) of
         false ->
@@ -405,7 +403,7 @@ convert_mapfields_to_list(Map) ->
 %%    URI-reference = URI / relative-ref
 %%-------------------------------------------------------------------------
 -spec parse_uri_reference(binary(), uri_map()) -> uri_map().
-parse_uri_reference(<<>>, _) -> #{};
+parse_uri_reference(<<>>, _) -> #{path => <<>>};
 parse_uri_reference(URIString, URI) ->
     try parse_scheme_start(URIString, URI) of
         Res -> Res
@@ -434,13 +432,15 @@ parse_relative_part(?STRING_REST("//", Rest), URI) ->
     %% Parse userinfo - "//" is NOT part of authority
     try parse_userinfo(Rest, URI) of
         {T, URI1} ->
-            Userinfo = calculate_parsed_part(Rest, T),
-	    URI1#{userinfo => decode_userinfo(Userinfo)}
+            Userinfo = calculate_parsed_userinfo(Rest, T),
+            URI2 = maybe_add_path(URI1),
+            URI2#{userinfo => decode_userinfo(Userinfo)}
     catch
         throw:uri_parse_error ->
             {T, URI1} = parse_host(Rest, URI),
             Host = calculate_parsed_part_sl(Rest, T),
-	    URI1#{host => decode_host(remove_brackets(Host))}
+            URI2 = maybe_add_path(URI1),
+            URI2#{host => decode_host(remove_brackets(Host))}
     end;
 parse_relative_part(?STRING_REST($/, Rest), URI) ->
     {T, URI1} = parse_segment(Rest, URI),  % path-absolute
@@ -449,11 +449,13 @@ parse_relative_part(?STRING_REST($/, Rest), URI) ->
 parse_relative_part(?STRING_REST($?, Rest), URI) ->
     {T, URI1} = parse_query(Rest, URI),  % path-empty ?query
     Query = calculate_parsed_part(Rest, T),
-    URI1#{query => decode_query(?STRING_REST($?, Query))};
+    URI2 = maybe_add_path(URI1),
+    URI2#{query => decode_query(?STRING_REST($?, Query))};
 parse_relative_part(?STRING_REST($#, Rest), URI) ->
     {T, URI1} = parse_fragment(Rest, URI),  % path-empty
-    Fragment = calculate_parsed_part(Rest, T),
-    URI1#{fragment => decode_fragment(Fragment)};
+    Fragment = calculate_parsed_fragment(Rest, T),
+    URI2 = maybe_add_path(URI1),
+    URI2#{fragment => decode_fragment(Fragment)};
 parse_relative_part(?STRING_REST(Char, Rest), URI) ->
     case is_segment_nz_nc(Char) of
         true ->
@@ -505,7 +507,7 @@ parse_segment(?STRING_REST($?, Rest), URI) ->
     {Rest, URI1#{query => decode_query(?STRING_REST($?, Query))}};
 parse_segment(?STRING_REST($#, Rest), URI) ->
     {T, URI1} = parse_fragment(Rest, URI),
-    Fragment = calculate_parsed_part(Rest, T),
+    Fragment = calculate_parsed_fragment(Rest, T),
     {Rest, URI1#{fragment => decode_fragment(Fragment)}};
 parse_segment(?STRING_REST(Char, Rest), URI) ->
     case is_pchar(Char) of
@@ -528,7 +530,7 @@ parse_segment_nz_nc(?STRING_REST($?, Rest), URI) ->
     {Rest, URI1#{query => decode_query(?STRING_REST($?, Query))}};
 parse_segment_nz_nc(?STRING_REST($#, Rest), URI) ->
     {T, URI1} = parse_fragment(Rest, URI),
-    Fragment = calculate_parsed_part(Rest, T),
+    Fragment = calculate_parsed_fragment(Rest, T),
     {Rest, URI1#{fragment => decode_fragment(Fragment)}};
 parse_segment_nz_nc(?STRING_REST(Char, Rest), URI) ->
     case is_segment_nz_nc(Char) of
@@ -566,10 +568,32 @@ parse_scheme_start(?STRING_REST(Char, Rest), URI) ->
     case is_alpha(Char) of
         true  -> {T, URI1} = parse_scheme(Rest, URI),
                  Scheme = calculate_parsed_scheme(Rest, T),
-		 URI1#{scheme => ?STRING_REST(Char, Scheme)};
+                 URI2 = maybe_add_path(URI1),
+		 URI2#{scheme => ?STRING_REST(Char, Scheme)};
         false -> throw(uri_parse_error)
     end.
 
+%% Add path component if it missing after parsing the URI.
+%% According to the URI specification there is always a
+%% path component in every URI-reference and it can be
+%% empty.
+
+%% maybe_add_path(Map) ->
+%%     case length(maps:keys(Map)) of
+%%         0 ->
+%%             Map#{path => <<>>};
+%%         _Else ->
+%%             Map
+%%     end.
+maybe_add_path(Map) ->
+    case maps:is_key(path, Map) of
+        false ->
+            Map#{path => <<>>};
+        _Else ->
+            Map
+    end.
+
+
 
 -spec parse_scheme(binary(), uri_map()) -> {binary(), uri_map()}.
 parse_scheme(?STRING_REST($:, Rest), URI) ->
@@ -603,7 +627,7 @@ parse_hier(?STRING_REST("//", Rest), URI) ->
     % Parse userinfo - "//" is NOT part of authority
     try parse_userinfo(Rest, URI) of
         {T, URI1} ->
-            Userinfo = calculate_parsed_part(Rest, T),
+            Userinfo = calculate_parsed_userinfo(Rest, T),
 	    {Rest, URI1#{userinfo => decode_userinfo(Userinfo)}}
     catch
         throw:uri_parse_error ->
@@ -621,7 +645,7 @@ parse_hier(?STRING_REST($?, Rest), URI) ->
     {Rest, URI1#{query => decode_query(?STRING_REST($?, Query))}};
 parse_hier(?STRING_REST($#, Rest), URI) ->
     {T, URI1} = parse_fragment(Rest, URI),  % path-empty
-    Fragment = calculate_parsed_part(Rest, T),
+    Fragment = calculate_parsed_fragment(Rest, T),
     {Rest, URI1#{fragment => decode_fragment(Fragment)}};
 parse_hier(?STRING_REST(Char, Rest), URI) ->  % path-rootless
     case is_pchar(Char) of
@@ -660,12 +684,11 @@ parse_hier(?STRING_EMPTY, URI) ->
 %%    userinfo    = *( unreserved / pct-encoded / sub-delims / ":" )
 %%-------------------------------------------------------------------------
 -spec parse_userinfo(binary(), uri_map()) -> {binary(), uri_map()}.
-parse_userinfo(?CHAR($@), _URI) ->
-    %% URI cannot end in userinfo state
-    throw(uri_parse_error);
+parse_userinfo(?CHAR($@), URI) ->
+    {?STRING_EMPTY, URI#{host => <<>>}};
 parse_userinfo(?STRING_REST($@, Rest), URI) ->
     {T, URI1} = parse_host(Rest, URI),
-    Host = calculate_parsed_part(Rest, T),
+    Host = calculate_parsed_host(Rest, T),
     {Rest, URI1#{host => decode_host(remove_brackets(Host))}};
 parse_userinfo(?STRING_REST(Char, Rest), URI) ->
     case is_userinfo(Char) of
@@ -726,7 +749,7 @@ is_userinfo(Char) -> is_unreserved(Char) orelse is_sub_delim(Char).
 -spec parse_host(binary(), uri_map()) -> {binary(), uri_map()}.
 parse_host(?STRING_REST($:, Rest), URI) ->
     {T, URI1} = parse_port(Rest, URI),
-    H = calculate_parsed_part(Rest, T),
+    H = calculate_parsed_port(Rest, T),
     Port = binary_to_integer(H),
     {Rest, URI1#{port => Port}};
 parse_host(?STRING_REST($/, Rest), URI) ->
@@ -741,7 +764,7 @@ parse_host(?STRING_REST($[, Rest), URI) ->
     parse_ipv6_bin(Rest, [], URI);
 parse_host(?STRING_REST($#, Rest), URI) ->
     {T, URI1} = parse_fragment(Rest, URI),  % path-empty
-    Fragment = calculate_parsed_part(Rest, T),
+    Fragment = calculate_parsed_fragment(Rest, T),
     {Rest, URI1#{fragment => decode_fragment(Fragment)}};
 parse_host(?STRING_REST(Char, Rest), URI) ->
     case is_digit(Char) of
@@ -755,7 +778,7 @@ parse_host(?STRING_EMPTY, URI) ->
 -spec parse_reg_name(binary(), uri_map()) -> {binary(), uri_map()}.
 parse_reg_name(?STRING_REST($:, Rest), URI) ->
     {T, URI1} = parse_port(Rest, URI),
-    H = calculate_parsed_part(Rest, T),
+    H = calculate_parsed_port(Rest, T),
     Port = binary_to_integer(H),
     {Rest, URI1#{port => Port}};
 parse_reg_name(?STRING_REST($/, Rest), URI) ->
@@ -768,7 +791,7 @@ parse_reg_name(?STRING_REST($?, Rest), URI) ->
     {Rest, URI1#{query => decode_query(?STRING_REST($?, Query))}};
 parse_reg_name(?STRING_REST($#, Rest), URI) ->
     {T, URI1} = parse_fragment(Rest, URI),  % path-empty
-    Fragment = calculate_parsed_part(Rest, T),
+    Fragment = calculate_parsed_fragment(Rest, T),
     {Rest, URI1#{fragment => decode_fragment(Fragment)}};
 parse_reg_name(?STRING_REST(Char, Rest), URI) ->
     case is_reg_name(Char) of
@@ -788,7 +811,7 @@ is_reg_name(Char) -> is_unreserved(Char) orelse is_sub_delim(Char).
 parse_ipv4_bin(?STRING_REST($:, Rest), Acc, URI) ->
     _ = validate_ipv4_address(lists:reverse(Acc)),
     {T, URI1} = parse_port(Rest, URI),
-    H = calculate_parsed_part(Rest, T),
+    H = calculate_parsed_port(Rest, T),
     Port = binary_to_integer(H),
     {Rest, URI1#{port => Port}};
 parse_ipv4_bin(?STRING_REST($/, Rest), Acc, URI) ->
@@ -804,7 +827,7 @@ parse_ipv4_bin(?STRING_REST($?, Rest), Acc, URI) ->
 parse_ipv4_bin(?STRING_REST($#, Rest), Acc, URI) ->
     _ = validate_ipv4_address(lists:reverse(Acc)),
     {T, URI1} = parse_fragment(Rest, URI),  % path-empty
-    Fragment = calculate_parsed_part(Rest, T),
+    Fragment = calculate_parsed_fragment(Rest, T),
     {Rest, URI1#{fragment => decode_fragment(Fragment)}};
 parse_ipv4_bin(?STRING_REST(Char, Rest), Acc, URI) ->
     case is_ipv4(Char) of
@@ -851,7 +874,7 @@ is_ipv6(Char) -> is_hex_digit(Char).
 -spec parse_ipv6_bin_end(binary(), uri_map()) -> {binary(), uri_map()}.
 parse_ipv6_bin_end(?STRING_REST($:, Rest), URI) ->
     {T, URI1} = parse_port(Rest, URI),
-    H = calculate_parsed_part(Rest, T),
+    H = calculate_parsed_port(Rest, T),
     Port = binary_to_integer(H),
     {Rest, URI1#{port => Port}};
 parse_ipv6_bin_end(?STRING_REST($/, Rest), URI) ->
@@ -864,7 +887,7 @@ parse_ipv6_bin_end(?STRING_REST($?, Rest), URI) ->
     {Rest, URI1#{query => decode_query(?STRING_REST($?, Query))}};
 parse_ipv6_bin_end(?STRING_REST($#, Rest), URI) ->
     {T, URI1} = parse_fragment(Rest, URI),  % path-empty
-    Fragment = calculate_parsed_part(Rest, T),
+    Fragment = calculate_parsed_fragment(Rest, T),
     {Rest, URI1#{fragment => decode_fragment(Fragment)}};
 parse_ipv6_bin_end(?STRING_REST(Char, Rest), URI) ->
     case is_ipv6(Char) of
@@ -902,7 +925,7 @@ parse_port(?STRING_REST($?, Rest), URI) ->
     {Rest, URI1#{query => decode_query(?STRING_REST($?, Query))}};
 parse_port(?STRING_REST($#, Rest), URI) ->
     {T, URI1} = parse_fragment(Rest, URI),  % path-empty
-    Fragment = calculate_parsed_part(Rest, T),
+    Fragment = calculate_parsed_fragment(Rest, T),
     {Rest, URI1#{fragment => decode_fragment(Fragment)}};
 parse_port(?STRING_REST(Char, Rest), URI) ->
     case is_digit(Char) of
@@ -928,7 +951,7 @@ parse_port(?STRING_EMPTY, URI) ->
 -spec parse_query(binary(), uri_map()) -> {binary(), uri_map()}.
 parse_query(?STRING_REST($#, Rest), URI) ->
     {T, URI1} = parse_fragment(Rest, URI),
-    Fragment = calculate_parsed_part(Rest, T),
+    Fragment = calculate_parsed_fragment(Rest, T),
     {Rest, URI1#{fragment => decode_fragment(Fragment)}};
 parse_query(?STRING_REST(Char, Rest), URI) ->
     case is_query(Char) of
@@ -1055,11 +1078,88 @@ remove_brackets(Addr) -> Addr.
 -spec calculate_parsed_part(binary(), binary()) -> binary().
 calculate_parsed_part(<<$?>>, _) -> <<>>;
 calculate_parsed_part(<<$#>>, _) -> <<>>;
+calculate_parsed_part(<<>>, _) -> <<>>;
+calculate_parsed_part(Input, <<>>) ->
+    case binary:last(Input) of
+        $? ->
+            init_binary(Input);
+        $# ->
+            init_binary(Input);
+        _Else ->
+            Input
+    end;
 calculate_parsed_part(Input, Unparsed) ->
     {First, _} = split_binary(Input, byte_size(Input) - byte_size_exl_head(Unparsed)),
     First.
 
 
+-spec calculate_parsed_userinfo(binary(), binary()) -> binary().
+calculate_parsed_userinfo(<<$?>>, _) -> <<>>;
+calculate_parsed_userinfo(<<$#>>, _) -> <<>>;
+calculate_parsed_userinfo(<<>>, _) -> <<>>;
+calculate_parsed_userinfo(Input, <<>>) ->
+    case binary:last(Input) of
+        $? ->
+            init_binary(Input);
+        $# ->
+            init_binary(Input);
+        $@ ->
+            init_binary(Input);
+        _Else ->
+            Input
+    end;
+calculate_parsed_userinfo(Input, Unparsed) ->
+    {First, _} = split_binary(Input, byte_size(Input) - byte_size_exl_head(Unparsed)),
+    First.
+
+
+-spec calculate_parsed_host(binary(), binary()) -> binary().
+calculate_parsed_host(<<$?>>, _) -> <<>>;
+calculate_parsed_host(<<$#>>, _) -> <<>>;
+calculate_parsed_host(<<>>, _) -> <<>>;
+calculate_parsed_host(Input, <<>>) ->
+    case binary:last(Input) of
+        $? ->
+            init_binary(Input);
+        $# ->
+            init_binary(Input);
+        $/ ->
+            init_binary(Input);
+        _Else ->
+            Input
+    end;
+calculate_parsed_host(Input, Unparsed) ->
+    {First, _} = split_binary(Input, byte_size(Input) - byte_size_exl_head(Unparsed)),
+    First.
+
+
+-spec calculate_parsed_port(binary(), binary()) -> binary().
+calculate_parsed_port(<<$?>>, _) -> <<>>;
+calculate_parsed_port(<<$#>>, _) -> <<>>;
+calculate_parsed_port(<<>>, _) -> <<>>;
+calculate_parsed_port(Input, <<>>) ->
+    case binary:last(Input) of
+        $? ->
+            init_binary(Input);
+        $# ->
+            init_binary(Input);
+        $/ ->
+            init_binary(Input);
+        _Else ->
+            Input
+    end;
+calculate_parsed_port(Input, Unparsed) ->
+    {First, _} = split_binary(Input, byte_size(Input) - byte_size_exl_head(Unparsed)),
+    First.
+
+
+-spec calculate_parsed_fragment(binary(), binary()) -> binary().
+calculate_parsed_fragment(<<$#>>, _) -> <<>>;
+calculate_parsed_fragment(Input, Unparsed) ->
+    {First, _} = split_binary(Input, byte_size(Input) - byte_size_exl_head(Unparsed)),
+    First.
+
+
 %% Returns the parsed binary based on Input and the Unparsed part.
 %% Used when parsing authority.
 %%
@@ -1079,28 +1179,25 @@ calculate_parsed_part_sl(<<>>, _) -> <<>>;
 calculate_parsed_part_sl(Input, <<>>) ->
     case binary:last(Input) of
         $? ->
-            {First, _} =
-                split_binary(Input, byte_size(Input) - 1),
-            First;
-
+            init_binary(Input);
         $# ->
-            {First, _} =
-                split_binary(Input, byte_size(Input) - 1),
-            First;
+            init_binary(Input);
         $/ ->
-            {First, _} =
-                split_binary(Input, byte_size(Input) - 1),
-            First;
+            init_binary(Input);
         _Else ->
-            {First, _} =
-                split_binary(Input, byte_size_exl_single_slash(Input)),
-            First
+            Input
     end;
 calculate_parsed_part_sl(Input, Unparsed) ->
     {First, _} =
         split_binary(Input, byte_size_exl_single_slash(Input) - byte_size_exl_head(Unparsed)),
     First.
 
+%% Return all bytes of the binary except the last one. The binary must be non-empty.
+init_binary(B) ->
+    {Init, _} =
+        split_binary(B, byte_size(B) - 1),
+    Init.
+
 
 %% Returns the parsed binary based on Input and the Unparsed part.
 %% Used when parsing scheme.
@@ -1109,6 +1206,7 @@ calculate_parsed_scheme(Input, Unparsed) ->
     {First, _} = split_binary(Input, byte_size(Input) - byte_size(Unparsed) - 1),
     First.
 
+
 %% Returns the size of a binary exluding the first element.
 %% Used in calls to split_binary().
 -spec byte_size_exl_head(binary()) -> number().
@@ -1149,25 +1247,35 @@ byte_size_exl_single_slash(Rest) -> byte_size(Rest).
 %%-------------------------------------------------------------------------
 -spec decode_userinfo(binary()) -> binary().
 decode_userinfo(Cs) ->
-    decode(Cs, fun is_userinfo/1, <<>>).
+    check_utf8(decode(Cs, fun is_userinfo/1, <<>>)).
 
 -spec decode_host(binary()) -> binary().
 decode_host(Cs) ->
-    decode(Cs, fun is_host/1, <<>>).
+    check_utf8(decode(Cs, fun is_host/1, <<>>)).
 
 -spec decode_path(binary()) -> binary().
 decode_path(Cs) ->
-    decode(Cs, fun is_path/1, <<>>).
+    check_utf8(decode(Cs, fun is_path/1, <<>>)).
 
 -spec decode_query(binary()) -> binary().
 decode_query(Cs) ->
-    decode(Cs, fun is_query/1, <<>>).
+    check_utf8(decode(Cs, fun is_query/1, <<>>)).
 
 -spec decode_fragment(binary()) -> binary().
 decode_fragment(Cs) ->
-    decode(Cs, fun is_fragment/1, <<>>).
+    check_utf8(decode(Cs, fun is_fragment/1, <<>>)).
 
 
+%% Returns Cs if it is utf8 encoded.
+check_utf8(Cs) ->
+    case unicode:characters_to_list(Cs) of
+        {incomplete,_,_} ->
+            throw(uri_parse_error);
+        {error,_,_} ->
+            throw(uri_parse_error);
+        _ -> Cs
+    end.
+
 %%-------------------------------------------------------------------------
 %% Percent-encode
 %%-------------------------------------------------------------------------
@@ -1368,10 +1476,15 @@ bracket_ipv6(Addr) when is_list(Addr) ->
 %%     E.g. "//user@:8080" => #{host => [],port => 8080,userinfo => "user"}
 %%     There is always at least an empty host when both userinfo and port
 %%     are present.
+%%   - #{path => "///"} otherwise the following would be true:
+%%     "/////" = uri_string:recompose(#{host => "", path => "///"})
+%%     "/////" = uri_string:recompose(#{path => "/////"})
+%%     AND
+%%     path-absolute = "/" [ segment-nz *( "/" segment ) ]
 %%-------------------------------------------------------------------------
 is_valid_map(Map) ->
     case
-        (not maps:is_key(userinfo, Map) andalso
+        ((not maps:is_key(userinfo, Map) andalso
          not maps:is_key(host, Map) andalso
          maps:is_key(port, Map))
         orelse
@@ -1381,7 +1494,9 @@ is_valid_map(Map) ->
         orelse
         (maps:is_key(userinfo, Map) andalso
          not maps:is_key(host, Map) andalso
-         maps:is_key(port, Map))
+         maps:is_key(port, Map))) orelse
+        not maps:is_key(path, Map) orelse
+        not is_host_and_path_valid(Map)
     of
         true ->
             false;
@@ -1390,6 +1505,19 @@ is_valid_map(Map) ->
     end.
 
 
+is_host_and_path_valid(Map) ->
+    Host = maps:get(host, Map, undefined),
+    Path = maps:get(path, Map, undefined),
+    not (Host =:= undefined andalso starts_with_two_slash(Path)).
+
+
+starts_with_two_slash([$/,$/|_]) ->
+    true;
+starts_with_two_slash(?STRING_REST("//", _)) ->
+    true;
+starts_with_two_slash(_) -> false.
+
+
 update_scheme(#{scheme := Scheme}, _) ->
     add_colon_postfix(encode_scheme(Scheme));
 update_scheme(#{}, _) ->
diff --git a/lib/stdlib/test/property_test/uri_string_decode.erl b/lib/stdlib/test/property_test/uri_string_decode.erl
deleted file mode 100644
index 137a649cf1..0000000000
--- a/lib/stdlib/test/property_test/uri_string_decode.erl
+++ /dev/null
@@ -1,55 +0,0 @@
-%%
-%% %CopyrightBegin%
-%%
-%% Copyright Ericsson AB 2008-2017. All Rights Reserved.
-%%
-%% Licensed under the Apache License, Version 2.0 (the "License");
-%% you may not use this file except in compliance with the License.
-%% You may obtain a copy of the License at
-%%
-%%     http://www.apache.org/licenses/LICENSE-2.0
-%%
-%% Unless required by applicable law or agreed to in writing, software
-%% distributed under the License is distributed on an "AS IS" BASIS,
-%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-%% See the License for the specific language governing permissions and
-%% limitations under the License.
-%%
-%% %CopyrightEnd%
-%%
--module(uri_string_decode).
-
--compile(export_all).
-
--proptest(eqc).
--proptest([triq,proper]).
-
--ifndef(EQC).
--ifndef(PROPER).
--ifndef(TRIQ).
--define(EQC,true).
--endif.
--endif.
--endif.
-
--ifdef(EQC).
--include_lib("eqc/include/eqc.hrl").
--define(MOD_eqc,eqc).
-
--else.
--ifdef(PROPER).
--include_lib("proper/include/proper.hrl").
--define(MOD_eqc,proper).
-
--else.
--ifdef(TRIQ).
--define(MOD_eqc,triq).
--include_lib("triq/include/triq.hrl").
-
--endif.
--endif.
--endif.
-
-
-prop_uri_string_decode() ->
-    ok.
diff --git a/lib/stdlib/test/property_test/uri_string_recompose.erl b/lib/stdlib/test/property_test/uri_string_recompose.erl
new file mode 100644
index 0000000000..dad67cd4c1
--- /dev/null
+++ b/lib/stdlib/test/property_test/uri_string_recompose.erl
@@ -0,0 +1,360 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2008-2017. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%%     http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(uri_string_recompose).
+
+-compile(export_all).
+
+-proptest(eqc).
+-proptest([triq,proper]).
+
+-ifndef(EQC).
+-ifndef(PROPER).
+-ifndef(TRIQ).
+-define(EQC,true).
+-endif.
+-endif.
+-endif.
+
+-ifdef(EQC).
+-include_lib("eqc/include/eqc.hrl").
+-define(MOD_eqc,eqc).
+
+-else.
+-ifdef(PROPER).
+-include_lib("proper/include/proper.hrl").
+-define(MOD_eqc,proper).
+
+-else.
+-ifdef(TRIQ).
+-define(MOD_eqc,triq).
+-include_lib("triq/include/triq.hrl").
+
+-endif.
+-endif.
+-endif.
+
+
+-define(STRING_REST(MatchStr, Rest), <<MatchStr/utf8, Rest/binary>>).
+
+-define(SCHEME, {scheme, scheme()}).
+-define(USER, {userinfo, unicode()}).
+-define(HOST, {host, host_map()}).
+-define(PORT, {port, port()}).
+-define(PATH_ABE, {path, path_abempty_map()}).
+-define(PATH_ABS, {path, path_absolute_map()}).
+-define(PATH_NOS, {path, path_noscheme_map()}).
+-define(PATH_ROO, {path, path_rootless_map()}).
+-define(PATH_EMP, {path, path_empty_map()}).
+-define(QUERY, {query, query_map()}).
+-define(FRAGMENT, {fragment, fragment_map()}).
+
+
+%%%========================================================================
+%%% Properties
+%%%========================================================================
+
+prop_recompose() ->
+    ?FORALL(Map, map(),
+            Map =:= uri_string:parse(uri_string:recompose(Map))
+           ).
+
+%% Stats
+prop_map_key_length_collect() ->
+    ?FORALL(List, map(),
+            collect(length(maps:keys(List)), true)).
+
+prop_map_collect() ->
+    ?FORALL(List, map(),
+            collect(lists:sort(maps:keys(List)), true)).
+
+prop_scheme_collect() ->
+    ?FORALL(List, scheme(),
+            collect(length(List), true)).
+
+
+%%%========================================================================
+%%% Generators
+%%%========================================================================
+
+map() ->
+    ?LET(Gen, comp_proplist(), proplist_to_map(Gen)).
+
+comp_proplist() ->
+    frequency([
+               {2, [?SCHEME,?PATH_ABS]},
+               {2, [?SCHEME,?PATH_ROO]},
+               {2, [?SCHEME,?PATH_EMP]},
+               {2, [?SCHEME,?HOST,?PATH_ABE]},
+               {2, [?SCHEME,?USER,?HOST,?PATH_ABE]},
+               {2, [?SCHEME,?HOST,?PORT,?PATH_ABE]},
+               {2, [?SCHEME,?USER,?HOST,?PORT,?PATH_ABE]},
+
+               {2, [?PATH_ABS]},
+               {2, [?PATH_NOS]},
+               {2, [?PATH_EMP]},
+               {2, [?HOST,?PATH_ABE]},
+               {2, [?USER,?HOST,?PATH_ABE]},
+               {2, [?HOST,?PORT,?PATH_ABE]},
+               {2, [?USER,?HOST,?PORT,?PATH_ABE]},
+
+
+               {2, [?SCHEME,?PATH_ABS,?QUERY]},
+               {2, [?SCHEME,?PATH_ROO,?QUERY]},
+               {2, [?SCHEME,?PATH_EMP,?QUERY]},
+               {2, [?SCHEME,?HOST,?PATH_ABE,?QUERY]},
+               {2, [?SCHEME,?USER,?HOST,?PATH_ABE,?QUERY]},
+               {2, [?SCHEME,?HOST,?PORT,?PATH_ABE,?QUERY]},
+               {2, [?SCHEME,?USER,?HOST,?PORT,?PATH_ABE,?QUERY]},
+
+               {2, [?PATH_ABS,?QUERY]},
+               {2, [?PATH_NOS,?QUERY]},
+               {2, [?PATH_EMP,?QUERY]},
+               {2, [?HOST,?PATH_ABE,?QUERY]},
+               {2, [?USER,?HOST,?PATH_ABE,?QUERY]},
+               {2, [?HOST,?PORT,?PATH_ABE,?QUERY]},
+               {2, [?USER,?HOST,?PORT,?PATH_ABE,?QUERY]},
+
+
+               {2, [?SCHEME,?PATH_ABS,?FRAGMENT]},
+               {2, [?SCHEME,?PATH_ROO,?FRAGMENT]},
+               {2, [?SCHEME,?PATH_EMP,?FRAGMENT]},
+               {2, [?SCHEME,?HOST,?PATH_ABE,?FRAGMENT]},
+               {2, [?SCHEME,?USER,?HOST,?PATH_ABE,?FRAGMENT]},
+               {2, [?SCHEME,?HOST,?PORT,?PATH_ABE,?FRAGMENT]},
+               {2, [?SCHEME,?USER,?HOST,?PORT,?PATH_ABE,?FRAGMENT]},
+
+               {2, [?PATH_ABS,?FRAGMENT]},
+               {2, [?PATH_NOS,?FRAGMENT]},
+               {2, [?PATH_EMP,?FRAGMENT]},
+               {2, [?HOST,?PATH_ABE,?FRAGMENT]},
+               {2, [?USER,?HOST,?PATH_ABE,?FRAGMENT]},
+               {2, [?HOST,?PORT,?PATH_ABE,?FRAGMENT]},
+               {2, [?USER,?HOST,?PORT,?PATH_ABE,?FRAGMENT]},
+
+
+               {2, [?SCHEME,?PATH_ABS,?QUERY,?FRAGMENT]},
+               {2, [?SCHEME,?PATH_ROO,?QUERY,?FRAGMENT]},
+               {2, [?SCHEME,?PATH_EMP,?QUERY,?FRAGMENT]},
+               {2, [?SCHEME,?HOST,?PATH_ABE,?QUERY,?FRAGMENT]},
+               {2, [?SCHEME,?USER,?HOST,?PATH_ABE,?QUERY,?FRAGMENT]},
+               {2, [?SCHEME,?HOST,?PORT,?PATH_ABE,?QUERY,?FRAGMENT]},
+               {2, [?SCHEME,?USER,?HOST,?PORT,?PATH_ABE,?QUERY,?FRAGMENT]},
+
+               {2, [?PATH_ABS,?QUERY,?FRAGMENT]},
+               {2, [?PATH_NOS,?QUERY,?FRAGMENT]},
+               {2, [?PATH_EMP,?QUERY,?FRAGMENT]},
+               {2, [?HOST,?PATH_ABE,?QUERY,?FRAGMENT]},
+               {2, [?USER,?HOST,?PATH_ABE,?QUERY,?FRAGMENT]},
+               {2, [?HOST,?PORT,?PATH_ABE,?QUERY,?FRAGMENT]},
+               {2, [?USER,?HOST,?PORT,?PATH_ABE,?QUERY,?FRAGMENT]}
+              ]).
+
+
+%%-------------------------------------------------------------------------
+%% Path
+%%-------------------------------------------------------------------------
+path_abempty_map() ->
+    frequency([{90, path_abe_map()},
+               {10, path_empty_map()}]).
+
+path_abe_map() ->
+    ?SIZED(Length, path_abe_map(Length, [])).
+%%
+path_abe_map(0, Segments) ->
+    ?LET(Gen, Segments, lists:append(Gen));
+path_abe_map(N, Segments) ->
+    path_abe_map(N-1, [slash(),segment()|Segments]).
+
+
+path_absolute_map() ->
+    ?SIZED(Length, path_absolute_map(Length, [])).
+%%
+path_absolute_map(0, Segments) ->
+    ?LET(Gen, [slash(),segment_nz()|Segments], lists:append(Gen));
+path_absolute_map(N, Segments) ->
+    path_absolute_map(N-1, [slash(),segment()|Segments]).
+
+
+path_noscheme_map() ->
+    ?SIZED(Length, path_noscheme_map(Length, [])).
+%%
+path_noscheme_map(0, Segments) ->
+    ?LET(Gen, [segment_nz_nc()|Segments], lists:append(Gen));
+path_noscheme_map(N, Segments) ->
+    path_noscheme_map(N-1, [slash(),segment()|Segments]).
+
+path_rootless_map() ->
+    ?SIZED(Length, path_rootless_map(Length, [])).
+%%
+path_rootless_map(0, Segments) ->
+    ?LET(Gen, [segment_nz()|Segments], lists:append(Gen));
+path_rootless_map(N, Segments) ->
+    path_rootless_map(N-1, [slash(),segment()|Segments]).
+
+
+segment_nz() ->
+    non_empty(segment()).
+
+segment_nz_nc() ->
+    non_empty(list(frequency([{30, unreserved()},
+                              {10, sub_delims()},
+                              {10, unicode_char()},
+                              {5, oneof([$@])}
+                             ]))).
+
+
+segment() ->
+    list(frequency([{30, unreserved()},
+                    {10, sub_delims()},
+                    {10, unicode_char()},
+                    {5, oneof([$:, $@])}
+                   ])).
+
+slash() ->
+    "/".
+
+path_empty_map() ->
+    "".
+
+
+%%-------------------------------------------------------------------------
+%% Path
+%%-------------------------------------------------------------------------
+host_map() ->
+    frequency([{30, reg_name()},
+               {30, ip_address()}
+              ]).
+
+
+reg_name() ->
+    list(frequency([{30, alpha()},
+                              {10, sub_delims()},
+                              {10, unicode_char()}
+                             ])).
+
+ip_address() ->
+    oneof(["127.0.0.1", "::127.0.0.1",
+           "2001:0db8:0000:0000:0000:0000:1428:07ab",
+           "2001:0db8:0000:0000:0000::1428:07ab",
+           "2001:0db8:0:0:0:0:1428:07ab",
+           "2001:0db8:0::0:1428:07ab"]).
+
+%% Generating only reg-names
+host_uri() ->
+    non_empty(list(frequency([{30, unreserved()},
+                              {10, sub_delims()},
+                              {10, pct_encoded()}
+                             ]))).
+
+%%-------------------------------------------------------------------------
+%% Port, Query, Fragment
+%%-------------------------------------------------------------------------
+port() ->
+    range(1,65535).
+
+
+query_map() ->
+    [$?| unicode()].
+
+
+query_uri() ->
+    [$?| non_empty(list(frequency([{20, pchar()},
+                                   {5, oneof([$/, $?])} % punctuation
+                                  ])))].
+
+fragment_map() ->
+    unicode().
+
+fragment_uri() ->
+    [$?| non_empty(list(frequency([{20, pchar()},
+                                   {5, oneof([$/, $?])} % punctuation
+                                  ])))].
+
+
+%%-------------------------------------------------------------------------
+%% Scheme
+%%-------------------------------------------------------------------------
+scheme() ->
+    ?SIZED(Length, scheme_start(Length, [])).
+%%
+scheme_start(0, L) ->
+    ?LET(Gen, L, lists:reverse(Gen));
+scheme_start(N, L) ->
+    scheme(N-1,[alpha()|L]).
+
+scheme(0, L) ->
+    ?LET(Gen, L, lists:reverse(Gen));
+scheme(N, L) ->
+    scheme(N-1, [scheme_char()|L]).
+
+
+%%-------------------------------------------------------------------------
+%% Misc
+%%-------------------------------------------------------------------------
+unicode() ->
+    list(frequency([{20, alpha()},                    % alpha
+               {10, digit()},                    % digit
+               {10, unicode_char()}              % unicode
+              ])).
+
+scheme_char() ->
+    frequency([{20, alpha()},                    % alpha
+               {20, digit()},                    % digit
+               {5, oneof([$+, $-, $.])}          % punctuation
+              ]).
+
+sub_delims() ->
+    oneof([$!, $$, $&, $', $(, $),
+           $*, $+, $,,$;, $=]).
+
+pchar() ->
+    frequency([{20, unreserved()},
+               {5, pct_encoded()},
+               {5, sub_delims()},
+               {1, oneof([$:, $@])}              % punctuation
+              ]).
+
+unreserved() ->
+    frequency([{20, alpha()},
+               {5, digit()},
+               {1, oneof([$-, $., $_, $~])}      % punctuation
+              ]).
+
+unicode_char() ->
+    range(913, 1023).
+
+alpha() ->
+    frequency([{20, range($a, $z)},              % letters
+               {20, range($A, $Z)}]).            % letters
+
+digit() ->
+    range($0, $9).                               % numbers
+
+pct_encoded() ->
+    oneof(["%C3%A4", "%C3%A5", "%C3%B6"]).
+
+
+%%%========================================================================
+%%% Helpers
+%%%========================================================================
+proplist_to_map(L) ->
+    lists:foldl(fun({K,V},M) -> M#{K => V};
+                  (_,M) -> M
+               end, #{}, L).
diff --git a/lib/stdlib/test/uri_string_SUITE.erl b/lib/stdlib/test/uri_string_SUITE.erl
index 0eb5105c35..cd2e003d02 100644
--- a/lib/stdlib/test/uri_string_SUITE.erl
+++ b/lib/stdlib/test/uri_string_SUITE.erl
@@ -31,7 +31,8 @@
          parse_path/1, parse_pct_encoded_fragment/1, parse_pct_encoded_query/1,
          parse_pct_encoded_userinfo/1, parse_port/1,
          parse_query/1, parse_scheme/1, parse_userinfo/1,
-	 parse_list/1, parse_binary/1, parse_mixed/1, parse_relative/1, parse_special/1,
+	 parse_list/1, parse_binary/1, parse_mixed/1, parse_relative/1,
+         parse_special/1, parse_special2/1,
          recompose_fragment/1, recompose_parse_fragment/1,
          recompose_query/1, recompose_parse_query/1,
          recompose_path/1, recompose_parse_path/1,
@@ -90,6 +91,7 @@ all() ->
      parse_mixed,
      parse_relative,
      parse_special,
+     parse_special2,
      recompose_fragment,
      recompose_parse_fragment,
      recompose_query,
@@ -114,7 +116,7 @@ uri_combinations() ->
         Hst <- [fun update_host/1, fun update_host_binary/1,
                 fun update_ipv6/1, fun update_ipv6_binary/1, none],
         Prt <- [fun update_port/1, none],
-        Pat <- [fun update_path/1, fun update_path_binary/1, none],
+        Pat <- [fun update_path/1, fun update_path_binary/1],
         Qry <- [fun update_query/1,fun update_query_binary/1, none],
         Frg <- [fun update_fragment/1, fun update_fragment_binary/1, none],
         not (Usr =:= none andalso Hst =:= none andalso Prt =/= none),
@@ -312,9 +314,7 @@ parse_binary_userinfo(_Config) ->
     #{scheme := <<"foo">>, userinfo := <<"user">>, host := <<"localhost">>} =
         uri_string:parse(<<"foo://user@localhost">>),
     #{scheme := <<"foo">>, userinfo := <<"user:password">>, host := <<"localhost">>} =
-        uri_string:parse(<<"foo://user:password@localhost">>),
-    uri_parse_error =(catch uri_string:parse(<<"//user@">>)),
-    uri_parse_error = (catch uri_string:parse(<<"foo://user@">>)).
+        uri_string:parse(<<"foo://user:password@localhost">>).
 
 parse_binary_pct_encoded_userinfo(_Config) ->
     #{scheme := <<"user">>, path := <<"合@気道"/utf8>>} =
@@ -667,14 +667,24 @@ parse_special(_Config) ->
     #{host := "foo",path := "/"} = uri_string:parse("//foo/"),
     #{host := "foo",query := "?",scheme := "http"} = uri_string:parse("http://foo?"),
     #{fragment := [],host := "foo",scheme := "http"} = uri_string:parse("http://foo#"),
-    #{host := "foo",path := "/",scheme := "http"} = uri_string:parse("http://foo/").
+    #{host := "foo",path := "/",scheme := "http"} = uri_string:parse("http://foo/"),
+    #{fragment := [],host := "host",port := 80,scheme := "http"} = uri_string:parse("http://host:80#"),
+    #{host := "host",port := 80,query := "?",scheme := "http"} = uri_string:parse("http://host:80?").
+
+parse_special2(_Config) ->
+    #{host := [],path := "/",port := 1,scheme := "a"} = uri_string:parse("a://:1/"),
+    #{path := "/a/",scheme := "a"} = uri_string:parse("a:/a/"),
+    #{host := [],path := [],userinfo := []} = uri_string:parse("//@"),
+    #{host := [],path := [],scheme := "foo",userinfo := []} = uri_string:parse("foo://@"),
+    #{host := [],path := "/",userinfo := []} = uri_string:parse("//@/"),
+    #{host := [],path := "/",scheme := "foo",userinfo := []} = uri_string:parse("foo://@/").
 
 %%-------------------------------------------------------------------------
 %% Recompose tests
 %%-------------------------------------------------------------------------
 recompose_fragment(_Config) ->
-    <<?FRAGMENT_ENC>> = uri_string:recompose(#{fragment => <<?FRAGMENT/utf8>>}),
-    ?FRAGMENT_ENC = uri_string:recompose(#{fragment => ?FRAGMENT}).
+    <<?FRAGMENT_ENC>> = uri_string:recompose(#{fragment => <<?FRAGMENT/utf8>>, path => <<>>}),
+    ?FRAGMENT_ENC = uri_string:recompose(#{fragment => ?FRAGMENT, path => ""}).
 
 recompose_parse_fragment(_Config) ->
     <<?FRAGMENT_ENC>> = uri_string:recompose(uri_string:parse(<<?FRAGMENT_ENC>>)),
@@ -682,15 +692,17 @@ recompose_parse_fragment(_Config) ->
 
 recompose_query(_Config) ->
     <<?QUERY_ENC>> =
-        uri_string:recompose(#{query => <<?QUERY/utf8>>}),
+        uri_string:recompose(#{query => <<?QUERY/utf8>>, path => <<>>}),
     <<?QUERY_ENC?FRAGMENT_ENC>> =
         uri_string:recompose(#{query => <<?QUERY/utf8>>,
-                               fragment => <<?FRAGMENT/utf8>>}),
+                               fragment => <<?FRAGMENT/utf8>>,
+                               path => <<>>}),
     "?name=%C3%B6rn" =
-        uri_string:recompose(#{query => "?name=örn"}),
+        uri_string:recompose(#{query => "?name=örn", path => ""}),
     "?name=%C3%B6rn#n%C3%A4sa" =
         uri_string:recompose(#{query => "?name=örn",
-                               fragment => "näsa"}).
+                               fragment => "näsa",
+                               path => ""}).
 
 recompose_parse_query(_Config) ->
     <<"?name=%C3%B6rn">> = uri_string:recompose(uri_string:parse(<<"?name=%C3%B6rn">>)),
diff --git a/lib/stdlib/test/uri_string_property_test_SUITE.erl b/lib/stdlib/test/uri_string_property_test_SUITE.erl
index de5edf54aa..ae2c61c7aa 100644
--- a/lib/stdlib/test/uri_string_property_test_SUITE.erl
+++ b/lib/stdlib/test/uri_string_property_test_SUITE.erl
@@ -20,10 +20,9 @@
 -module(uri_string_property_test_SUITE).
 
 -include_lib("common_test/include/ct.hrl").
-
 -compile(export_all).
 
-all() -> [decode].
+all() -> [recompose].
 
 init_per_suite(Config) ->
     ct_property_test:init_per_suite(Config).
@@ -31,12 +30,10 @@ init_per_suite(Config) ->
 end_per_suite(Config) ->
     Config.
 
-%%%================================================================
+%%%========================================================================
 %%% Test suites
-%%%
-
-decode(Config) ->
+%%%========================================================================
+recompose(Config) ->
     ct_property_test:quickcheck(
-      uri_string_decode:prop_uri_string_decode(),
-      Config
-     ).
+      uri_string_recompose:prop_recompose(),
+      Config).