0213 multiline string indentation

README.md

@@ -25,6 +25,19 @@ HOCON spec for reference: https://lightbend.github.io/config/
     * `key={a: 1}\n{b: 2}`
     * `key={a=1, b=2}`
 - `url()/file()/classpath()` includes are not supported
+- Quotes next to triple-quotes needs to be escaped, otherwise they are discarded.
+  Meaning `"""a""""` is parsed as `a` but not `a"`, to crrectly express `a"`, it must be one of below:
+    * Escape the last `"`: `"""a\""""`;
+    * Or add `~` around the string value: `"""~a"~"""` (see below).
+- Multiline strings allow indentation (spaces, not tabs).
+  If `~\n` (or `~\r\n`) are the only characters following the opening triple-quote, then it's a multiline string with indentation:
+    * The first line `~\n` is ignored;
+    * The indentation spaces of the following lines are trimed;
+    * Indentation is allowed but not required for empty lines;
+    * Indentation level is determined by the least number of leading spaces among the non-empty lines;
+    * Backslashes are treated as escape characters, i.e. should be escaped with another backslash;
+    * There is no need to escape quotes in multiline strings, but it's allowed;
+    * The closing triple-quote can be either `"""` or `~"""` (`~` allows the string to end with `"` without escaping).
 
 ## Schema
 

etc/unescape.conf

@@ -5,6 +5,6 @@ sql_laitin1_with_escape_1 = "SELECT * FROM \"t/1\""
 sql_laitin1_with_escape_2 = "SELECT * FROM \\\"t/1\\\""
 sql_unicode_with_escape_1 = "SELECT * FROM \"t/1\" WHERE clientid = \"-测试专用-\""
 sql_unicode_with_escape_2 = "SELECT * FROM \\\"t/1\\\" WHERE clientid = \"-测试专用-\""
-sql_unicode_with_escape_3 = "SELECT * FROM \\\"t/1\\\" WHERE clientid = \"-测试\\\n\r\t专用-\""
+sql_unicode_with_escape_3 = "SELECT * FROM \\\"t/1\\\" WHERE clientid = \"-测试\\\r\n\t专用-\""
 z = 1
 z1 = "1"

src/hocon_pp.erl

@@ -21,6 +21,7 @@
 -include("hocon_private.hrl").
 
 -define(INDENT, "  ").
+-define(TRIPLE_QUOTE, <<"\"\"\"">>).
 
 %% @doc Pretty print HOCON value.
 %% Options are:
@@ -99,10 +100,10 @@ gen(Bin, Opts) when is_binary(Bin) ->
 gen(S, Opts) when is_list(S) ->
     case io_lib:printable_latin1_list(S) of
         true ->
-            maybe_quote_latin1_str(S);
+            gen_str(S, latin1);
         false ->
             case io_lib:printable_unicode_list(S) of
-                true -> <<"\"", (format_escape_sequences(S))/binary, "\"">>;
+                true -> gen_str(S, unicode);
                 false -> gen_list(S, Opts)
             end
     end;
@@ -124,26 +125,100 @@ gen(Value, Opts) ->
         options => Opts
     }).
 
+gen_str(S, Codec) ->
+    case is_triple_quote_str(S) of
+        true ->
+            gen_triple_quote_str(S);
+        false ->
+            gen_single_quote_str(S, Codec)
+    end.
+
+%% If a string requires escaping, it is a triple quote string
+%% with one exception: if the string itself contains triple-quote
+is_triple_quote_str(Chars) ->
+    case has_triple_quotes(Chars) of
+        true ->
+            false;
+        false ->
+            lists:any(fun(C) -> esc(C) =/= C end, Chars)
+    end.
+
+%% Return 'true' if there are three consecutive quotes in a string.
+has_triple_quotes(Chars) ->
+    nomatch =/= string:find(Chars, "\"\"\"").
+
+%% If a string has '\n' in it, it's a multiline.
+%% If it has leading or trailing quotes,
+%% it's a multiline -- so that there is no need to escape the quotes.
+is_multiline([]) ->
+    false;
+is_multiline(Chars) ->
+    lists:member($\n, Chars) orelse is_leading_quote(Chars) orelse is_trailling_quote(Chars).
+
+is_leading_quote([$" | _]) -> true;
+is_leading_quote(_) -> false.
+
+is_trailling_quote(Chars) ->
+    is_leading_quote(lists:reverse(Chars)).
+
+gen_single_quote_str(S, latin1) ->
+    maybe_quote_latin1_str(S);
+gen_single_quote_str(S, unicode) ->
+    <<"\"", (format_escape_sequences(S))/binary, "\"">>.
+
+gen_triple_quote_str(Str) ->
+    [
+        ?TRIPLE_QUOTE,
+        maybe_indent(esc_backslashes(Str)),
+        ?TRIPLE_QUOTE
+    ].
+
+maybe_indent(Chars) ->
+    case is_multiline(Chars) of
+        true ->
+            ["~", indent_multiline_str(Chars), "~"];
+        false ->
+            Chars
+    end.
+
+indent_multiline_str(Chars) ->
+    Lines = hocon_scanner:split_lines(Chars),
+    indent_str_value_lines(Lines).
+
+%% mark each line for indentation with 'indent'
+%% except for empty lines in the middle of the string
+indent_str_value_lines([[]]) ->
+    %% last line being empty
+    [?NL];
+indent_str_value_lines([LastLine]) ->
+    %% last line is not empty
+    [{indent, bin(LastLine)}];
+indent_str_value_lines([[] | Lines]) ->
+    %% do not indent empty line
+    [<<"\n">> | indent_str_value_lines(Lines)];
+indent_str_value_lines([Line | Lines]) ->
+    [{indent, bin(Line)} | indent_str_value_lines(Lines)].
+
 gen_list(L, Opts) ->
     case is_oneliner(L) of
         true ->
             %% one line
             ["[", infix([gen(I, Opts) || I <- L], ", "), "]"];
         false ->
-            do_gen_list(L, Opts)
+            gen_multiline_list(L, Opts)
     end.
 
-do_gen_list([_ | _] = L, Opts) ->
+gen_multiline_list([_ | _] = L, Opts) ->
     [
-        ["[", ?NL],
-        do_gen_list_loop(L, Opts#{no_obj_nl => true}),
+        ["["],
+        gen_multiline_list_loop(L, Opts#{no_obj_nl => true}),
         ["]", ?NL]
     ].
 
-do_gen_list_loop([I], Opts) ->
+gen_multiline_list_loop([I], Opts) ->
     [{indent, gen(I, Opts)}];
-do_gen_list_loop([H | T], Opts) ->
-    [{indent, [gen(H, Opts), ","]} | do_gen_list_loop(T, Opts)].
+gen_multiline_list_loop([H | T], Opts) ->
+    [{indent, [gen(H, Opts), ","]} | gen_multiline_list_loop(T, Opts)].
 
 is_oneliner(L) when is_list(L) ->
     lists:all(fun(X) -> is_number(X) orelse is_binary(X) orelse is_atom(X) end, L);
@@ -153,7 +228,7 @@ is_oneliner(M) when is_map(M) ->
 gen_map(M, Opts) ->
     case is_oneliner(M) of
         true -> ["{", infix(gen_map_fields(M, Opts, ""), ", "), "}"];
-        false -> [["{", ?NL], {indent, gen_map_fields(M, Opts, ?NL)}, "}"]
+        false -> ["{", {indent, gen_map_fields(M, Opts, ?NL)}, [?NL, "}"]]
     end.
 
 gen_map_fields(M, Opts, NL) ->
@@ -224,7 +299,7 @@ fmt(L) when is_list(L) ->
     bin(lists:map(fun fmt/1, L));
 fmt({indent, Block}) ->
     FormattedBlock = fmt(Block),
-    bin([[?INDENT, Line, ?NL] || Line <- split(FormattedBlock)]).
+    bin([[?NL, ?INDENT, Line] || Line <- split(FormattedBlock)]).
 
 split(Bin) ->
     [Line || Line <- binary:split(Bin, ?NL, [global]), Line =/= <<>>].
@@ -256,3 +331,9 @@ esc($\") -> "\\\"";
 % \
 esc($\\) -> "\\\\";
 esc(Char) -> Char.
+
+esc_backslashes(Str) ->
+    lists:map(fun esc_backslash/1, Str).
+
+esc_backslash($\\) -> "\\\\";
+esc_backslash(Char) -> Char.

src/hocon_scanner.xrl

@@ -81,7 +81,7 @@ Rules.
 {Integer}         : {token, {integer, TokenLine, list_to_integer(TokenChars)}}.
 {Float}           : {token, {float, TokenLine, to_float(TokenChars)}}.
 {String}          : {token, {string, TokenLine, unquote(TokenChars, force_escape)}}.
-{MultilineString} : {token, {string, TokenLine, unquote(TokenChars, allow_unescaped)}}.
+{MultilineString} : {token, {string, TokenLine, unindent(unquote(TokenChars, allow_unescaped))}}.
 {Bytesize}        : {token, {string, TokenLine, TokenChars}}.
 {Percent}         : {token, {string, TokenLine, TokenChars}}.
 {Duration}        : {token, {string, TokenLine, TokenChars}}.
@@ -92,6 +92,8 @@ Rules.
 
 Erlang code.
 
+-export([split_lines/1]).
+
 maybe_include("include", TokenLine)  -> {include, TokenLine};
 maybe_include(TokenChars, TokenLine) -> {unqstr, TokenLine, TokenChars}.
 
@@ -111,6 +113,68 @@ strip_surrounded_quotes([$" | Rem]) ->
 strip_surrounded_quotes(Str) ->
     Str.
 
+unindent([$~, $\r, $\n | Chars]) ->
+    do_unindent(Chars);
+unindent([$~, $\n | Chars]) ->
+    do_unindent(Chars);
+unindent(Chars) ->
+    Chars.
+
+do_unindent(Chars) ->
+    Lines = split_lines(Chars),
+    Indent = min_indent(Lines),
+    NewLines = lists:map(fun(Line) -> trim_indents(Line, Indent) end, Lines),
+    lists:flatten(lists:join($\n, NewLines)).
+
+split_lines(Chars) ->
+    split_lines(Chars, "", []).
+
+%% Split multiline strings like
+%% """~
+%%    line1
+%%    line2
+%% ~"""
+%% into ["line1\n", "line2\n"]
+split_lines([], LastLineR, Lines) ->
+    %% if the last line ends with '-' drop it
+    LastLine = case LastLineR of
+        [$~ | Rest] ->
+            lists:reverse(Rest);
+        _ ->
+            lists:reverse(LastLineR)
+    end,
+    lists:reverse([LastLine | Lines]);
+split_lines([$\n | Chars], Line, Lines) ->
+    split_lines(Chars, [], [lists:reverse(Line) | Lines]);
+split_lines([Char | Chars], Line, Lines) ->
+    split_lines(Chars, [Char | Line], Lines).
+
+min_indent(Lines) ->
+    Indents0 = lists:map(fun indent_level/1, Lines),
+    case lists:filter(fun erlang:is_integer/1, Indents0) of
+        [] ->
+            0;
+        Indents ->
+            lists:min(Indents)
+    end.
+
+indent_level("") ->
+    ignore;
+indent_level(Line) ->
+    indent_level(Line, 0).
+
+indent_level([$\s | Chars], Count) ->
+    indent_level(Chars, Count + 1);
+indent_level(_, Count) ->
+    Count.
+
+trim_indents([], _Indent) ->
+    [];
+trim_indents(Chars, 0) ->
+    Chars;
+trim_indents([$\s | Chars], Indent) when Indent > 0 ->
+    trim_indents(Chars, Indent - 1).
+
 % the first clause is commented out on purpose
 % meaning below two escape sequence (in a hocon file)
 % key="\\""

test/hocon_pp_tests.erl

@@ -65,16 +65,6 @@ do(File) ->
     ?assertEqual(Conf, Conf3),
     file:delete(TmpFile).
 
-pp_escape_to_file_test() ->
-    File = "etc/unescape.conf",
-    {ok, Conf} = hocon:load(File),
-    PP = hocon_pp:do(Conf, #{}),
-    TmpFile = File ++ ".pp",
-    file:write_file(TmpFile, [PP]),
-    ?assertEqual(file:read_file(File), file:read_file(TmpFile)),
-    file:delete(TmpFile),
-    ok.
-
 pp_quote_test() ->
     Fun = fun(Map, ExpectBin) ->
         Bin = iolist_to_binary(hocon_pp:do(Map, #{})),
@@ -100,29 +90,48 @@ pp_quote_test() ->
     Fun(#{<<"$d_dfdk2f">> => <<"12">>}, <<"\"$d_dfdk2f\" = \"12\"\n">>),
 
     %% backslash
-    Fun(#{<<"test_backslash">> => <<"\\emqx">>}, <<"test_backslash = \"\\\\emqx\"\n">>),
-    Fun(#{<<"test_backslash">> => <<"emqx\\emqx">>}, <<"test_backslash = \"emqx\\\\emqx\"\n">>),
-    Fun(#{<<"test_backslash">> => <<"emqx\\">>}, <<"test_backslash = \"emqx\\\\\"\n">>),
+    Fun(#{<<"a">> => <<"\\emqx">>}, <<"a = \"\"\"\\\\emqx\"\"\"\n">>),
+    Fun(#{<<"b">> => <<"emqx\\emqx">>}, <<"b = \"\"\"emqx\\\\emqx\"\"\"\n">>),
+    Fun(#{<<"c">> => <<"emqx\\">>}, <<"c = \"\"\"emqx\\\\\"\"\"\n">>),
 
     %% quote
-    Fun(#{<<"test_quote">> => <<"\"emqx">>}, <<"test_quote = \"\\\"emqx\"\n">>),
-    Fun(#{<<"test_quote">> => <<"emqx\"emqx">>}, <<"test_quote = \"emqx\\\"emqx\"\n">>),
-    Fun(#{<<"test_quote">> => <<"emqx\"">>}, <<"test_quote = \"emqx\\\"\"\n">>),
+    Fun(#{<<"A">> => <<"\"emqx">>}, <<"A = \"\"\"~\n  \"emqx~\"\"\"\n">>),
+    Fun(#{<<"B">> => <<"emqx\"emqx">>}, <<"B = \"\"\"emqx\"emqx\"\"\"\n">>),
+    Fun(#{<<"C">> => <<"emqx\"">>}, <<"C = \"\"\"~\n  emqx\"~\"\"\"\n">>),
+    Fun(#{<<"D">> => <<"emqx\"\"\"">>}, <<"D = \"emqx\\\"\\\"\\\"\"\n">>),
 
     %% '${}[]:=,+#`^?!@*& ' should quote
     lists:foreach(
         fun(Char) ->
             Header = list_to_binary([Char | "emqx"]),
             Tail = list_to_binary("emqx" ++ [Char]),
             Middle = <<Tail/binary, "emqx">>,
-            Fun(#{<<"test_key">> => Header}, <<"test_key = \"", Header/binary, "\"\n">>),
-            Fun(#{<<"test_key">> => Tail}, <<"test_key = \"", Tail/binary, "\"\n">>),
-            Fun(#{<<"test_key">> => Middle}, <<"test_key = \"", Middle/binary, "\"\n">>)
+            Fun(#{<<"D">> => Header}, <<"D = \"", Header/binary, "\"\n">>),
+            Fun(#{<<"E">> => Tail}, <<"E = \"", Tail/binary, "\"\n">>),
+            Fun(#{<<"F">> => Middle}, <<"F = \"", Middle/binary, "\"\n">>)
         end,
         "'${}[]:=,+#`^?!@*& "
     ),
     ok.
 
+multi_line_str_indent_test() ->
+    Struct = #{<<"a">> => #{<<"b">> => #{<<"c">> => "line1\n\nline2\n\nline3\n"}}},
+    Expected = <<
+        "a {\n"
+        "  b {\n"
+        "    c = \"\"\"~\n"
+        "      line1\n"
+        "\n"
+        "      line2\n"
+        "\n"
+        "      line3\n"
+        "    ~\"\"\"\n"
+        "  }\n"
+        "}\n"
+    >>,
+    ?assertEqual(Expected, iolist_to_binary(hocon_pp:do(Struct, #{}))),
+    ok.
+
 load_file_pp_test() ->
     TmpF = "/tmp/load_file_pp_test",
     F = fun(Raw, Format) ->

test/hocon_tests.erl

@@ -268,8 +268,33 @@ escape_test_() ->
         )
     ].
 
-multiline_string_test_() ->
-    [].
+triple_quote_string_test_() ->
+    Parse = fun(Str) -> maps:get(<<"a">>, binary(<<"a = \"\"\"", Str/binary, "\"\"\"">>)) end,
+    [
+        ?_assertEqual(<<"1">>, Parse(<<"1">>)),
+        ?_assertEqual(<<"1">>, Parse(<<"~\n1~">>)),
+        ?_assertEqual(<<"1\n">>, Parse(<<"~\n1\n~">>)),
+        ?_assertEqual(<<"1\r\n">>, Parse(<<"~\r\n1\r\n">>)),
+        ?_assertEqual(<<"1\n\n2">>, Parse(<<"~\n1\n\n2">>)),
+        ?_assertEqual(<<"1\n\n2">>, Parse(<<"~\n    1\n\n    2">>)),
+        ?_assertEqual(<<"1\n\n2">>, Parse(<<"~\n    1\n    \n    2">>)),
+        ?_assertEqual(<<" 1\n\n2">>, Parse(<<"~\n     1\n    \n    2">>)),
+        ?_assertEqual(<<" 1\n\n2\n">>, Parse(<<"~\n     1\n    \n    2\n">>)),
+        ?_assertEqual(<<" 1\n\n2\n">>, Parse(<<"~\n     1\n    \n    2\n    ">>)),
+        ?_assertEqual(<<" 1\n\n2\n">>, Parse(<<"~\n     1\n    \n    2\n    ~">>)),
+        ?_assertEqual(<<" 1\n\n2\n ">>, Parse(<<"~\n     1\n    \n    2\n     ~">>)),
+        ?_assertEqual(<<"1\"\"\n2">>, Parse(<<"~\n     1\"\"\n     2">>)),
+        %% must escape quotes if it's next to """
+        ?_assertEqual(<<"1\"">>, Parse(<<"1\\\"">>)),
+        %% must escape quotes if it's next to """
+        ?_assertEqual(<<"\"1">>, Parse(<<"\\\"1">>)),
+        %% no need to escape quotes unless it's next to """
+        ?_assertEqual(<<"1\"2">>, Parse(<<"1\"2">>)),
+        %% empty string with closing quote in the next line
+        ?_assertEqual(<<"">>, Parse(<<"~\n">>)),
+        %% empty string with indented closing quote in the next line
+        ?_assertEqual(<<"">>, Parse(<<"~\n    ~">>))
+    ].
 
 obj_inside_array_test_() ->
     [