✨ implemented an indentation character #520

An optional parameter for dump() allows to set the character to use for
indentation (default: space). In case a JSON value is serialized to an
output stream, its fill character is used (and can be set with
std::setfill).

doc/examples/dump.cpp

@@ -13,8 +13,10 @@ int main()
     std::cout << j_object.dump(-1) << "\n\n";
     std::cout << j_object.dump(0) << "\n\n";
     std::cout << j_object.dump(4) << "\n\n";
+    std::cout << j_object.dump(1, '\t') << "\n\n";
     std::cout << j_array.dump() << "\n\n";
     std::cout << j_array.dump(-1) << "\n\n";
     std::cout << j_array.dump(0) << "\n\n";
     std::cout << j_array.dump(4) << "\n\n";
+    std::cout << j_array.dump(1, '\t') << "\n\n";
 }

doc/examples/dump.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/jC8OLyTjE6EOcMZt"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/HjYnuCSOxokNvsRW"><b>online</b></a>

doc/examples/dump.output

@@ -12,6 +12,11 @@
     "two": 2
 }
 
+{
+	"one": 1,
+	"two": 2
+}
+
 [1,2,4,8,16]
 
 [1,2,4,8,16]
@@ -32,3 +37,11 @@
     16
 ]
 
+[
+	1,
+	2,
+	4,
+	8,
+	16
+]
+

doc/examples/operator_serialize.cpp

@@ -16,4 +16,5 @@ int main()
     // serialize with indentation
     std::cout << std::setw(4) << j_object << "\n\n";
     std::cout << std::setw(2) << j_array << "\n\n";
+    std::cout << std::setw(1) << std::setfill('\t') << j_object << "\n\n";
 }

doc/examples/operator_serialize.link

@@ -1 +1 @@
-<a target="_blank" href="https://wandbox.org/permlink/N3DbIOGGiGvGfSQ3"><b>online</b></a>
+<a target="_blank" href="https://wandbox.org/permlink/ibCUjqfsQiAglDVe"><b>online</b></a>

doc/examples/operator_serialize.output

@@ -15,3 +15,8 @@
   16
 ]
 
+{
+	"one": 1,
+	"two": 2
+}
+

src/json.hpp

@@ -2883,6 +2883,8 @@ class basic_json
     members will be pretty-printed with that indent level. An indent level of
     `0` will only insert newlines. `-1` (the default) selects the most compact
     representation.
+    @param[in] indent_char The character to use for indentation of @a indent is
+    greate than `0`. The default is ` ` (space).
 
     @return string containing the serialization of the JSON value
 
@@ -2893,12 +2895,12 @@ class basic_json
 
     @see https://docs.python.org/2/library/json.html#json.dump
 
-    @since version 1.0.0
+    @since version 1.0.0; indentaction character added in version 3.0.0
     */
-    string_t dump(const int indent = -1) const
+    string_t dump(const int indent = -1, const char indent_char = ' ') const
     {
         string_t result;
-        serializer s(output_adapter<char>::create(result));
+        serializer s(output_adapter<char>::create(result), indent_char);
 
         if (indent >= 0)
         {
@@ -6724,11 +6726,13 @@ class basic_json
       public:
         /*!
         @param[in] s  output stream to serialize to
+        @param[in] ichar  indentation character to use
         */
-        serializer(output_adapter_t<char> s)
+        serializer(output_adapter_t<char> s, const char ichar)
             : o(s), loc(std::localeconv()),
               thousands_sep(!loc->thousands_sep ? '\0' : loc->thousands_sep[0]),
-              decimal_point(!loc->decimal_point ? '\0' : loc->decimal_point[0])
+              decimal_point(!loc->decimal_point ? '\0' : loc->decimal_point[0]),
+              indent_char(ichar), indent_string(512, indent_char)
         {}
 
         /*!
@@ -7293,20 +7297,29 @@ class basic_json
         /// the locale's decimal point character
         const char decimal_point = '\0';
 
+        /// the indentation character
+        const char indent_char;
+
         /// the indentation string
-        string_t indent_string = string_t(512, ' ');
+        string_t indent_string;
     };
 
   public:
     /*!
     @brief serialize to stream
 
     Serialize the given JSON value @a j to the output stream @a o. The JSON
-    value will be serialized using the @ref dump member function. The
-    indentation of the output can be controlled with the member variable
-    `width` of the output stream @a o. For instance, using the manipulator
-    `std::setw(4)` on @a o sets the indentation level to `4` and the
-    serialization result is the same as calling `dump(4)`.
+    value will be serialized using the @ref dump member function.
+
+    - The indentation of the output can be controlled with the member variable
+      `width` of the output stream @a o. For instance, using the manipulator
+      `std::setw(4)` on @a o sets the indentation level to `4` and the
+      serialization result is the same as calling `dump(4)`.
+
+    - The indentation characrer can be controlled with the member variable
+      `fill` of the output stream @a o. For instance, the manipulator
+      `std::setfill('\\t')` sets indentation to use a tab character rather than
+      the default space character.
 
     @param[in,out] o  stream to serialize to
     @param[in] j  JSON value to serialize
@@ -7318,7 +7331,7 @@ class basic_json
     @liveexample{The example below shows the serialization with different
     parameters to `width` to adjust the indentation level.,operator_serialize}
 
-    @since version 1.0.0
+    @since version 1.0.0; indentaction character added in version 3.0.0
     */
     friend std::ostream& operator<<(std::ostream& o, const basic_json& j)
     {
@@ -7330,7 +7343,7 @@ class basic_json
         o.width(0);
 
         // do the actual serialization
-        serializer s(output_adapter<char>::create(o));
+        serializer s(output_adapter<char>::create(o), o.fill());
         s.dump(j, pretty_print, static_cast<unsigned int>(indentation));
         return o;
     }

test/src/unit-convenience.cpp

@@ -53,7 +53,7 @@ TEST_CASE("convenience functions")
                                       const char* escaped)
         {
             std::stringstream ss;
-            json::serializer s(json::output_adapter<char>::create(ss));
+            json::serializer s(json::output_adapter<char>::create(ss), ' ');
             s.dump_escaped(original);
             CHECK(ss.str() == escaped);
         };

test/src/unit-inspection.cpp

@@ -207,6 +207,12 @@ TEST_CASE("object inspection")
                   "{\n\"array\": [\n1,\n2,\n3,\n4\n],\n\"boolean\": false,\n\"null\": null,\n\"number\": 42,\n\"object\": {},\n\"string\": \"Hello world\"\n}");
         }
 
+        SECTION("indent=1, space='\t'")
+        {
+            CHECK(j.dump(1, '\t') ==
+                  "{\n\t\"array\": [\n\t\t1,\n\t\t2,\n\t\t3,\n\t\t4\n\t],\n\t\"boolean\": false,\n\t\"null\": null,\n\t\"number\": 42,\n\t\"object\": {},\n\t\"string\": \"Hello world\"\n}");
+        }
+
         SECTION("indent=4")
         {
             CHECK(j.dump(4) ==

test/src/unit-serialization.cpp

@@ -51,6 +51,15 @@ TEST_CASE("serialization")
             CHECK(ss.str() ==
                   "[\n    \"foo\",\n    1,\n    2,\n    3,\n    false,\n    {\n        \"one\": 1\n    }\n]");
         }
+
+        SECTION("given fill")
+        {
+            std::stringstream ss;
+            json j = {"foo", 1, 2, 3, false, {{"one", 1}}};
+            ss << std::setw(1) << std::setfill('\t') << j;
+            CHECK(ss.str() ==
+                  "[\n\t\"foo\",\n\t1,\n\t2,\n\t3,\n\tfalse,\n\t{\n\t\t\"one\": 1\n\t}\n]");
+        }
     }
 
     SECTION("operator>>")
@@ -72,5 +81,16 @@ TEST_CASE("serialization")
             CHECK(ss.str() ==
                   "[\n    \"foo\",\n    1,\n    2,\n    3,\n    false,\n    {\n        \"one\": 1\n    }\n]");
         }
+
+        SECTION("given fill")
+        {
+            std::stringstream ss;
+            json j = {"foo", 1, 2, 3, false, {{"one", 1}}};
+            ss.width(1);
+            ss.fill('\t');
+            j >> ss;
+            CHECK(ss.str() ==
+                  "[\n\t\"foo\",\n\t1,\n\t2,\n\t3,\n\tfalse,\n\t{\n\t\t\"one\": 1\n\t}\n]");
+        }
     }
 }