Prototype JSON::Coder

ext/json/ext/generator/generator.c

@@ -12,6 +12,7 @@ typedef struct JSON_Generator_StateStruct {
     VALUE space_before;
     VALUE object_nl;
     VALUE array_nl;
+    VALUE as_json;
 
     long max_nesting;
     long depth;
@@ -30,8 +31,8 @@ typedef struct JSON_Generator_StateStruct {
 static VALUE mJSON, cState, mString_Extend, eGeneratorError, eNestingError, Encoding_UTF_8;
 
 static ID i_to_s, i_to_json, i_new, i_pack, i_unpack, i_create_id, i_extend, i_encode;
-static ID sym_indent, sym_space, sym_space_before, sym_object_nl, sym_array_nl, sym_max_nesting, sym_allow_nan,
-          sym_ascii_only, sym_depth, sym_buffer_initial_length, sym_script_safe, sym_escape_slash, sym_strict;
+static VALUE sym_indent, sym_space, sym_space_before, sym_object_nl, sym_array_nl, sym_max_nesting, sym_allow_nan,
+             sym_ascii_only, sym_depth, sym_buffer_initial_length, sym_script_safe, sym_escape_slash, sym_strict, sym_as_json;
 
 
 #define GET_STATE_TO(self, state) \
@@ -674,6 +675,7 @@ static void State_mark(void *ptr)
     rb_gc_mark_movable(state->space_before);
     rb_gc_mark_movable(state->object_nl);
     rb_gc_mark_movable(state->array_nl);
+    rb_gc_mark_movable(state->as_json);
 }
 
 static void State_compact(void *ptr)
@@ -684,6 +686,7 @@ static void State_compact(void *ptr)
     state->space_before = rb_gc_location(state->space_before);
     state->object_nl = rb_gc_location(state->object_nl);
     state->array_nl = rb_gc_location(state->array_nl);
+    state->as_json = rb_gc_location(state->as_json);
 }
 
 static void State_free(void *ptr)
@@ -740,6 +743,7 @@ static void vstate_spill(struct generate_json_data *data)
     RB_OBJ_WRITTEN(vstate, Qundef, state->space_before);
     RB_OBJ_WRITTEN(vstate, Qundef, state->object_nl);
     RB_OBJ_WRITTEN(vstate, Qundef, state->array_nl);
+    RB_OBJ_WRITTEN(vstate, Qundef, state->as_json);
 }
 
 static inline VALUE vstate_get(struct generate_json_data *data)
@@ -1003,6 +1007,8 @@ static void generate_json_float(FBuffer *buffer, struct generate_json_data *data
 static void generate_json(FBuffer *buffer, struct generate_json_data *data, JSON_Generator_State *state, VALUE obj)
 {
     VALUE tmp;
+    bool as_json_called = false;
+start:
     if (obj == Qnil) {
         generate_json_null(buffer, data, state, obj);
     } else if (obj == Qfalse) {
@@ -1042,7 +1048,13 @@ static void generate_json(FBuffer *buffer, struct generate_json_data *data, JSON
             default:
             general:
                 if (state->strict) {
-                    raise_generator_error(obj, "%"PRIsVALUE" not allowed in JSON", CLASS_OF(obj));
+                    if (RTEST(state->as_json) && !as_json_called) {
+                        obj = rb_proc_call_with_block(state->as_json, 1, &obj, Qnil);
+                        as_json_called = true;
+                        goto start;
+                    } else {
+                        raise_generator_error(obj, "%"PRIsVALUE" not allowed in JSON", CLASS_OF(obj));
+                    }
                 } else if (rb_respond_to(obj, i_to_json)) {
                     tmp = rb_funcall(obj, i_to_json, 1, vstate_get(data));
                     Check_Type(tmp, T_STRING);
@@ -1132,6 +1144,7 @@ static VALUE cState_init_copy(VALUE obj, VALUE orig)
     objState->space_before = origState->space_before;
     objState->object_nl = origState->object_nl;
     objState->array_nl = origState->array_nl;
+    objState->as_json = origState->as_json;
     return obj;
 }
 
@@ -1504,6 +1517,7 @@ static int configure_state_i(VALUE key, VALUE val, VALUE _arg)
     else if (key == sym_script_safe)           { state->script_safe = RTEST(val); }
     else if (key == sym_escape_slash)          { state->script_safe = RTEST(val); }
     else if (key == sym_strict)                { state->strict = RTEST(val); }
+    else if (key == sym_as_json)               { state->as_json = rb_convert_type(val, T_DATA, "Proc", "to_proc"); }
     return ST_CONTINUE;
 }
 
@@ -1682,6 +1696,7 @@ void Init_generator(void)
     sym_script_safe = ID2SYM(rb_intern("script_safe"));
     sym_escape_slash = ID2SYM(rb_intern("escape_slash"));
     sym_strict = ID2SYM(rb_intern("strict"));
+    sym_as_json = ID2SYM(rb_intern("as_json"));
 
     usascii_encindex = rb_usascii_encindex();
     utf8_encindex = rb_utf8_encindex();

lib/json/common.rb

@@ -841,6 +841,18 @@ def merge_dump_options(opts, strict: NOT_SET)
   class << self
     private :merge_dump_options
   end
+
+  class Coder
+    def initialize(options = nil, &as_json)
+      default_options = { strict: true, as_json: as_json }
+
+      @options = options ? options.merge(default_options) : default_options
+    end
+
+    def dump(object)
+      State.generate(object, @options, nil)
+    end
+  end
 end
 
 module ::Kernel

test/json/json_generator_test.rb

@@ -661,4 +661,31 @@
   def test_nonutf8_encoding
     assert_equal("\"5\u{b0}\"", "5\xb0".dup.force_encoding(Encoding::ISO_8859_1).to_json)
   end
+
+  def test_json_coder_with_proc
+    coder = JSON::Coder.new do |object|
+      "[Object object]"
+    end
+    assert_equal %(["[Object object]"]), coder.dump([Object.new])
+  end
+
+  def test_json_coder_with_proc_with_unsupported_value
+    coder = JSON::Coder.new do |object|
+      Object.new
+    end
+    assert_raise(JSON::GeneratorError) { coder.dump([Object.new]) }
+  end
+
+  def test_json_coder_options
+    coder = JSON::Coder.new(array_nl: "\n") do |object|
+      42
+    end
+
+    assert_equal "[\n42\n]", coder.dump([Object.new])
+  end
+
+  def test_json_generate_as_json_convert_to_proc
+    object = Object.new
+    assert_equal object.object_id.to_json, JSON.generate(object, strict: true, as_json: :object_id)
+  end
 end