json: Factorize the trivial implementation of `to_json`.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>

diff --git a/lib/json/static.nit b/lib/json/static.nit
index bb578fd..12dbc7c 100644 (file)
--- a/lib/json/static.nit
+++ b/lib/json/static.nit
@@ -34,12 +34,28 @@ interface Jsonable
        # SEE: `append_json`
        fun to_json: String is abstract
 
+       # Use `append_json` to implement `to_json`.
+       #
+       # Therefore, one that redefine `append_json` may use the following
+       # redefinition to link `to_json` and `append_json`:
+       #
+       # ~~~nitish
+       # redef fun to_json do return to_json_by_append
+       # ~~~
+       #
+       # Note: This is not the default implementation of `to_json` in order to
+       # avoid cyclic references between `append_json` and `to_json` when none are
+       # implemented.
+       protected fun to_json_by_append: String do
+               var buffer = new RopeBuffer
+               append_json(buffer)
+               return buffer.write_to_string
+       end
+
        # Append the JSON representation of `self` to the specified buffer.
        #
        # SEE: `to_json`
-       fun append_json(buffer: Buffer) do
-               buffer.append(to_json)
-       end
+       fun append_json(buffer: Buffer) do buffer.append(to_json)
 end
 
 redef class Text
@@ -82,11 +98,7 @@ redef class Text
        #
        #     assert "\t\"http://example.com\"\r\n\0\\".to_json ==
        #               "\"\\t\\\"http:\\/\\/example.com\\\"\\r\\n\\u0000\\\\\""
-       redef fun to_json do
-               var buffer = new FlatBuffer
-               append_json(buffer)
-               return buffer.write_to_string
-       end
+       redef fun to_json do return to_json_by_append
 
        # Parse `self` as JSON.
        #
@@ -211,11 +223,7 @@ interface JsonMapRead[K: String, V: nullable Jsonable]
        #     obj = new JsonObject
        #     obj["baz"] = null
        #     assert obj.to_json == "\{\"baz\":null\}"
-       redef fun to_json do
-               var buffer = new FlatBuffer
-               append_json(buffer)
-               return buffer.write_to_string
-       end
+       redef fun to_json do return to_json_by_append
 
        private fun append_json_entry(iterator: MapIterator[String, nullable Jsonable],
                        buffer: Buffer) do
@@ -259,11 +267,7 @@ class JsonSequenceRead[E: nullable Jsonable]
        #     assert arr.to_json =="[\"foo\"]"
        #     arr.pop
        #     assert arr.to_json =="[]"
-       redef fun to_json do
-               var buffer = new FlatBuffer
-               append_json(buffer)
-               return buffer.write_to_string
-       end
+       redef fun to_json do return to_json_by_append
 
        private fun append_json_entry(iterator: Iterator[nullable Jsonable],
                        buffer: Buffer) do