Enable optional object/array members in json_pack()

doc/apiref.rst

@@ -1269,6 +1269,14 @@ arguments.
 
  .. versionadded:: 2.8
 
+``s*`` (string) [const char \*]
+ Like ``s``, but if the argument is *NULL*, do not output any value.
+ This format can only be used inside an object or an array. If used
+ inside an object, the corresponding key is additionally suppressed
+ when the value is omitted. See below for an example.
+
+ .. versionadded:: 2.11
+
 ``s#`` (string) [const char \*, int]
  Convert a UTF-8 buffer of a given length to a JSON string.
 
@@ -1324,11 +1332,20 @@ arguments.
  yourself.
 
 ``o?``, ``O?`` (any value) [json_t \*]
- Like ``o`` and ``O?``, respectively, but if the argument is
+ Like ``o`` and ``O``, respectively, but if the argument is
  *NULL*, output a JSON null value.
 
  .. versionadded:: 2.8
 
+``o*``, ``O*`` (any value) [json_t \*]
+ Like ``o`` and ``O``, respectively, but if the argument is
+ *NULL*, do not output any value. This format can only be used
+ inside an object or an array. If used inside an object, the
+ corresponding key is additionally suppressed. See below for an
+ example.
+
+ .. versionadded:: 2.11
+
 ``[fmt]`` (array)
  Build an array with contents from the inner format string. ``fmt``
  may contain objects and arrays, i.e. recursive value building is
@@ -1387,6 +1404,10 @@ More examples::
  /* Concatenate strings together to build the JSON string "foobarbaz" */
  json_pack("s++", "foo", "bar", "baz");
 
+ /* Create an empty object or array when optional members are missing */
+ json_pack("{s:s*,s:o*,s:O*}", "foo", NULL, "bar", NULL, "baz", NULL);
+ json_pack("[s*,o*,O*]", NULL, NULL, NULL);
+
 
 .. _apiref-unpack:
 

src/pack_unpack.c

@@ -235,6 +235,12 @@ static json_t *pack_object(scanner_t *s, va_list *ap)
  if(ours)
  jsonp_free(key);
 
+ if(strchr("soO", token(s)) && s->next_token.token == '*') {
+ next_token(s);
+ next_token(s);
+ continue;
+ }
+
  goto error;
  }
 
@@ -249,6 +255,8 @@ static json_t *pack_object(scanner_t *s, va_list *ap)
  if(ours)
  jsonp_free(key);
 
+ if(strchr("soO", token(s)) && s->next_token.token == '*')
+ next_token(s);
  next_token(s);
  }
 
@@ -273,14 +281,23 @@ static json_t *pack_array(scanner_t *s, va_list *ap)
  }
 
  value = pack(s, ap);
- if(!value)
+ if(!value) {
+ if(strchr("soO", token(s)) && s->next_token.token == '*') {
+ next_token(s);
+ next_token(s);
+ continue;
+ }
+
  goto error;
+ }
 
  if(json_array_append_new(array, value)) {
  set_error(s, "<internal>", "Unable to append to array");
  goto error;
  }
 
+ if(strchr("soO", token(s)) && s->next_token.token == '*')
+ next_token(s);
  next_token(s);
  }
  return array;

test/suites/api/test_pack.c

@@ -240,6 +240,18 @@ static void run_tests()
  fail("json_pack object refcount failed");
  json_decref(value);
 
+ /* object with optional members */
+ value = json_pack("{s:s,s:o,s:O}", "a", NULL, "b", NULL, "c", NULL);
+ if(value)
+ fail("json_pack object optional incorrectly succeeded");
+ value = json_pack("{s:**}", "a", NULL);
+ if(value)
+ fail("json_pack object optional invalid incorrectly succeeded");
+ value = json_pack("{s:s*,s:o*,s:O*}", "a", NULL, "b", NULL, "c", NULL);
+ if(!json_is_object(value) || json_object_size(value) != 0)
+ fail("json_pack object optional failed");
+ json_decref(value);
+
  /* simple array */
  value = json_pack("[i,i,i]", 0, 1, 2);
  if(!json_is_array(value) || json_array_size(value) != 3)
@@ -253,6 +265,18 @@ static void run_tests()
  }
  json_decref(value);
 
+ /* simple array with optional members */
+ value = json_pack("[s,o,O]", NULL, NULL, NULL);
+ if(value)
+ fail("json_pack array optional incorrectly succeeded");
+ value = json_pack("[**]", NULL);
+ if(value)
+ fail("json_pack array optional invalid incorrectly succeeded");
+ value = json_pack("[s*,o*,O*]", NULL, NULL, NULL);
+ if(!json_is_array(value) || json_array_size(value) != 0)
+ fail("json_pack array optional failed");
+ json_decref(value);
+
  /* Whitespace; regular string */
  value = json_pack(" s ", "test");
  if(!json_is_string(value) || strcmp("test", json_string_value(value)))