fix string indentation, add option EmptyArrayAsNull, fix #91

Author: fangq

savejson.m

@@ -53,6 +53,8 @@
 %           SingletCell  [1|0]: if 1, always enclose a cell with "[]"
 %                         even it has only one element; if 0, brackets
 %                         are ignored when a cell has only 1 element.
+%           EmptyArrayAsNull  [0|1]: if set to 1, convert an empty array to
+%                         JSON null object; empty cells remain mapped to []
 %           ForceRootName [0|1]: when set to 1 and rootname is empty, savejson
 %                         will use the name of the passed obj variable as the
 %                         root object name; if obj is an expression and
@@ -157,6 +159,7 @@
 opt.arraytostruct = jsonopt('ArrayToStruct', 0, opt);
 opt.parselogical = jsonopt('ParseLogical', 0, opt);
 opt.arrayindent = jsonopt('ArrayIndent', 1, opt);
+opt.emptyarrayasnull = jsonopt('EmptyArrayAsNull', 0, opt);
 opt.inf = jsonopt('Inf', '"$1_Inf_"', opt);
 opt.nan = jsonopt('NaN', '"_NaN_"', opt);
 opt.num2cell_ = 0;
@@ -313,10 +316,8 @@
 if (~iscell(item) && ~isa(item, 'string'))
     error('input is not a cell or string array');
 end
-if (isa(item, 'string'))
-    level = level - 1;
-end
 isnum2cell = varargin{1}.num2cell_;
+
 if (isnum2cell)
     item = squeeze(item);
     if (~isvector(item))
@@ -325,10 +326,6 @@
 end
 
 dim = size(item);
-% if(ndims(squeeze(item))>2) % for 3D or higher dimensions, flatten to 2D for now
-%     item=reshape(item,dim(1),numel(item)/dim(1));
-%     dim=size(item);
-% end
 len = numel(item);
 ws = varargin{1}.whitespaces_;
 padding0 = repmat(ws.tab, 1, level);
@@ -741,7 +738,11 @@
 end
 
 if (isempty(mat))
-    txt = '[]';
+    if(varargin{1}.emptyarrayasnull)
+        txt='null';
+    else
+        txt = '[]';
+    end
     return
 end
 if (isinteger(mat))

test/run_jsonlab_test.m

@@ -157,6 +157,7 @@ function run_jsonlab_test(tests)
     test_jsonlab('output float format',@savejson,pi,'[3.142]','FloatFormat','%5.3f');
     test_jsonlab('remove singlet array',@savejson,{struct('a',1),5},'[{"a":1},5]','compact',1,'SingletArray',0);
     test_jsonlab('keep singlet array',@savejson,{struct('a',1),5},'[[{"a":[1]}],[5]]','compact',1,'SingletArray',1);
+    test_jsonlab('make null object roundtrip',@savejson,loadjson('{"a":null}'),'{"a":null}','EmptyArrayAsNull',1,'compact',1);
     test_jsonlab('test no datalink',@savejson,loadjson(savejson('a',struct(encodevarname('_DataLink_'),...
             '../examples/example2.json:$.glossary.title'))),'{"a":[{"_DataLink_":"../examples/example2.json:$.glossary.title"}]}','compact',1,'SingletArray',1);
     test_jsonlab('test maxlinklevel',@savejson,loadjson(savejson('a',struct(encodevarname('_DataLink_'),...