make datalink URL query more robust

examples/random_json_joke.m

@@ -0,0 +1,29 @@
+function jokes=random_json_joke(num, url)
+% this example shows how to use the _DataLink_ annotation defined in the
+% JData specification
+% (https://github.com/NeuroJSON/jdata/blob/master/JData_specification.md#data-referencing-and-links)
+% to define linked JSON/binary JSON data using external files or URL on the
+% web. In the below example, the jokeapi.dev feed returns a JSON record via
+% RESTFul URL, the returned record contains a subfield called `joke`, which
+% can be retrieved via the JSONPath $.joke attched after the URL, separated
+% by a collon. The general _DataLink_ URL is in the form of "URL:$jsonpath"
+
+if(nargin==0)
+    num=1;
+end
+
+if(nargin<2)
+    url='https://v2.jokeapi.dev/joke/Programming?type=single';
+end
+
+joke.(encodevarname('_DataLink_'))=[url ':$.joke'];
+jurl=savejson('',joke);
+
+jokes=cell(1,num);
+for i=1:num
+    jokes{i}=loadjson(jurl, 'maxlinklevel',1);
+end
+
+if(num==1)
+    jokes=jokes{1};
+end

jdatadecode.m

@@ -464,7 +464,7 @@
     if(opt.maxlinklevel>0 && isfield(data,N_('_DataLink_')))
         if(ischar(data.(N_('_DataLink_'))))
             datalink=data.(N_('_DataLink_'));
-            ref=regexp(datalink, '^(?<proto>[a-zA-Z]+://)*(?<path>[^:]+)(?<delim>\:)*(?<jsonpath>\$\d*\..*)*', 'names');
+            ref=regexp(datalink, '^(?<proto>[a-zA-Z]+://)*(?<path>.+)(?<delim>\:)()*(?<jsonpath>(?<=:)\$\d*\..*)*', 'names');
             if(~isempty(ref.path))
                 uripath=[ref.proto ref.path];
                 [fpath, fname, fext]=fileparts(uripath);