Add checkbox to download JSON instead of starting ZApp, useful for command-line use

zoe_api/web/static/zoe.css

@@ -180,6 +180,12 @@ form#zapp_start_form input {
     font-family: "Lucida Console", Monaco, monospace;
 }
 
+form#zapp_start_form label.label-inline,
+form#zapp_start_form label.label-inline input {
+    font-variant: normal;
+    display: inline;
+}
+
 /* footer */
 
 div.status_line {

zoe_api/web/templates/zapp_start.html

@@ -37,11 +37,21 @@
         <label>{{ param.readable_name }}:&nbsp;
         <input name="{{ param.name }}" value="{{ param.default if param.default != None }}" required title="{{ param.description }}" size="128"/></label><br/>
     {% endfor %}
-        <button type="submit">Start</button>
+        <label class="label-inline"><input type="checkbox" onchange="set_submit_text(this)" name="download_json"> Download JSON with these parameters for command-line execution</label>
+        <br><br>
+        <button id="submit" type="submit">Start</button>
     </form>
 
     <script>
         $("#zapp_start_form").validate();
+
+        function set_submit_text(elem) {
+            if (elem.checked) {
+                $("#submit").text("Download JSON");
+            } else {
+                $("#submit").text("Start");
+            }
+        }
     </script>
 
     <p><a href="{{ reverse_url("zappshop") }}">Back to the ZApp shop</a></p>

zoe_api/web/zapp_shop.py

@@ -109,7 +109,15 @@ class ZAppStartWeb(ZoeRequestHandler):
 
         app_descr = self._set_parameters(zapp.zoe_description, zapp.parameters)
 
-        new_id = self.api_endpoint.execution_start(uid, role, exec_name, app_descr)
+        download_json = self.get_argument('download_json')
+        if download_json:
+            self.set_header('Content-Type', 'application/json')
+            self.set_header('Content-Disposition', 'attachment; filename={}.json'.format(zapp_id))
+            self.write(app_descr)
+            self.finish()
+            return
+        else:
+            new_id = self.api_endpoint.execution_start(uid, role, exec_name, app_descr)
 
         self.redirect(self.reverse_url('execution_inspect', new_id))