Extend Builtin Format function

batavia/builtins/format.js

@@ -1,4 +1,5 @@
 var exceptions = require('../core').exceptions
+var callables = require('../core').callables
 
 function format(args, kwargs) {
     if (arguments.length !== 2) {
@@ -14,14 +15,33 @@ function format(args, kwargs) {
             'format() takes at most 2 arguments (' + args.length + ' given)'
         )
     }
+    if (args[1] === "" || args[1] === undefined) {
+        return args[0];
+    }
     if (!args[0].__format__) {
         throw new exceptions.BataviaError.$pyclass(
             '__format__ not implemented for this type.'
         )
     }
+    let stringAutoFormat;
+    if (stringAutoFormat = stringFormatStandIn(args)) { // See if __format__ is implemented or a stub - TODD: remove
+        return stringAutoFormat;                        // If it's a stub, send the formatting to "".format()
+    }
     return args[0].__format__(args[0], args[1]) // TODO: Implement the __format__ function for types like int and string, where it actually can do something
 }
 
+function stringFormatStandIn(args) {
+    const callables = require('../core').callables;
+    let result = false;
+    try {
+        args[0].__format__(args[0], args[1]);
+    } catch (error) {
+        if(error.toString() === "TypeError: Cannot read property '$pyclass' of undefined"){
+            return callables.call_method('{:' + args[1] + '}', 'format', [args[0]], {});
+        }
+    }
+    return result;
+}
 format.__doc__ = 'Return value.__format__(format_spec)\n\nformat_spec defaults to the empty string'
 
-module.exports = format
+module.exports = format;