Value is not preserved across flow breaking commands

[aneilbaboo]

In a flow which contains a flow-breaking command, such as the following, special returned value is not preserved across the break. Here, a break is created by invoking a dialog. Notice how the value returned by Dialog1 is lost after the break.

We should fix this.

onStart: [
  { start: "Dialog1", // returns "v1"         flowPath = [onStart,start(Dialog1)] 
    then: [  // value="v1"                    flowPath = [onStart,start(Dialog1),then] 

      // starting Dialog2 breaks the flow (Dialog2 starts a new flow)
      {  start: "Dialog2", // returns "v1"    flowPath = [onStart,start(Dialog1),then,start(Dialog2)] 
          then: [ // value="v2" here          flowPath = [onStart,start(Dialog1),then,start(Dialog2),then] 
          ]
      },
      // this is the nextFlow of the "onStart.start(Dialog1).then" flow
      "Value is {{value}}"  // expecting this to send message "Value is v1", 
                            // but bot sends "Value is undefined"
                          
    ]
]

One solution is to:

1. Detect whether flow has a next flow
2. If value is set in the flow, save it to a hidden variable before each flow breaker
   E.g., save value v1 in flow onStart.start(Dialog.then to a local session var, such as:
   "__value__:onStart.start(Dialog1).then" = "v1"
   This would happen just before {start: "Dialog2" ...}
3. Load the value at the beginning of the nextFlow
4. clear the value at the end of the last nextFlow