convo.repeat() in handler causes 'TypeError: Converting circular structure to JSON' in conversationState.saveChanges

[etiennellipse]

Are you sure this is an issue with the Botkit core module?

Yes

What are you trying to achieve or the steps to reproduce?

I am trying to repeat a step in a conversation. However, if a question was asked before, the repeat() method will cause a crash.

Reproduction steps:

• Copy this skill in a web bot
• Say "go" to fire the dialog
• Answer the first question, for which the result will be saved in the conversation state
• Then, say "repeat" which will fire convo.repeat() and crash

const { BotkitConversation } = require('botkit');

module.exports = function(controller) {
    const DIALOG_SUBJECT_ID = 'subject-dialog';

    const subjectDialog = new BotkitConversation(DIALOG_SUBJECT_ID, controller);

    subjectDialog.ask(`First question`, [], `first`);

    for (let i = 0; i < 30; i++) {
        subjectDialog.ask(`Message #${i}`,
            async (response, convo, bot) => {
                if (response === 'repeat') {
                    convo.repeat();
                }
            }, `conv-${i}`);
    }

    controller.addDialog(subjectDialog);

    controller.hears('go', ['message', 'direct_message'], async (bot, message) => {
        await bot.beginDialog(DIALOG_SUBJECT_ID);
    });

};

What was the result you received?

Error:

(node:97694) UnhandledPromiseRejectionWarning: TypeError: Converting circular structure to JSON
    at JSON.stringify (<anonymous>)
    at Object.calculateChangeHash (/Users/etienne/Code/botkit-example/node_modules/botbuilder-core/lib/storage.js:29:17)
    at BotkitConversationState.saveChanges (/Users/etienne/Code/botkit-example/node_modules/botbuilder-core/lib/botState.js:89:59)
    at Botkit.<anonymous> (/Users/etienne/Code/botkit-example/node_modules/botkit/lib/core.js:507:42)
    at Generator.next (<anonymous>)
    at /Users/etienne/Code/botkit-example/node_modules/botkit/lib/core.js:7:71
    at new Promise (<anonymous>)
    at __awaiter (/Users/etienne/Code/botkit-example/node_modules/botkit/lib/core.js:3:12)
    at Botkit.saveState (/Users/etienne/Code/botkit-example/node_modules/botkit/lib/core.js:506:16)
    at Botkit.<anonymous> (/Users/etienne/Code/botkit-example/node_modules/botkit/lib/core.js:491:44)

What did you expect?

Repeat the previous message

Context:

• Botkit version: 4.5.0
• Messaging Platform: Web
• Node version: 10.16.3
• Os: MacOS

Inspecting the execution shows that in BotState.saveChanges the cached instance has a circular reference on the "first" value pointing to the "values" object, bot should contain the value of the answer given.

[etiennellipse]

The comment #1673 (comment) refers to the same issue.

[etiennellipse]

Investigating further.

When convo.repeat() is used, the BotkitConversation.onStep() method is called twice, the second time the step.result contains the whole step.values object. In the onStep method line 586 to 590, the result is captured into the step.values for the previous step; that's when things go wrong.

So I was looking at those calls in conversation.ts:

// did we just change threads? if so, restart this turn
                if (index !== step.index || thread_name !== step.thread) {
                    return await this.runStep(dc, step.index, step.thread, DialogReason.nextCalled, step.values);
                }

I don't understand why the step.values is passed as the result parameter here. The onStep method seems to expect the result from the last interaction. That's as far as I could go today!

[benbrown]

Great digging! super helpful.

I will have to experiment and do more investigation - it may be incorrect to pass this in instead of simply forwarding result

[benbrown]

OK I am able to reproduce this reliably.

It seems to be tied to having 2 calls to convo.ask in a row, and calling repeat from one of them...

If there is a call to say in between 2 asks, it is ok.

HRRM!

[benbrown]

@etiennellipse I think your original diagnosis was correct!

[benbrown]

will be fixed in 4.6