(core): Slow execution at SynthUtils.toCloudFormation on v1.57.0 cont.

[idm-ryou]

This is the second time opening issue that I report SynthUtil.toCloudFormation is slow. The first issue was #10213, and the fixes made execution a bit faster, but it is still much slower (about x10) compared to the implementation of @aws-cdk/assert v1.56.

• v1.56: $ jest took 12 secs
• v1.89: $ cdk synth took 12 secs
• v1.89: $ jest took 130 secs

Reproduction Steps

import * as cdk from "@aws-cdk/core";
import "@aws-cdk/assert/jest";
import { SynthUtils } from "@aws-cdk/assert"; // 1.89
// Codes of @aws-cdk/assert v1.56 are copied to local files to switch implementations
// import { SynthUtils } from "./cdk-copy/assert/lib" // 1.56
import { app } from "./app";

describe("app", () => {
  const stacks = app.node.children
    .filter(cdk.Stack.isStack);

  test("stack templates match snapshots", () => {
    stacks.forEach((stack) => {
      expect(SynthUtils.toCloudFormation(stack)).toMatchSnapshot(
        stack.stackName
      );
    });
  });
});

What did you expect to happen?

Execution time is about same as v1.56 and pretty much equivalent to cdk synth

What actually happened?

Execution time is about x10 slower compared to v1.56 and simple cdk synth

Environment

• CDK CLI Version : 1.89.0
• Framework Version: 1.89.0
• Node.js Version: v15.8.0, v12.20.1
• OS : macOS, Linux
• Language (Version): TypeScript 4.1.3

Other

Here are Node.js profiling results.

• v1.56(fast)
• v1.89(slow)

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This is 🐛 Bug Report

[idm-ryou]

Using assertions.Template.toJSON addressed this issue now.

[github-actions]

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