cdk diff not picking up differences if old/new value is in format x.y.z

[johfer-bd]

"cdk diff" in the current version (1.117.0 / 2.0.0-rc.16) doesn't pick up differences if the old/new value has a number-like format but actually isn't a number (e.g. 0.31.1)

What did you expect to happen?

I expected the differences are picked up and shown

What actually happened?

I received "There are no differences"

Environment

• **CDK CLI Version : 2.0.0-rc.16
• Node.js Version: 14.17.0
• OS : MacOs
• Language (Version): TypeScript (4.1.3)

[johfer-bd]

Ok, I looked into this and the culprit is this part in the deepEqual function that compares the old and new template:

aws-cdk/packages/@aws-cdk/cloudformation-diff/lib/diff/util.ts

Line 27 in a04c017

safeParseFloat(lvalue) === safeParseFloat(rvalue)) {

// allows a numeric 10 and a literal "10" to be equivalent;
  // this is consistent with CloudFormation.
  if ((typeof lvalue === 'string' || typeof rvalue === 'string') &&
      safeParseFloat(lvalue) === safeParseFloat(rvalue)) {
    return true;
  }

In my case lvalue and rvalue are two version strings like "0.31.1-prod" and "0.31.2-prod" which are both parsed into "0.31" (and hence considered equal).

[johfer-bd]

I think this can be handled as edge case in safeParseFloat which already makes provisions for things like "0.0" but not for "0.1.something", or "1 something", or whatever is parsed by parseFloat into a (finite) number but actually isn't a number.

[vincent-turato]

I would like to submit a PR for this. Should be finished tomorrow.

[github-actions]

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