fix(common): when transforming undefined numeric values

[Hareloo]

Transforming numeric values in validationpipe is incorrect when value is undefined

closes #12864

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

This issue occurs when using ValidationPipe with transform: true option set.
When this option is set and query/param arguments on an endpoint are used that are optional/have a default value, when no value/invalid value is passed to this query/URL param, it results in a NaN value, instead of the default value or having it be set to undefined in case it's an optional param.

Issue Number: #12864

What is the new behavior?

Values of the sort mentioned will now be parsed as undefined and converted to undefined.

Does this PR introduce a breaking change?

• Yes
• No

[coveralls]

Pull Request Test Coverage Report for Build 4421a15f-4fad-4fed-a0b6-753367b142e5

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.002%) to 92.26%

---

Totals
Change from base Build 2893054b-b3fe-4fee-a01d-9c529a7f6e46:	0.002%
Covered Lines:	6699
Relevant Lines:	7261

---

💛 - Coveralls

[caiorosa-seenons]

@Hareloo the same issue happens for other types such as Enums and Strings, on both @query and @param decorations.
I'll try to provide a subset of a project I'm working on (I'm currently migrating to swc, so that's how I caught it).

Small example:

 public async get(
    @Query('status', new ParseEnumPipe(MyStatusEnum, { optional: true })) status?: MyStatusEnum,
  ): Promise<ResponseModel> {
   ...
}

https://github.com/nestjs/nest/blob/master/packages/common/pipes/parse-enum.pipe.ts

[benjGam]

Nice change.

[adiadiushko]

Suggested change

	if (metatype === Number) {
	if (isUndefined(value)) {
	// This is a workaround to deal with optional numeric values since
	// optional numerics shouldn't be parsed to a valid number when
	// they were not defined
	return undefined;
	}
	return +value;
	}
	// This is a workaround to deal with optional numeric values since
	// optional numerics shouldn't be parsed to a valid number when
	// they were not defined
	if (metatype === Number && !isUndefined(value)) {
	return +value;
	}

[arabold]

The original change by @Hareloo is actually a 1:1 match with the implementation checking for Boolean type a few lines above. IMO the code is fine as is as it mirrors that code and follows the same pattern (without saying whether that's a good or a bad pattern 🤷).

If we change it here then we should also change the Boolean implementation as well.

[stuarthimmer-loop]

Is this change still blocked?

[kamilmysliwiec]

@stuarthimmer-loop it's a breaking change so we'll need to wait till the next major release