fix(core): Fix decimal pipe floating point formatting bug

[injae-kim]

PR Type

• Bugfix

What is the current behavior?

Input (string) : "123456789.123456789"
Format : 0.0-9
Output :   123,456,789.12345679 // 7(8)9 -> 8 is lost..
Expected : 123,456,789.123456789

angular/packages/common/src/pipes/number_pipe.ts

Lines 104 to 105 in d315e2c

	const num = strToNumber(value);
	return formatNumber(num, locale, digitsInfo);

• Currently, decimal_pipe parse string to number first and then apply formating
  • ⚠️ When parse '123456789.123456789' string to number, some digit on fraction part is lost due to javascript floating point limitation
• Issue Number: Decimal Pipe not formatting value correctly #47809
  • Reproduce: https://stackblitz.com/edit/angular-ivy-ycarro?file=src/app/app.component.html

What is the new behavior?

        const formatStrs = [integerPart, fractionPart]
            .map(part => strToNumber(part))
            .map(num => formatNumber(num, locale, digitsInfo));

• To format string to number on javascript well, apply formatting on integer/fraction part separately and then concat, return it.

Does this PR introduce a breaking change?

• No

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[JeanMeche]

The condition doesn't cover every non valid string, we should likely rely on strToNumber to throw.

[injae-kim]

      if (typeof value === 'string' && value.includes('.') && strToNumber(value)) {
        const parts = value.split('.');
        const integerPart = parts[0];
        const fractionPart = `0.${parts[1]}`;
        ..

Hmm you mean calling strToNumber(value) inside of if(..)?
Or can you give some example code? 🙇

Cause parts is array of string, we can't pass it to strToNumber(string) directly 🤔

[JeanMeche]

We can either call strToNumber() or probably better, extract the portion we'd like to reuse in a function :

function isStringNumber(value: number|string): boolean {
  return typeof value === 'string' && !isNaN(Number(value) - parseFloat(value))
}

[injae-kim]

aha~ I understood. isStringNumber looks much better! thanks for nice suggestion 👍

[injae-kim]

I need this feature and ready to update PR, so waiting your awesome reviews~ thanks! 😃