Limitations of java.util.Formatter (and String.format)

[sjrd]

After the big rewrite of #3380 and its numerous fixes, there are still a few things that are not supported in java.util.Formatter and therefore in String.format:

• Hexadecimal format for floating point numbers with %a.
• Formatting of BigIntegers and BigDecimals.
• Formatting of date/times with the %t. family.

The first two might be doable at some point. Formatting dates would bring in way to much code in every Scala.js application, and there are better APIs for that now in java.time anyway.

See also #3202 which records that %f, %e and %g have rounding discrepancies compared to the JVM.

[pfcoperez]

I had a patch for BigInteger formatter and I was opening an issue to describe what it fixes when I found this issue so I ended up not opening another one 😅

This is the PR with the patch fixing b.formatted("%d"), b.formatted("%o") and b.formatted("%x"): #4255

[sjrd]

An update here:

• BigInteger support was implemented in Add support for %o, %x and %d formats to BigInteger formatter #4255, as mentioned above.
• BigDecimal support was implemented in Implement formatting of BigDecimal values in j.u.Formatter. #4444.
• The %a conversion was implemented in Implement the 'a' conversion in java.util.Formatter. #4440.

In addition, the related issue #3202 was fixed in #4443.

That leaves only the date/time conversions, for which I have created a separate issue #4447.

So this one can be closed now.