%_H%M format fails to parse space-padded hour followed by minutes " 731"

[knoc-off]

The format string "%_H%M" fails to parse the input " 731" (space + 7 + 31). According to the documentation, %_H should handle space-padded hours and %M should parse the following minutes, but the parser appears unable to correctly separate the hour from the minutes when using space padding.

here is a playground link:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=a8de6a451e19206a86142264531042b8

what im expecting: " 731" -> hour 7, minute 31

[djc]

I'm unlikely to have time to look into this as a volunteer. Happy to review a PR, or contact me privately for commercial rates.

[knoc-off]

I would be happy to support. but would like to clarify whether this behavior is actually intended or should be considered a bug.

From what I can tell, the parsing is acting greedily, %_H consumes more than expected and doesn’t leave room for %M to parse correctly.

And there’s also a potentially related, open issue here:
#1399

Not even sure if it can even be done in a backwards-compatible way.

Could you confirm whether this is indeed a bug, or if the current greedy parsing is by design?

[djc]

The design is pretty much lost to history and the expectation that %_H%M can parse 731 seems reasonable, but the question is how much complexity would be needed to make this work and how much fallout there would be. The best way to get a feeling for both is making the change and getting the suite passing.