[Issue 24164] New: readf should stop reading a trailing string at whitespace

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24164

          Issue ID: 24164
           Summary: readf should stop reading a trailing string at
                    whitespace
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: schveiguy at gmail.com

scanf for strings stops at whitespace. readf does not.

This shouldn't be too much of a problem, because the %s could be followed by
something else, and that match would eagerly go to the next thing.

But for a trailing %s, with a string as the target, the result is that string
is filled with the *rest of the stream*. That makes no sense, and is a land
mine for people who aren't familiar with readf. Not only that, but using readf
to consume the rest of the file into a string doesn't seem like a great use
case to support.

I propose that readf, when presented with a format that ends in %s, and whose
matching type is a string, should stop when a whitespace character is
encountered.

I know this is an inconsistency and special case. It could be done potentially
in a way to avoid special cases (like send to the processing function a boolean
saying nothing is left in the format string), but it should be done this way.

Alternatively, this could be considered a runtime error.

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