Bug 17459 – format("%012,3d", ...) doesn't handle field width and zero-padding correctly

Code: -------- import std.stdio; void main() { writefln("%012,3d", 100); writefln("%012,3d", 1_000); writefln("%012,3d", 100_000); writefln("%012,3d", 1_000_000); writefln("%012,3d", 100_000_000); } -------- Expected output: -------- 0000,000,100 0000,001,000 0000,100,000 0001,000,000 0100,000,000 -------- Actual output: -------- 00000000100 00000001,000 0000100,000 0001,000,000 100,000,000 -------- Note the uneven field widths in the output. In particular, output lines 1, 3, 5 are 1 character shorter than the specified field width of 12. If "%012d" were used as format string instead, the output is correctly padded to 12 characters. Also, it would be nice if the comma separators were also inserted into the zero padding so that multiple values printed with the same format would have separators nicely lined up. But this point is more arguable, because it's not clear what should happen if the separator falls on the first character of the output, since printing ",000,000,100" for the first line would look rather strange. But not printing the comma means the zero padding causes a 4-digit grouping rather than the requested 3-digit grouping. I'm not sure what's the correct solution.

Commit pushed to master at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/9352627f89348a4479114a5bcdc64cf35c0957bf Fix for problems with format seperators fix issue 17459 fix issue 18047 This is in one commit as the two problem are located at the place andrei review

Commit pushed to stable at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/9352627f89348a4479114a5bcdc64cf35c0957bf Fix for problems with format seperators