Another alternative would be to drop skipping of leading and trailing spaces. This would make the behaviour of the parsing functions more
#9150: libraries/time: parseTime barfs on leading space in format string -------------------------------------+------------------------------------- Reporter: mjo | Owner: Ashley Yakeley Type: bug | Status: new Priority: normal | Milestone: Component: libraries | Version: 7.8.2 (other) | Keywords: Resolution: | Operating System: Unknown/Multiple Differential Revisions: | Type of failure: Incorrect result Architecture: | at runtime Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | -------------------------------------+------------------------------------- Comment (by mjo): Replying to [comment:2 Ashley Yakeley]: predictable. However, the current behaviour has been there since time-1.1 from 2007, so programs that depend on it will fail with stricter functions. I assumed this was a bug because the behaviour changed between time-1.4.0.1 and time-1.4.2. I've narrowed down the change to time-1.4.0.1 -> time-1.4.0.2. Maybe I'm misunderstanding what you wrote, but your examples at least seem to parse fine with the older library. {{{ $ ghc-pkg list | grep time old-time-1.1.0.1 time-1.4.0.1 $ ghci ...
parseTime defaultTimeLocale "%Q " " " :: Maybe LocalTime Just 1970-01-01 00:00:00 parseTime defaultTimeLocale "%k" " 8" :: Maybe LocalTime Just 1970-01-01 08:00:00 }}}
The two examples in the description also both worked in earlier versions: {{{
parseTime defaultTimeLocale "%M " "15 " :: Maybe UTCTime Just 1970-01-01 00:15:00 UTC parseTime defaultTimeLocale " %M" " 15" :: Maybe UTCTime Just 1970-01-01 00:15:00 UTC }}}
Maybe there was a bug in time <= 1.4.0.1 that prevented the spaces from being skipped? For what it's worth, my use case is in pickling/unpickling XML. The package is now public at http://hackage.haskell.org/package/htsn-import. I have a test case that basically says, if we unpickle some XML and then repickle it, we should get what we started with. For that to work, the leading/trailing space needs to be preserved (I don't control the XML so I'm stuck with the spaces). I have a test case ensuring that, and with time-1.4.0.1 it passes. Once I upgraded the time library along with ghc, I noticed the failure. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9150#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler