good diagnosis. want to make a ticket?
done: http://hackage.haskell.org/trac/ghc/ticket/4332 On second thought: is there any reason to use haskelline for *output*, as opposed to *input* history logging/editing? If not, avoiding that might be the easiest fix. Claus
| -----Original Message----- | From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell- | users-bounces@haskell.org] On Behalf Of Claus Reinke | Sent: 22 September 2010 16:05 | To: GHC users | Subject: Re: GHCi 6.12.3 stdout redirection works for :type, but not for | :info | | | > The problem is that my code for redirecting the output | > of GHCi commands still works for things like :type, but | > no longer for things like :info (this is my smallest example | > demonstrating the effect). | | The difference seems to be between commands that use | old-style GHCi output (works with redirection) versus | commands that output via Haskelline (redirection fails). | | ':type' calls typeOfExpr, which still uses 'printForUser', | which ultimately goes down to | 'compiler/utils/Pretty.lhs:printDoc', where it just calls | 'hPutChr/Str stdout'. | | ':info' calls 'info', which uses 'outputStrLn', which | ultimately goes down to | 'Haskelline/Backend/Win32.hsc:putOut', where it | calls either 'WriteConsole' (if to terminal), or | 'Data.ByteString.putStr' (no terminal). | | The distinction between terminal and no terminal | is currently done only once per GHCi session, so | redirecting stdout to a file for just one command | will call 'WriteConsole' on a non-terminal handle | (redirecting the whole session works, though it is | useless for writing advanced GHCi commands). | | I consider this a serious GHCi regression (never | mind the inconsistencies between GHCi commands), | as it breaks all the nice .ghci goodies from my old | tutorial (*) that people keep writing to me about. | | If this analysis is correct, possible fixes would be: | | - use 'printForUser/outputStrLn' consistently | (why is the latter needed for some commands, | but not for others?), and ensure that terminal | status is checked for each GHCi command, | instead of once per session (the main problem | is the version of 'putOut' that goes into the | 'RunTerm structure's 'putStrOut' field - it is | set by 'myRunTerm' in 'runInputTWithPrefs') | | - expose a GHCi command that allows users | to trigger Haskelline's terminal status check, | and rewrite the redirection code accordingly | | Sadly, I won't be able to implement either myself | at the moment - is there a chance of getting this | fixed for the 7.0.1 release (the first variant would | be the proper fix, the second variant a quick hack | to restore functionality)? | | Claus | | (*) http://haskell.org/haskellwiki/Ghci#Using_.ghci.2C_a_mini-tutorial | | > With the attached GHCi script defining a | > | > :redir <var> <command> | > | > command that should redirect the ouput of <command> | > into variable <var>, we get the output appended below | > (note the Exception for WriteConsole "handle is invalid", | > which is written into the temporary file when :info is | > called while stdout is redirected to that temporary file; | > in other words, the error message appears where the | > output of the command fails to appear). | > | > Is that an expected change with a known workaround, | > so that I just need to update my code, or is that | > unexpected behaviour that can only be fixed in GHCi? | > | > Claus | > | > PS. This is on Windows 7, if that matters. | > | > ------------- example session output | > $ ghcii.sh -ignore-dot-ghci | > GHCi, version 6.12.3: http://www.haskell.org/ghc/ :? for help | > .. | > Prelude> :cmd readFile "redir.script" | > Prelude> :redir x :t map | > .. | > Prelude> x | > "-- logging GHCi stdout\nmap :: (a -> b) -> [a] -> [b]\n" | > Prelude> :redir y :i map | > Prelude> y | > "-- logging GHCi stdout\n*** Exception: WriteConsole: invalid argument | > (Das | > Handle ist ung\252ltig.)\n" | > | | | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users