Changing GHC Error Message Wrapping
Andrew Gibiansky
andrew.gibiansky at gmail.com
Fri Jan 10 14:26:38 UTC 2014
Thanks!
On Fri, Jan 10, 2014 at 9:21 AM, Simon Peyton Jones
<simonpj at microsoft.com>wrote:
> Crumbs. You are absolutely right. I’ll fix that. (It’s a relic from
> when the flags weren’t available to the show functions.)
>
>
>
> Simon
>
>
>
> *From:* Andrew Gibiansky [mailto:andrew.gibiansky at gmail.com]
> *Sent:* 08 January 2014 17:23
>
> *To:* Simon Peyton Jones
> *Cc:* Erik de Castro Lopo; ghc-devs at haskell.org
> *Subject:* Re: Changing GHC Error Message Wrapping
>
>
>
> Of course :) It made sense once I realized that the `show` was generating
> the string, and that it was not generated when the datatype was being
> constructed.
>
>
>
> However, I don't think the `showSDocForUser` call works (I tested). It
> uses `runSDoc` to generate a `Doc`. It then uses `show` on that Doc:
>
>
>
> instance Show Doc where
>
> showsPrec _ doc cont = showDoc doc cont
>
>
>
> Looking at `showDoc` we see:
>
>
>
> showDoc :: Doc -> String -> String
>
> showDoc doc rest = showDocWithAppend PageMode doc rest
>
>
>
> showDocWithAppend :: Mode -> Doc -> String -> String
>
> showDocWithAppend mode doc rest = fullRender mode 100 1.5 string_txt rest
> doc
>
>
>
> It ultimately calls `showDocWithAppend`, which calls `fullRender` with a
> hard-coded 100-column limit.
>
>
>
> -- Andrew
>
>
>
>
>
> On Wed, Jan 8, 2014 at 12:11 PM, Simon Peyton Jones <simonpj at microsoft.com>
> wrote:
>
> Well, the Show instance for a type (any type) cannot possibly respect
> pprCols. It can’t: show :: a -> String! No command-line inputs.
>
>
>
> I suggest something more like
>
>
>
> doc sdoc = do { dflags <- getDynFlags; unqual <- getPrintUnqual; return
> (showSDocForUser dflags unqual doc }
>
>
>
> Simon
>
>
>
> *From:* Andrew Gibiansky [mailto:andrew.gibiansky at gmail.com]
> *Sent:* 08 January 2014 00:09
>
>
> *To:* Simon Peyton Jones
> *Cc:* Erik de Castro Lopo; ghc-devs at haskell.org
> *Subject:* Re: Changing GHC Error Message Wrapping
>
>
>
> Hello all,
>
>
>
> I figured out that this isn't quite a bug and figured out how to do what I
> wanted. It turns out that the `Show` instance for SourceError does not
> respect `pprCols` - I don't know if that's a reasonable expectation
> (although it's what I expected). I ended up using the following code to
> print these messages:
>
>
>
> flip gcatch handler $ do
>
> runStmt "let f (x, y, z, w, e, r, d , ax, b ,c,ex ,g ,h) = (x :: Int)
> + y + z" RunToCompletion
>
> runStmt "f (1, 2, 3)" RunToCompletion
>
> return ()
>
> where
>
> handler :: SourceError -> Ghc ()
>
> handler srcerr = do
>
> let msgs = bagToList $ srcErrorMessages srcerr
>
> forM_ msgs $ \msg -> do
>
> s <- doc $ errMsgShortDoc msg
>
> liftIO $ putStrLn s
>
>
>
> doc :: GhcMonad m => SDoc -> m String
>
> doc sdoc = do
>
> flags <- getSessionDynFlags
>
> let cols = pprCols flags
>
> d = runSDoc sdoc (initSDocContext flags defaultUserStyle)
>
> return $ Pretty.fullRender Pretty.PageMode cols 1.5 string_txt "" d
>
> where
>
> string_txt :: Pretty.TextDetails -> String -> String
>
> string_txt (Pretty.Chr c) s = c:s
>
> string_txt (Pretty.Str s1) s2 = s1 ++ s2
>
> string_txt (Pretty.PStr s1) s2 = unpackFS s1 ++ s2
>
> string_txt (Pretty.LStr s1 _) s2 = unpackLitString s1 ++ s2
>
>
>
> As far as I can tell, there is no simpler way, every function in `Pretty`
> except for `fullRender` just assumes a default of 100-char lines.
>
>
>
> -- Andrew
>
>
>
> On Tue, Jan 7, 2014 at 11:29 AM, Andrew Gibiansky <
> andrew.gibiansky at gmail.com> wrote:
>
> Simon,
>
>
>
> That's exactly what I'm looking for! But it seems that doing it
> dynamically in the GHC API doesn't work (as in my first email where I tried
> to adjust pprCols via setSessionDynFlags).
>
>
>
> I'm going to look into the source as what ppr-cols=N actually sets and
> probably file a bug - because this seems like buggy behaviour...
>
>
>
> Andrew
>
>
>
> On Tue, Jan 7, 2014 at 4:14 AM, Simon Peyton Jones <simonpj at microsoft.com>
> wrote:
>
> -dppr-cols=N changes the width of the output page; you could try a large
> number there. There isn’t a setting meaning “infinity”, sadly.
>
>
>
> Simon
>
>
>
> *From:* Andrew Gibiansky [mailto:andrew.gibiansky at gmail.com]
> *Sent:* 07 January 2014 03:04
> *To:* Simon Peyton Jones
> *Cc:* Erik de Castro Lopo; ghc-devs at haskell.org
>
>
> *Subject:* Re: Changing GHC Error Message Wrapping
>
>
>
> Thanks Simon.
>
>
>
> In general I think multiline tuples should have many elements per line,
> but honestly the tuple case was a very specific example. If possible, I'd
> like to change the *overall* wrapping for *all* error messages - how does
> `sep` know when to break lines? there's clearly a numeric value for the
> number of columns somewhere, but where is it, and is it user-adjustable?
>
>
>
> For now I am just hacking around this by special-casing some error
> messages and "un-doing" the line wrapping by parsing the messages and
> joining lines back together.
>
>
>
> Thanks,
>
> Andrew
>
>
>
> On Mon, Jan 6, 2014 at 7:44 AM, Simon Peyton-Jones <simonpj at microsoft.com>
> wrote:
>
> I think it’s line 705 in types/TypeRep.lhs
>
>
>
> pprTcApp p pp tc tys
>
> | isTupleTyCon tc && tyConArity tc == length tys
>
> = pprPromotionQuote tc <>
>
> tupleParens (tupleTyConSort tc) (sep (punctuate comma (map (pp
> TopPrec) tys)))
>
>
>
> If you change ‘sep’ to ‘fsep’, you’ll get behaviour more akin to
> paragraph-filling (hence the “f”). Give it a try. You’ll get validation
> failure from the testsuite, but you can see whether you think the result is
> better or worse. In general, should multi-line tuples be printed with many
> elements per line, or just one?
>
>
>
> Simon
>
>
>
> *From:* ghc-devs [mailto:ghc-devs-bounces at haskell.org] *On Behalf Of *Andrew
> Gibiansky
> *Sent:* 04 January 2014 17:30
> *To:* Erik de Castro Lopo
> *Cc:* ghc-devs at haskell.org
> *Subject:* Re: Changing GHC Error Message Wrapping
>
>
>
> Apologize for the broken image formatting.
>
>
>
> With the code I posted above, I get the following output:
>
>
>
> Couldn't match expected type `(GHC.Types.Int,
>
> GHC.Types.Int,
>
> GHC.Types.Int,
>
> t0,
>
> t10,
>
> t20,
>
> t30,
>
> t40,
>
> t50,
>
> t60,
>
> t70,
>
> t80,
>
> t90)'
>
> with actual type `(t1, t2, t3)'
>
>
>
> I would like the types to be on the same line, or at least wrapped to a
> larger number of columns.
>
>
>
> Does anyone know how to do this, or where in the GHC source this wrapping
> is done?
>
>
>
> Thanks!
>
> Andrew
>
>
>
> On Sat, Jan 4, 2014 at 2:55 AM, Erik de Castro Lopo <mle+hs at mega-nerd.com>
> wrote:
>
> Carter Schonwald wrote:
>
> > hey andrew, your image link isn't working (i'm using gmail)
>
> I think the list software filters out image attachments.
>
> Erik
> --
> ----------------------------------------------------------------------
> Erik de Castro Lopo
> http://www.mega-nerd.com/
>
> _______________________________________________
> ghc-devs mailing list
> ghc-devs at haskell.org
> http://www.haskell.org/mailman/listinfo/ghc-devs
>
>
>
>
>
>
>
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/ghc-devs/attachments/20140110/092c7831/attachment-0001.html>
More information about the ghc-devs
mailing list