Disable messages with GHC API

Matthew Pickering matthewtpickering at gmail.com
Fri Feb 3 15:59:09 UTC 2017

You are right. I looked more closely now and it looks like
"parseModule" and so on overwrite the DynFlags with a cached version
before running the relevant piece of the pipeline.

 857    hsc_env <- getSession
 858    let hsc_env_tmp = hsc_env { hsc_dflags = ms_hspp_opts ms }
 859    hpm <- liftIO $ hscParse hsc_env_tmp ms

I think this is symptom of the fact that DynFlags is not very well
structured and a lot of different compiler options are lumped
together. It makes sense that we need to use the right DynFlags to run
the module but this shouldn't overwrite things which are irrelevant
like log_action.


On Fri, Feb 3, 2017 at 3:30 PM, Christopher Done <chrisdone at gmail.com> wrote:
> Adding `handleSourceError` around it makes no difference.
> Which makes sense, as I don't think warnings count as exceptions,
> otherwise my code would never have completed in the first place.
> On 3 February 2017 at 12:50, Matthew Pickering
> <matthewtpickering at gmail.com> wrote:
>> The errors are eventually caught and printed by "handleSourceError"
>> which is used a few times in your code. You could either modify one of
>> these to not print out any errors or try something more intelligent
>> like is in `parUpsweep_one` which does use the `log_action` in order
>> to print the errors out.
>> On Fri, Feb 3, 2017 at 12:21 PM, Christopher Done <chrisdone at gmail.com> wrote:
>>> In Intero, after loading modules, for each one I run the following
>>> function: https://github.com/commercialhaskell/intero/blob/300ac5a/src/GhciInfo.hs#L75..L85
>>> If there are warnings or any output, they get outputted. As they are
>>> already outputted by regular :load, I don’t need the same output
>>> twice.
>>> How do I disable non-severe output for any GhcMonad m => m a? I’m
>>> using GHC 8.0.1 presently.
>>> I tried the following before calling getModInfo, expecting there to be
>>> no output anymore:
>>> +      GHC.setSessionDynFlags
>>> +        df {log_action = \ref dflags severity srcSpan style msg -> return ()}
>>> And this had no effect. I tried some other things but ran out of
>>> patience to keep a record of them all.
>>> Ciao!
>>> _______________________________________________
>>> ghc-devs mailing list
>>> ghc-devs at haskell.org
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