Function to print prettier parse exceptions

[Daniel-Diaz]

Using yaml sometimes I find unpleasant to read parse exceptions produced by print. The function implemented in this PR tries to mitigate this. It is incomplete, but I wanted to know if the idea is worth before spending more time with it.

[snoyberg]

That's hilarious, I was just discussing this with @dysinger 3 hours ago. Yes, this is very much a desired feature. And with the new displayException method, we can make it even nicer for users of GHC 7.10.

[Daniel-Diaz]

Oh, I forgot about the displayException method... I'll use that.

[snoyberg]

I'd recommend doing both a separate function and displayException, so that
users of older GHCs can still use it.

On Tue, Mar 31, 2015, 1:24 PM Daniel Díaz notifications@github.com wrote:

Oh, I forgot about the displayException method... I'll use that.

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#59 (comment).

[snoyberg]

Since I had another user asking about this, bumping. Are you still planning on implementing this?

[Daniel-Diaz]

My apologies. Travelling and work have kept me away from this.

I have included commits that finish implementing prettyPrintParseException, export it, and use it to implement displayException when compiling against base >= 4.8.0.0. I think YamlException can benefit from something like this too.

[Daniel-Diaz]

Note that when showing a NonStringKeyAlias exception, it's using show with a value of type Value. This can get very ugly.

[Daniel-Diaz]

Also, for the InvalidYaml case, a similar work for YamlException would make it look better. But I'd do that in a different PR.

[snoyberg]

Thanks!