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purescript / psc-package

A package manager for PureScript based on package sets
https://psc-package.readthedocs.io
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more helpful parsing errors possible than "unable to parse packages.json"? #57

Closed mjhoy closed 7 years ago

mjhoy commented 7 years ago

Hi,

I'm using psc-package with a forked package-set. I am running into this error, which was pretty unhelpful. Is it possible to get better parsing errors? I played around with Aeson but the best I could get with eitherDecodeStrict was "Error in $: Failed reading: not a valid json value". I am not that familiar with Aeson so maybe there is a better solution?

This also applies to psc-package.json, I believe.

hdgarrood commented 7 years ago

I think Aeson's errors are generally good when the JSON is valid but the schema does not match (e.g. found a string where a number was expected), but not so good for invalid JSON. Looking at the response to a similar issue, though, it seems that the Aeson maintainers would be open to a PR improving this; that's probably the best approach to addressing this issue, I think.

mjhoy commented 7 years ago

this package might be worth considering as an alternative: https://github.com/FPBrno/aeson-parsec-picky

mjhoy commented 7 years ago

also, might be worth switch to eitherDecodeStrict in either case, from decodeStrict, and printing out the error message, which is more helpful in the event of valid json but an invalid schema, e.g.:

Error in $['dom-geolocation']: key "repo" not present
hdgarrood commented 7 years ago

I don't think we should adopt a library which is more picky than what would be accepted by most other JSON parsers.

mjhoy commented 7 years ago

yeah, that's unfortunate.

i wonder if, ultimately, JSON is the right format to use here. psc-package makes a lot of sense to me, as i'm a little familiar with nixpkgs, but the process of manipulating json to, say, add missing packages or change forked package definitions, seems a little less than ideal and not really was json is designed for. but maybe i just need to turn on my emacs flycheck json mode :)

paf31 commented 7 years ago

Fixed in 0.2.3, thanks.