add tests for [hackage]

[chris48s]

Note there is no check for the 'not found' case on the hackage-deps endpoint.

• A package where all the dependencies are up-to-date returns an empty feed: http://packdeps.haskellers.com/feed/AbortT-mtl
• ..and a package that doesn't exist returns an empty feed: http://packdeps.haskellers.com/feed/not-a-package

In order to add a not found case, we'd have to add a second API call so that the hackage-deps endpoint calls https://hackage.haskell.org/ first to check if the package exists and then makes a subsequent call to http://packdeps.haskellers.com if it does. Is it worth adding that additional overhead to cover the not found case?

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[paulmelnikow]

Hmm, returning up to date when the package name is misspelled seems pretty bad!

How about opening an issue at https://github.com/snoyberg/packdeps? If they could provide a way to distinguish them, and that could be resolved fairly quickly, that seems like a good way to go. Maybe they could even add a JSON API? 😀

FWIW the website is able to distinguish the two:

http://packdeps.haskellers.com/feed?needle=not-a-package
http://packdeps.haskellers.com/feed?needle=AbortT-mtlz

[chris48s]

I've raised an issue for it: snoyberg/packdeps#35 We'll see where it goes..

In terms of other options:

• I did also have a look to see if we could switch to libraries.io as an alternate source for this, but unfortunately not: Add dependency collection for projects on Hackage librariesio/libraries.io#1579

• We could do it in one request by calling the website and parsing the HTML. We don't need write a full 'scraper' for it - we could just call http://packdeps.haskellers.com/reverse/lens and grep for the string class="out-of-date". This endpoint also usefully throws a 404 for an invalid request: http://packdeps.haskellers.com/reverse/not-a-package

• If the nicest way is to use 2 HTTP requests to pick this up is that necessarily a disaster? There does seem to at least one or 2 other badges which make >1 request e.g: codeclimate (coverage + maintainability).

[chris48s]

I have no objection, but also don't have time to write the change myself. If you're able to write a PR, it has a nice better chance of happening.

Not sure how your Haskell is.. Perhaps if the issue was "/feed endpoint should calculate Nth fibonacci number" I might have a chance 😀

I reckon its time for Plan B.

[paulmelnikow]

I'd love to give this an hour since it sounds like a fun challenge, though I'll resist the temptation. 😀

Worth leaving the issue open in case someone comes along to address it. Meanwhile two requests seems a fine way to handle this. Perhaps we could make the second request to one of his other routes. That way we know the data is in sync between the two checks.

e.g.

http://packdeps.haskellers.com/licenses/AbortT-mtl <- exists, 200
http://packdeps.haskellers.com/licenses/AbortT-mtlz <- doesn't exist, 404

[chris48s]

sorted :)

[paulmelnikow]

Looks great!

One last change I'd suggest while you're in here: change hackage-deps to dependencies for consistency with the other dependency badges.

[chris48s]

Test failure is unrelated to this PR

floatdrop/pinkie-promise#4

pinkie-promise is a transitive dependency of other packages so this will probably take a while to settle out. Also note there may be some squatting going on: floatdrop/pinkie-promise#4 (comment)

[paulmelnikow]

This came out looking really good. Nice work!