dhall-to-{json,yaml,yaml-ng}: Handle empty maps correctly

[sjakobi]

While generalizing list annotations In 0ee6ce6, I had forgotten to update dhall-json.

Fixes #1559.

This requires aeson-yaml >= 1.0.5.0 since older versions
incorrectly encode empty objects.

The raised bound also fixes #1560. A regression test is included.

[sjakobi]

Unfortunately dhall-to-yaml and dhall-to-yaml-ng disagree about how to encode empty objects:

  ./tasty/data/emptyMap
    HsYAML:     OK
    aeson-yaml: FAIL
      tasty/Main.hs:65:
      Conversion to YAML did not generate the expected output
      expected: "{}\n"
       but got: "\n"

Could you take a look at that @patrickmn?

[sjakobi]

I wonder whether we should update these defaultOptions to accurately reflect the default CLI options.

(In testDhallToJSON, we already use this Conversion by default:

dhall-haskell/dhall-json/tasty/Main.hs

Lines 69 to 74 in 6c68f82

	let mapKey = "mapKey"
	let mapValue = "mapValue"
	let conversion = Conversion {..}
	let convertedExpression =
	Dhall.JSON.convertToHomogeneousMaps conversion resolvedExpression

)

[sjakobi]

I have prepared a patch that adds a defaultConversion, that we could apply after this fix.

[Gabriella439]

Yeah, it would be a good idea to keep them in sync

[patrickmn]

Yep, will fix.

[sjakobi]

Yep, will fix.

Ping @patrickmn! :)

[sjakobi]

@patrickmn Any chance this could make it into the new release (#1575)?

[patrickmn]

Sorry, wasn't here much lately.

Yes, if it's just the empty objects and not the single vs. double-quoting right now I can push a change and release in the next hour or so.

[sjakobi]

No worries @patrickmn. I would really appreciate a fix for the empty-object encoding! :)

#1516 is less important IMHO.

[patrickmn]

Ok, should be fixed in 1.0.5.0 - clovyr/aeson-yaml@2b4abb1

[sjakobi]

Thanks for the fix @patrickmn! :)

[Gabriella439]

Yeah, it would be a good idea to keep them in sync