Support tagged nodes

[EdwarDDay]

• implement Support Polymorphic serialization #4
• support yaml tags for polymorphic de-/serialization

[charleskorn]

Hey @EdwarDDay, thanks for the PR! Before I take a closer look, could you please fix the compilation error Travis is reporting?

[codecov-io]

Codecov Report

Merging #7 into master will increase coverage by 0.14%.
The diff coverage is 92.15%.

@@             Coverage Diff             @@
##             master      #7      +/-   ##
===========================================
+ Coverage     93.55%   93.7%   +0.14%     
- Complexity      101     108       +7     
===========================================
  Files             9       9              
  Lines           388     429      +41     
  Branches         76      85       +9     
===========================================
+ Hits            363     402      +39     
- Misses           10      13       +3     
+ Partials         15      14       -1

Impacted Files	Coverage Δ	Complexity Δ
src/main/kotlin/com/charleskorn/kaml/YamlNode.kt	100% <100%> (ø)	1 <0> (ø)	⬇️
...main/kotlin/com/charleskorn/kaml/YamlNodeReader.kt	88.57% <100%> (+0.16%)	42 <1> (+1)	⬆️
src/main/kotlin/com/charleskorn/kaml/Yaml.kt	87.5% <100%> (ø)	5 <0> (ø)	⬇️
src/main/kotlin/com/charleskorn/kaml/YamlInput.kt	92.3% <86.95%> (-0.34%)	1 <0> (ø)
src/main/kotlin/com/charleskorn/kaml/YamlOutput.kt	95.55% <93.75%> (+1.8%)	30 <10> (+6)	⬆️

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[charleskorn]

To make the intent of this test clear, could you remove the { } and replace it with a string (eg. !<sealedInt> thing: something)?

[EdwarDDay]

That's not yet possible, but I can create another PR after that one. Currently scalar nodes with tags are not supported and supporting them would be a new feature with a new PR in my opinion.

[charleskorn]

Is there any way to support !sealedInt instead of !<sealedInt>?

[EdwarDDay]

I think that can be done via the %TAG directive, but I'm not sure how to do that.

[charleskorn]

Hey @EdwarDDay, thanks for incorporating my feedback and apologies for the delay in getting back to you. This is looking really good. The only things I'd like to see before I merge this are:

• More tests for reading tagged input nodes - for example, the logic in YamlTaggedInput.getCurrentLocation() is never exercised (take a look at the tests for other kinds of nodes for how this is used to generate exceptions with location information) and none of the scalar decoding methods (eg. decodeInt()) are exercised. I'm not suggesting to test these scalar decoding methods individually, but it does seem that they're not being used by the current tests which suggests they might not be necessary and can be removed.

• If the scalar decoding methods are required, I'd like to see them simplified a bit to remove the duplication and risk of things getting out of sync - for example, I'm imagining decodeInt() could look something like:

  override fun decodeInt(): Int = decodeScalar { decodeInt() }

  where decodeScalar is a private inline function that does the check for the current index and picks the appropriate decoder

[EdwarDDay]

I removed the decode[Int|Short|Unit|...] methods, because these are not yet used. The getCurrentLocation() is now tested. Additionally a tag is ignored, if it is not needed.

[charleskorn]

Looks good to me, thanks @EdwarDDay!