Allow parsing empty files without throwing error

[andrew-smartnews]

I'd like to be able to pass in empty files and not have the yml parser throw, such as:

Caused by: java.lang.IllegalArgumentException: Expected document start at  in 'reader', line 1, column 1:
    
    ^
	at com.sksamuel.hoplite.yaml.YamlParser.load(YamlParser.kt:38)
	at com.sksamuel.hoplite.sources.ConfigFilePropertySource$node$1.invoke(ConfigFilePropertySource.kt:36)
	at com.sksamuel.hoplite.sources.ConfigFilePropertySource$node$1.invoke(ConfigFilePropertySource.kt:36)
	at com.sksamuel.hoplite.fp.Validated$Companion.ap(Validated.kt:70)
	at com.sksamuel.hoplite.sources.ConfigFilePropertySource.node(ConfigFilePropertySource.kt:36)
	at com.sksamuel.hoplite.NodeParser.parseNode(NodeParser.kt:29)
	at com.sksamuel.hoplite.ConfigLoader.loadConfig(ConfigLoader.kt:136)
	at com.smartnews.cg.configuration.BuildConfigKt.<clinit>(BuildConfig.kt:169)
	... 3 more

What do you think?

[sksamuel]

Sounds like a good idea.

[andrew-smartnews]

Awesome I'll post up a PR (on my personal account, this is my work account)

[andrew-smartnews]

Looks like I can't post PRs here, but I think I got most of the way there - got a bit stuck with the generics, but would love your opinion on how to close this out. I added the following:

1. In ConfigFailure.kt:

data class EmptySource(val source: String) : ConfigFailure {
  override fun description(): String = "Source $source is empty"
}

2. In ConfigFilePropertySource.kt, changed the node method to:

override fun node(context: PropertySourceContext): ConfigResult<Node> {
    val parser = context.parsers.locate(config.ext())
    return Validated.ap(parser, config.open()) { a, b -> if (b.available() > 0) b.use { a.load(it, config.describe()) } else ConfigFailure.EmptySource(config.describe()).invalid() }
      .mapInvalid { ConfigFailure.MultipleFailures(it) }
      .flatRecover { if (optional) Undefined.valid() else it.invalid() }
  }

Won't compile to a generics issue, but I think it's pretty close. Thoughts?

[sksamuel]

What's the error ?

[sksamuel]

I am ready to release 2.6.0
If you want to finish this I can include it, or I can add it myself if you wish.
@andrew-smartnews

[andrew-smartnews]

I'd love to get this added so I can begin using it right away (all my config files have "THIS FILE CANNOT BE LEFT BLANK" right now for the ones that aren't yet filled in, which is not ideal!)

The error my change is giving me is:

Type mismatch.
Required:
ConfigResult<Node> /* = Validated<ConfigFailure, Node> */
Found:
Validated<ConfigFailure.MultipleFailures, Any>

My change is returning Validated<ConfigFailure.MultipleFailures, Any> vs. the expected Validated<ConfigFailure, Node>, and I can't quite figure out how to make it happy. Since it doesn't seem like I'm able to push up PRs, it's probably best if you do it (but I'm keen on seeing how you do it after digging into the code in detail yesterday!)

[andrew-smartnews]

if you copy paste those two changes into the files as described, you should be able to reproduce easily - (or you can give me perms to push up a PR)

[sksamuel]

On github the way you do PRs for public projects is you fork the repo, push to your fork, and PR from fork to repo.
This avoids every project needing to give permissions to the public.
But I can just as easily do the work.

[andrew-smartnews]

oh - thanks for the tip - I'll try that out

[andrew-smartnews]

See PR: #342 @sksamuel

[sksamuel]

This now works in 2.6.0

ConfigLoaderBuilder.default().allowEmptySources....