parseYaml inserts null when document stream starts with a comment

[0xd3e]

I just found out that a null value is added to the array when I parse a stream of YAML documents that starts with a comment.

YAML

# Test
---
foo: bar
---
baz: cuux

Jsonnet

std.parseYaml(importstr 'test.yaml')

Result

[
   null,
   {
      "foo": "bar"
   },
   {
      "baz": "cuux"
   }
]

Expected Result

[
   {
      "foo": "bar"
   },
   {
      "baz": "cuux"
   }
]

Current Workaround

std.prune(std.parseYaml(importstr 'test.yaml'))

[johnbartholomew]

Yeah, unfortunately go-jsonnet has a few problems with YAML document streams. The YAML parsing library that we currently use doesn't support streams (I think? I need to check newer versions), so we have some extremely basic stream-splitting code in go-jsonnet and then parse each document separately. But that stream-splitting code doesn't really implement the spec, it really just splits on lines that start with "---", so it does not properly cope with directives/frontmatter sections.