[BUG] Empty key in YAML sets value to null

[ddbtrmatic]

Describe the bug

Merging two YAML config files results in a null value if the last file has an empty key.

Example:

# default.yml

db:
  global:
    host: something
    options:
      useUTC: true

# development.yml

db:
  global:
    host: something_else
    # options key left blank
    options:

Result:

{
  db: {
    global: {
      host: 'something_else',
      options: null
    }
  }
}

Expected behavior
I would intuitively expect that the empty key is treated the same as an empty object in JSON and merged.

Please tell us about your environment:

• node-config version: 3.3.7
• node-version: 18.18.0

Other information

[lorenwest]

You would expect options to be an empty object? Why not an empty string? Or a numeric zero?

I guess the answer is - what does the YAML parser treat it as? My guess is it treats it as null, which is why your result ended up with null

[ddbtrmatic]

The confusion is caused by the fact that adding a value to the empty options changes the semantics of how node-config handles it, from a replacement to a merge. Someone familiar with the internals of YAML may figure this out, but a laymen could easily fall into this trap without understanding what's happening. The ambiguity of the YAML format itself leads to the confusion, so to your point, I don't expect a change.

However, it might be worth adding warning to the docs, similar to the warning that's already present about array replacement.