When long, single-line strings (i.e. does not contain "\n") are marshalled, the yaml emitter seems to force line breaks at 80 characters, but does so without prefixing the string with the multi-line notation (e.g. ">" or "|"). This results in unusable yaml output like in the example below.

Example:

data := yaml.MapSlice{{"test", "abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd"}}

res, _ := yaml.Marshal(data)
fmt.Println(string(res))

Output:

test: abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd
  abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd

As a workaround, simply appending "\n" to the end of a string that's known to be lengthy works fine, although not ideal since the yaml output now exceeds the 80 char width. Mutiline ">" prefixed outputs would be preferable.

Output with trailing \n:

test: |
  abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd aabdasfadsfdasfadsfasd abdasfadsfdasfadsfasd abdasfadsfdasfadsfasd

Appreciate if someone could confirm whether this is an issue or just incorrect usage. If a fix is needed, I'd be happy to work on a PR. Thanks!