Key `n` is mapped to `FALSE` in simple example

[ramiromagno]

{yaml} package version is 2.3.6.

library(yaml)

x <- "
n: 100
"
  yaml.load(x)
#> $`FALSE`
#> [1] 100

[ramiromagno]

Okay, I just realised there are some special values in YAML. n stands for "not", is it? It seems that quoting it works as I expected. Is that the way to escape its special meaning?

I'd prefer to not force the user to quote the data in the YAML file. I can I somehow tell yaml.load_file() to treat n literally?

[spgarbet]

This is a quirk of yaml 1.1. It's removed for yaml 1.2, but efforts to get that up and going aren't going so fast.

[spgarbet]

It might be possible to write a custom boolean handler. I've not tried that.

The parser returns a "bool#yes" and "bool#no" for these tag types. It might be possible to modify this behavior.

Try writing a custom handler and post your code here. If that works, I'll see if it can become an option to ignore in the parser output.

[spgarbet]

This seems to work:

yaml.load("'n': false\ntrue: 200", 
                handlers=list(boolean=
                    function(x) if(x %in% c('n','y')) x else tolower(x)=='true'))

[ramiromagno]

Thanks for your answers. But it seems that only works because the input has n quoted, i.e. 'n'.

[spgarbet]

That slipped through in my example. I just tried it and upstream it's emitted a T/F for this, so I don't see an easy way. It'll require compiler modification.

[ramiromagno]

Okay, thanks for trying. I'll leave this issue open, but feel free to close it if you think this functionality is unlikely to be supported.

[spgarbet]

It is the plurality of issues opened. The other being requests for yaml 1.2 (which doesn't have the n/y issue). I've started an experiment to use the libfyaml library and see if it solves both problems.

[r2evans]

Related on SO, for the record (if it helps): https://stackoverflow.com/questions/75595253/rmarkdownyaml-front-matter-converts-some-parameter-names-to-true

[jl5000]

Ah, this must be why I'm getting this problem:

tmp <- tempfile(fileext = "yaml")
writeLines("x: foo\ny: bar", tmp)
yaml::read_yaml(tmp, readLines.warn = FALSE)
#> $x
#> [1] "foo"
#> 
#> $`TRUE`
#> [1] "bar"

^{Created on 2025-08-13 with reprex v2.1.1}

Some warning about the use of these special values would be helpful on import.