Format or write R objects as YAML 1.2.

format_yaml() returns YAML as a character string. write_yaml() writes a YAML stream to a file or stdout and starts every document with a document start (---) marker. Both functions honor a yaml_tag attribute on values (see examples).

Long single-line strings and multiline strings containing unindented, single-line paragraphs separated by exactly one blank line are automatically wrapped when a line would be wider than width columns and has a safe word boundary. Wrapped strings use a YAML folded block scalar: >- preserves no final newline, while > preserves exactly one. Paragraph breaks and all other string content round-trip through parse_yaml() unchanged. Strings that cannot be folded losslessly use a literal or quoted representation, and mapping keys are never wrapped.

Literal blocks use explicit indentation indicators when needed to preserve leading spaces or tabs. They keep physical blank lines empty and preserve later-indented lines.

Usage

format_yaml(value, multi = FALSE, width = 80L)

write_yaml(value, path = NULL, multi = FALSE, append = FALSE, width = 80L)

Arguments

value

Any R object composed of lists, atomic vectors, and scalars.

multi

When TRUE, treat value as a list of YAML documents and encode a stream.

width

Target maximum line width in columns. Long single-line strings and unindented paragraphs with safe word boundaries are wrapped. Individual lines may still exceed width when there is no safe break point (e.g. a single long word) or under deep indentation. Use NULL or Inf to disable wrapping.

path

Scalar string file path to write YAML to when using write_yaml(). Tilde prefixes (~) are expanded as by base::path.expand(). When NULL (the default), write to R's standard output connection.

append

When TRUE, append to path instead of replacing it. Defaults to FALSE.

Value

format_yaml() returns a scalar character string containing YAML. write_yaml() invisibly returns value.

Examples

cat(format_yaml(list(foo = 1, bar = list(TRUE, NA))))
#> foo: 1.0
#> bar:
#>   - true
#>   - ~

docs <- list("first", "second")
cat(format_yaml(docs, multi = TRUE))
#> ---
#> first
#> ---
#> second

tagged <- structure("1 + 1", yaml_tag = "!expr")
cat(tagged_yaml <- format_yaml(tagged), "\n")
#> !expr 1 + 1 

dput(parse_yaml(tagged_yaml))
#> structure("1 + 1", yaml_tag = "!expr")


write_yaml(list(foo = 1, bar = list(2, "baz")))
#> ---
#> foo: 1.0
#> bar:
#>   - 2.0
#>   - baz

write_yaml(list("foo", "bar"), multi = TRUE)
#> ---
#> foo
#> ---
#> bar

tagged <- structure("1 + 1", yaml_tag = "!expr")
write_yaml(tagged)
#> ---
#> !expr 1 + 1