What does a single exclamation mark do in YAML?
That !
is the non-specific tag.
The YAML specification 1.2 (as well as the previous 1.1) says that :
By explicitly specifying a “!” non-specific tag property, the node would then be resolved to a “vanilla” sequence, mapping, or string, according to its kind.
Take a look here to the tag "grammar":
none : Unspecified tag (automatically resolved by application). '!' : Non-specific tag (by default, "!!map"/"!!seq"/"!!str"). '!foo' : Primary (by convention, means a local "!foo" tag). '!!foo' : Secondary (by convention, means "tag:yaml.org,2002:foo"). '!h!foo': Requires "%TAG !h! <prefix>" (and then means "<prefix>foo"). '!<foo>': Verbatim tag (always means "foo").
Why is YamlDotNet throwing a error? I can't be 100% sure, but I think you found a bug.
YamlDotNet is a port of LibYAML, so it's easy to compare sources.
Line 2635 of scanner.c (LibYAML):
/* Check if the tag is non-empty. */
if (!length) {
Line 2146 of Scanner.cs (YamlDotNet ):
// Check if the tag is non-empty.
if (tag.Length == 0)
I know, both looks very similar, but at this point length
is 1 and tag.Length
is 0. Original C code takes care of the initial "!" (whole length) but C# doesn't do it (just the tag "name" length).
File an issue to the project.