float is not parsed properly

[imagecmos]

my local version is 1.4.0
the case like this
YAML.parse("foo: !!float 3.0")
YAML.parse("foo: 3.0")
the result always is
{ foo: 3 }
the right result is not { foo: 3.0 }?

[eemeli]

Could you clarify how you think that the JS representation of the value 3.0 should differ from its representation of the value 3?

[imagecmos]

Could you clarify how you think that the JS representation of the value 3.0 should differ from its representation of the value 3?

we have a web page, users can edit their config then push it to target path
so we want the content of the config is the same as what users input

[eemeli]

The answer I was intending to give here was to use YAML.parseDocument() rather than YAML.parse(), but it turns out that the !!float tag is lost even then. That probably shouldn't happen. I'll test a bit more, and possibly tweak the number stringifier to keep the tag.

[eemeli]

Actually, I'll need to refactor the tag object a bit to accommodate this.

[eemeli]

With the most recent change, we get this:

const doc = YAML.parseDocument('foo: !!float 3.0') 
String(doc) === 'foo: !!float 3\n'

Effectively, I've made it so that explicit tags in the source correspond to explicit tags in the AST nodes, both when parsing as well as stringifying.

I'm considering what -- if anything -- to do about the .0 part. For instance, if you first parsed 3.0 as a float and then updated its value to 30, would you expect it to be stringified as 30 or as 30.0? Similarly, if you parsed 3.10 and updated its value to 30, how should that be stringified?

[eemeli]

Closing this as fixed. When a non-scientific float is now parsed, if its value has 0 as the last fraction digit, it sets a property minFractionDigits for the resolved node, which is then used during stringification. So if you update a value that was parsed from 3.0 to 30, it'll be stringified as 30.0:

const doc = YAML.parseDocument('foo: !!float 3.0\nbar: 4.20e3')
// In order to keep the explicit tag & minFractionDigits we need to fetch and
// modify the original node, rather than using set() to overwrite its value.
const float = doc.get('foo', true)
float.value = 30
String(doc)
// foo: !!float 30.0
// bar: 4.2e+3

Setting minFractionDigits on a scalar node with a Number value will control the string output, provided that its format is empty and its tag is either empty, or set to 'tag:yaml.org,2002:float'.

Exponential values now keep that form, but their fraction digits aren't remembered. This is due to needing to use Number#toExponential() to stringify them, as Intl.NumberFormat doesn't yet support them.