Re: Next YAML: drop equality definition

Oren,

> Actually, I don't see how a YAML library can _unintentionally_
> discard identities of scalar nodes with custom tags. Could you
> show an example?

I found an example by myself.

A YAML document,

- &A 3.141592653589793238462
- *A

is usually loaded as

[!float 3.141592653589793238462, !float 3.141592653589793238462]

in many YAML systems. Here, the identity of &A is lost.

The problem is, this document can mean

- &A !not_float 3.141592653589793238462
- *A

by an implicit tag resolution with some customized schema.

If a schema-blind tool loads the document and save as

[3.141592653589793238462, 3.141592653589793238462]

and !not_float requires identity preservation, the document
is broken.

I see what is unsafe to store some data that needs identity
preservation into a YAML scalar.


As far as we only have this example, the remaining issue
is how much we expect for schema-blind tools.

If a schema-blind tool load and save the document like
above, the user will not be happy anyway, even if the
node is indeed of !float. If the document is written
with anchors and aliases, the user will not want any
schema-blind third-party YAML tools to destroy the
identity anyway.


Another point is, if a schema-blind tool loads the value
as !float and save it as

- 3.14159265359
- 3.14159265359

the document is also broken. Note that the trailing digits
are rounded due to the limited precision of native float
type.

If a schema-blind tool loads and saves a YAML document,
there are so many unsafeties besides scalar's identity.
So, we should try to solve all unsafeties of such use
cases.


I appreciate your comments.

Osamu Takeuchi


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