More RFC 8259 nits

[hildjj]

Rule details

Check as many of the constraints from RFC 8259 marked "interoperable in the sense"

What type of rule is this?

Warns about a potential problem

Example code

- Invalid top-level: `"foo"`
- Outside float64 (will parse as 0): `[1e-325]`
- Subnormal warning: `[4.94e-324]` 
- Too-large integer: `[18014398509481985]`
- Duplicate key (just needs a test): `{"a\\b": 0, "a\u005Cb": 1}`

Participation

• I am willing to submit a pull request to implement this rule.

Additional comments

RFC 8259 marks several potential interoperability issues with "interoperable in the sense":

• Only an object or array at the top level. This is the most controversial of these.
• Unique keys (already handled by no-duplicate-keys)
• Not order-dependent (not lintable, unless we wanted there to be another rule that enforced order, I suppose)
• (Implied in 8259) Floats should fit into a double. Support for sub-normals should likely be optional.
• Integers in the range in the range [-(253)+1, (253)-1]. Note that no-unsafe-values currently will not catch integers outside that range that have not gotten all the way to being +/-Infinity.
• Valid Unicode. no-unsafe-values catches this now.
• No duplicate keys, including ones that differ by only Unicode escapes. no-duplicate-keys only needs some tests added to check that "a\b" and "a\u005Cb" are duplicates.

[nzakas]

Thanks for the feedback. I'm unclear on what it is you're suggesting. Are you saying we should update some existing rules, create new rules, etc.? Can you be more specific?

[nzakas]

Also, can you please add a link to the RFC for easy reference?

[hildjj]

RFC8259 is the current IETF description of JSON. It is aligned with ECMA-404, but focuses more on interoperability between systems rather than on how JSON.parse is implemented in ECMAscript/JavaScript.

Here are more explicit recommendations:

• new rule: top-level-composite, which checks that the top-level thing in a JSON file is either an object or an array. This might be off in the default config.
• no-unsafe-values should check for integers out of range, floats out of range, and warn on subnormals (by default).
• Add a test for escaped characters in no-duplicate-keys.test.js

Sorry I wasn't more clear before.

[nzakas]

Got it, thanks. These all seem like good additions to me.

Only question is the naming of top-level-composite, as I'm not sure it communicates the intent. Maybe interopable-top-level instead?

[hildjj]

interopable-top-level works fine for me. Would you like me to put together a PR?

[nzakas]

Or maybe top-level-interop is better? (Shorter, maybe more readable?)

And yes, but if you could please do a separate PR for each task, it would be appreciated.

[hildjj]

I'm making progress on a PR.

What do we think about -0?
Safe for interop?

[hildjj]

Those three PRs should cover this issue.

[nzakas]

What do we think about -0?
Safe for interop?

Good question. It's definitely not a problem in JavaScript, but I'm unsure of other languages.

[hildjj]

What do we think about -0?
Safe for interop?

Good question. It's definitely not a problem in JavaScript, but I'm unsure of other languages.

Let's leave it be then. 8259 doesn't say anything about it, so it's a separate issue if we decide it needs to be added.