json/no-unsafe-values

JSON puts no limit on how large or how precise a number is, but most programs read numbers into 64-bit floats. A number that doesn't fit silently changes when the file is read. This rule reports:

• a number that's too large and becomes Infinity
• a number that's too small and becomes 0
• an integer outside the safe range, above 9007199254740991 or below -9007199254740991, which may be rounded to a nearby integer
• a subnormal number, which has fewer digits of precision than it's written with
• a string with a lone surrogate, which can't be encoded as UTF-8

Configure

Off by default. It needs an ESLint config that says which files are in the language:

import json from "@eslint/json";

export default [
  {
    files: ["**/*.json"],
    plugins: { json },
    language: "json/json",
    rules: { "json/no-unsafe-values": "error" },
  },
];

It also works with json/jsonc and json/json5.

Examples

Reported:

{
  "large": 1e400,
  "small": 1e-400,
  "id": 9007199254740993,
  "subnormal": 2.2250738585072009e-308
}

{
  "emoji": "\ud83d"
}

Not reported:

{
  "large": 1e300,
  "zero": 0.0,
  "id": "9007199254740993",
  "emoji": "\ud83d\ude00"
}