consistent-optional-props

ESLint plugin / consistent-optional-props

Ensures consistent optional property style:

• Combined syntax: “x?: T | undefined”
• Only optional syntax: “x?: T”
• Only undefined syntax: “x: T | undefined”

module.exports = {
  plugins: ["misc"],
  rules: {
    "misc/consistent-optional-props": [
      "error",
      {
        classes: "combined" | "optional" | "undefined",
        interfaces: "combined" | "optional" | "undefined",
        overrides: [
          {
            _id: string,
            filesToLint: string[],
            filesToSkip: string[],
            pattern: string | string[],
            propertyPattern: string | string[],
            style: "combined" | "optional" | "undefined",
            target: "classes" | "interfaces"
          },
          ...
        ]
      }
    ]
  }
};

| Option | Description | Default | | :—– | :———- | :—— |

classes	Preferred style for classes	"undefined"
interfaces	Preferred style for interfaces	"optional"
overrides._id	Id	-
overrides.filesToLint	Files to lint (minimatch patterns)	[]
overrides.filesToSkip	Files to skip (minimatch patterns)	[]
overrides.pattern	Only for selected class/interface names (regular expression)	[]
overrides.propertyPattern	Only for selected property names (regular expression)	[]
overrides.style	Preferred style	-
overrides.target	Classes or interfaces	-

Examples of incorrect code

interface I {
  x?: string;
  y: string | undefined;
}

Examples of correct code

interface I {
  x?: string | undefined;
  y?: string | undefined;
}