eslint-plugin-no-closure v1.0.1

No Closures

An eslint plugin to prevent unwanted function closures.

Usage

To use this plugin, first install it

yarn add -D eslint-plugin-no-closure

Then add it to your eslintrc

{
  ...,
  "plugins": [ ..., "no-closure" ],
  "rules": {
    ...,
    "no-closure/no-tagged-closures": "error"
  }
}

disallow closing around variables for tagged functions (no-tagged-closures)

Sometimes you want to prevent a function from referencing variables outside of its scope. Since this is allowed in javascript it's not possible to outright ban, but this rule will report where this is happening for tagged functions.

Rule Details

This rule disallows closures in functions that are tagged. A tagged function must have a comment that starts with eslint-no-closure immediately before the function, or as a line comment on the line immediately preceeding it.

Options

By default, the rule will report the declarations of variables that are closed in tagged function, tagged functions that cose any variables, and any references to closed variables within tagged functions. Since this produces up to three reports for a single violation, each class of reports can be independently disabled.

• declaration set to "never" to not report the declaration of variables that are closed (Default "always").
• function set to "never" to not report tagged functions that close variables (Defalt "always").
• reference set to "never" to not report references to closed variables in tagged functions (Default "always").

Examples

Examples of incorrect code for this rule:

/*eslint no-closure/no-tagged-closures: "error"*/

const x = 5;
// eslint-no-closure
function foo() {
  void x;
}

Examples of correct code for this rule:

/*eslint no-closure/no-tagged-closures: "error"*/

const x = 5;
function foo() {
  void x;
}

/*eslint no-closure/no-tagged-closures: "error"*/

// eslint-no-closure
function bar() {
  const x = 5;
  function foo() {
    void x;
  }
}

/*eslint no-closure/no-tagged-closures: "error"*/

type X = number;
// eslint-no-closure
function foo() {
  const x: X = 5;
}

When Not To Use It

This rule only checks functions that are tagged, so there's little harm in using it. However, this current doesn't support selective closures, so this rule won't work if you want to verify that you only close a set of specific variables.