johnstonbl01 / eslint-no-inferred-method-name Goto Github PK

[Edit: clarified and adjusted tone of my wording]

"Every form of function expression assignment in ES6 infers a name that can be used inside the function for recursion."

That statement is false. The function name inference has nothing to do with the ability to make lexical name recursive calls. The inference is assigning a name property to the function object, not giving the function object a named binding in the surrounding (or owned) lexical environment (which would be required for recursion).

The code snippet also reinforces this incorrect information:

return foo(f, i); // foo is inferred within the compact object literal

That foo(f,i) call will be an error, as there will not be a foo lexical identifier referencing the function. There is no such thing as inferring a lexical name. The foo lexical name will exist at that line of code, but it'll be pointing to the foo object (not function) declared on the first line of the snippet. As such, a TypeError will be thrown because you're trying to call a non-function value.

Concise methods do not have lexical name bindings and thus such a lexical name cannot be used, being that it doesn't exist, for recursion or any other self-referential purpose.

The following line:

myPromise.then(doSomething)

Generates the following error in ESLint:

[Error - 11:23:34 AM] ESLint stack trace: [Error - 11:23:34 AM] TypeError: Cannot read property 'type' of null Occurred while linting /myapp/script.js:2 at /myapp/node_modules/eslint-plugin-no-inferred-method-name/lib/rules/no-inferred-method-name.js:40:51 at Array.forEach (<anonymous>) at Program:exit (/myapp/node_modules/eslint-plugin-no-inferred-method-name/lib/rules/no-inferred-method-name.js:37:29) at /myapp/node_modules/eslint/lib/linter/safe-emitter.js:45:58 at Array.forEach (<anonymous>) at Object.emit (/myapp/node_modules/eslint/lib/linter/safe-emitter.js:45:38) at NodeEventGenerator.applySelector (/myapp/node_modules/eslint/lib/linter/node-event-generator.js:254:26) at NodeEventGenerator.applySelectors (/myapp/node_modules/eslint/lib/linter/node-event-generator.js:283:22) at NodeEventGenerator.leaveNode (/myapp/node_modules/eslint/lib/linter/node-event-generator.js:306:14) at CodePathAnalyzer.leaveNode (/myapp/node_modules/eslint/lib/linter/code-path-analysis/code-path-analyzer.js:655:23)

The real issue is with compact object literals. Here's the example we need to fix:

const repeater = {
  name: 'Repeater',
  types: [
    { f: 'function' },
    { n: 'number' }
  ],
  repeat (f, n) {
    let i = n - 1;

    if (typeof f === 'function') {
      f();
    } else {
      throw new Error('repeat: A Function is required.');
    }
    if (!n) {
      return undefined;
    }

    return repeat(f, i);
  }
};

repeater.repeat(() => {console.log('foo');}, 10);

Results:

foo
ReferenceError: repeat is not defined

The way to fix that is to report an error when the method name is used within the function, because inside the function, the method name is undefined. The error should be reported for this line:

    return repeat(f, i);

The built-in no-undef rule already catches this error, but we need to explicitly tell the user that compact method names are not available inside the method in order to clear up any confusion.

I'm trying to get this plugin working, but I can't. I've created a repo with only the readme's example and configuration, but still no luck.

Minimal reproduction case:

https://github.com/ferhtgoldaraz/issue-eslint-no-inferred-method-name

If I do:

❯ $(npm bin)/eslint index.js

I get no warnings, no errors, no nothing.

Is it possible to install this rule as an eslint plugin so you don't have to copy the file into the rules directory? That would significantly enhance the install experience.