no-useless-return and no-empty conflict

Tell us about your environment

• ESLint Version: 5.6.1
• Node Version: 10.11.0
• npm Version: 6.4.1

What parser (default, Babel-ESLint, etc.) are you using? default Please show your full configuration: My configuration is insanely elaborate covering most of the rules in depth, for an easy to verify example use this

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint. See the demo for a live example of source code that causes this issue, try clearing line 3.

eslint . --ext .js

What did you expect to happen? One of the two wouldn’t error, in order to avoid conflict which each other. Even --fix conflicts with these rules. What actually happened? Please include the actual, raw output from ESLint. without --fix

../src/utility/LibraryHandler.js
  65:11  error  Unnecessary return statement  no-useless-return

with --fix

../src/utility/LibraryHandler.js
  64:46  error  Empty block statement  no-empty

[not-an-aardvark]

To clarify, if code after the if/else statement isn’t supposed to be executed, then using return is fine (and no-useless-return won’t report an error if there are additional statements).

Even if there aren’t additional statements after the if/else, if the first case is conceptually supposed to be an “early exit” it might be clearer to write it this way:

function func(bool, num) {
	if(bool) {
		return;
	}

        if(num === 5) {
		console.log("yay");
	} else if(num > 0) {
		console.log("rip");
	}
}

If the first case isn’t conceptually an “early exit” and return is being used as a placeholder for “do nothing”, then it seems clearer to actually do nothing (perhaps with a comment clarifying this choice), otherwise the use of return could be misleading to people reading/modifying the code in the future.

[not-an-aardvark]

@LJNeon The reasoning for adding a comment is that it can help explain to readers of your code why the block is empty, when it might otherwise appear that it was a mistake. For example, you could write something like this:

function func(bool, num) {
	if(bool) {
		// do nothing
	} else if(num === 5) {
		console.log("yay");
	} else if(num > 0) {
		console.log("rip");
	}
}

In other words, adding a comment to the block is less of a workaround to appease the linter, and more of a mechanism for making sure your code is readable. Using return; in this case isn’t ideal because it could cause unexpected results if you need to add additional statements after the if/else statement (namely, those statements will be skipped).