Properly check for valid argument Node in use-true-false rule

[bojand]

This fixes a crash in Atom using linter-xo that happens while typing on the opening bracket of t.truthy( or when closing on empty argument. This check makes sure the arg value is completely taken into account within the check before proceeding to check any of the || combinations. I was getting the crash in eslint-plugin-ava shipped with xo@0.14 which has different code than the master here; but I think the fix is still valid here.

[jfmengels]

Ah yes, that makes total sense.

Would you mind adding new test cases for this? testCase('t.truthy()') and testCase('t.falsy()'). You can put them in the valid section I'd say (speaking of which, maybe we should a have a rule saying that assertions should always have arguments?)

Thanks a lot @bojand!

[bojand]

Added tests. Should have checked and done it from start.

Yea that may be a good idea to have something like no-empty-arg rule. You do mean like a separate rule altogether correct, and nothing related to this PR? Or specifically within context of this rule? Are there valid scenarios perhaps where someone would want such usage? I can't really think of it but I don't know. If it's a separate rule I imagine that can be a different PR altogether, its kind of outside of the scope of this.

[jfmengels]

You do mean like a separate rule altogether correct, and nothing related to this PR?

Yes ;)

Are there valid scenarios perhaps where someone would want such usage?

Having an assertion without arguments? I don't think so no. Obviously there should be an exception for t.end(), t.pass() and t.fail(), but for the others, I don't see how it would be a valid use.

LGTM :)

[sindresorhus]

Yea that may be a good idea to have something like no-empty-arg rule.

Instead, how about a rule that ensures the argument length is correct for each assertion?

So t.pass() would be allowed, t.pass('msg') too, but not t.pass('msg, 'foo').

[sindresorhus]

Thank you @bojand :)

[jfmengels]

eslint/eslint#6023 :)