prefer-lodash-typecheck does not catch typeof configuration[name] === 'undefined' about eslint-plugin-lodash HOT 11 CLOSED

See #5 for explanation.

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@mik01aj The example that you have provided has an extremely limited use case: it is only relevant when checking for variables in the inherited scope (globals, such as in the context of browser scripts).

Fair to say that the default behaviour should be to enforce the use of _.isUndefined through ESLint rules and use /* eslint-disable lodash3/prefer-lodash-typecheck */ in such very specific cases.

You will never get such an error when the variable declaration is present, e.g. when checking function parameter presence.

(a) => {
    // Does not produce an error.
    _.isUndefined(a);
};

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Agreed. 👍

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@ganimomer any input?

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The intent of the rule is to prefer Lodash versions of type checking, as long as they have the exact same meaning and behavior in all cases.
In the case of _.isUndefined, it is not the exact same is typeof(a) === 'undefined'.
I suppose the rule could use the context to check if either the expression is a variable that exists or isn't a variable (i.e., typeof a.b === 'undefined' or a => typeof(a) === 'undefined')
but the rule definitely shouldn't have 'false positives' like you're suggesting, where the replacement shouldn't happen and the rule should be turned off.
We could get around to implementing that soon, or anyone could submit a PR if you like.

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I think that this could be configurable, so that the rule wouldn't warn about typechecks with undefined by default, but you could have a alsoForUndefined flag that would enable this.

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I don't agree.
Under no configuration should any rule ever report in a case where fixing it would cause an error.
However, like I said, it can only report typeof <expression> === 'undefined' where fixing is possible.
ESLint enables rules to check which variables are declared with context.getDeclaredVariables()

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@ganimomer so how about triggering a warning only when using it as typeof <declared-variable> === 'undefined'? In this case, lodash typecheck is equivalent.

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That's the idea. :)
Well, that and checking any expression that isn't a literal.
technically typeof a.b === 'undefined' will behave the same way as _.isUndefined(a.b).
v0.4.0 we released yesterday fixed that part, but still hasn't fixed the part where it's a declared literal, since that's a bit more complicated.

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Great, thanks! 👍 I'm looking forward to more good news! :)

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Technically, this issue is resolved. I'm closing it and opening a separate issue for typeof <declared-variable>.

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