feature suggestion: must use value

[lukeapage]

so we require explicit chains, but I don't like the look of..

_.chain(a)
    .map('a')
    .forEach((a) => {})
    .value();

I think the code would be clearer and more likely correct if any chains ending in value() are assigned to something, so the above code would have to be

var description = _.chain(a)
    .map('a')
    .value();
_.forEach(description, (a) => {})

and it would prevent chains not being assigned (e.g. useless code)

wdyt?

btw sorry I know I haven't submitted a pr for my last feature but still slowly switching on your rules on our large codebase...

[ganimomer]

Well, since Lodash v4, forEach and its kind all end implicit chaining, so you could technically write

_(a)
    .map('a')
    .forEach((a) => {})   

Which would make this redundant. If you use the chain-style with as-needed, it would warn against this, and then no-double-unwrap would warn against the extra .value().

Also, this would assume that everyone uses each function for its intended use.
I've seen people use map, filter and especially some for side effects, and in some cases it's too hard for the plugin or Eslint itself to check for that.

[lukeapage]

Yes, im aware we could use implicit chaining but i was outvoted, other developers preferred consistency/simplicity over elegance.
A better description might be "avoidCallsOnlyForSideEffects" with an ignore option or somesuch defaulting to forEach.. i guess that doesnt really address my forEach chain issue unless i make the ignores more specific but it does address my side-effects concern.

[lukeapage]

And it would be easy to tell if lodash was used only for side effects (basically determine if the parent is a statement), just difficult to tell if it was used for value and side effects (but again possibleb

[captbaritone]

Possibly related, I've been thinking that there should be a rule about requiring that the output of _.each does not get used, and another that the output of other collection methods DO get used.

This would help prevent people using _.map for side effects only.

[lukeapage]

Yes, that would be good.

[ganimomer]

You make a good point - the whole point of giving options to rules like chain-style is not to make assumptions like I just made.
I'd say something like collection-method-value would work.

[lukeapage]

Good rule, it found 4 cases of confusing code. I am wondering if for my other concern, which is purely stylistic, another rule "disallow-chain-methods"(with option for methods to not allow chaining with) might make sense so I could disallow forEach within a chain ?