Validate input of Q.all

[foretspaisibles]

When it called with something else than an array of promises, the static method Q.all should fail with a TypeError error condition.

A common pitfall when using the library is to call Q.all on an array filled with return values of Q.defer() instead of the promise member of these values.

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It might also be argued that Q.all should return a failed promise, but it seems to me that an exception is more appropriate for what seems like a program logic error.

[vingiarrusso]

@michipili Check out the conversation on my pull request #667. You have a handful of failing tests with this change (#701), due to strictly checking for an array as the parameter. Its kind of a weird situation where you know you want an array but even the library itself passes .all() an array-like (see promised decorator fn).

[foretspaisibles]

@vingiarrusso I see, I overlooked that CONTRIBUTE.md file. The main contribution in my branch is the use of isPromise to validate items of the array-like arguments, maybe you would like to build this in your own branch? The call would then be

Array.prototype.every.call(arrraylike, isPromise)

instead of

truearray.every(isPromise)

In the code, there is a validation which does not happen on each execution paths, this should be fixed.

Refs: https://github.com/michipili/q/commit/9518c0588469522007d26f5d2ae62fb080c1b536#diff-a148bc52a39c990d02038097d8177455R1564

[cefn]

Can I request also that there is a useful failure condition when calling Q.all with 'promises' with the value undefined.

Q.all([void(0)])

I recently suffered for several days from this bug as Q.all was silently resolving when I did this...

                    return Q.all(keys.map(function(key){
                            tree.syncRecursive(getChildTopic(topic, key));
                        }))
                        .then(function(){
                            return tree.getItem(topic);
                        })

...instead of this...

                    return Q.all(keys.map(function(key){
                            return tree.syncRecursive(getChildTopic(topic, key));
                        }))
                        .then(function(){
                            return tree.getItem(topic);
                        })

Spot the difference ;)