Black: Don't use subscription brackets to break long lines?

[yurkobb]

Consider this input:

class Test:
    def method(self):
        ctx = super().get_context_data(**kwargs)
        ctx["shipping_methods"] = list(
            ShippingMethod.objects.all().values("id", "labels__identifier")
        )
        ctx["shipping_method_fields"] = (
            MyCheckoutForm.Meta.shipping_required_fields
        )
        return ctx

And output:

class Test:
    def method(self):
        ctx = super().get_context_data(**kwargs)
        ctx["shipping_methods"] = list(
            ShippingMethod.objects.all().values("id", "labels__identifier")
        )
        ctx[
            "shipping_method_fields"
        ] = MyCheckoutForm.Meta.shipping_required_fields
        return ctx

I would (subjectively) expect the third assignment to stay the way it was.

Do "a[...]" often contain more than 1 element between the brackets? (Ignore this argument please; of course they do if it's something other than a string literal)

---

Operating system:
Python version: 3.7.3
Black version: 19.3b0
Does also happen on master: yes

[JelleZijlstra]

I agree that this looks pretty weird. If we can find a way to fix this issue without affecting other existing formatting too much, I'd be supportive of changing it.

[zsol]

IMO the reason this looks weird is because the line break is on the LHS of an assignment statement and the indented line has a single, trivial expression.

(
    shipping_method_fields
) = MyCheckoutForm.Meta.shipping_required_fields

Looks the same kind of weird to me.

[alexanderGerbik]

Breaking lines on subscription brackets is quite confusing, it makes it look like list literal (I don't know the better way of formatting this though):

        return self.client.post(url_for("auth.obtain_token"), json=credentials).json[
            "token"
        ]

I think the same formatting can be observed in the following issues - #500 #1048

[yurkobb]

Maybe something like this?

        return (
            self.client.post(url_for("auth.obtain_token"), json=credentials)
            .json["token"]
        )

[remytms]

I would even propose :

        return (
            self.client
            .post(url_for("auth.obtain_token"), json=credentials)
            .json["token"]
        )

Following the same rule as parameters of a function. If it fits on one line keep it on one line. If not, split in multiline. Here instead of splitting on commas, it splits on dots.

[ttilberg]

I found this issue while trying to find community comments on code that I wondered "Is this formatting intentional? Is this a bug? Should I train myself to accept this?"

Here is the example I was reviewing:

# ...
                yield {
                    # ...
                    "isAvailable": result["stock"]["relativeInventoryForSets"][
                        "isAvailable"
                    ],
                    "appointmentLeadTimeDays": result["stock"][
                        "appointmentLeadTimeDays"
                    ],
                    "stockLevel": result["stock"]["stockLevel"],
                    "zip_code": response.meta["item"]["zip_code"],
                }

It gets weirder if there's even longer keys to dig into:

                {   # ...
                    "isAvailable": result["stock"]["relativeInventoryForSets"][
                        "isAvailable"
                    ]["isLong"]["isQuiteLong"],
                }

In this specific case, refactoring to a local stock, or moving some extraction code directly to an instance method could probably improve the situation, but I wanted to bring this example to the table for debate and potential refinement. I think it's reasonable to dig into JSON keys, and I think the way it gets formatted if the json keys are long is hard to interpret.