How to pass --preview argument to black

[simgunz]

Hi,
in order to enable the experimental string processing of black, it is necessary to pass the --preview argument to black from the command line and apparently there is not a way to configure this behavior in black configuration file. How can I pass the --preview to black while using darker?

[akaihola]

Update: Design discussion (custom options vs. --extra-black-options) now in #589, and --extra-black-options implementation discussion in #351.

Arbitrary arguments to Black aren't yet supported.

Darker invokes Black directly through its internal Python API. The Black configuration is actually first read by Darker, and some options are passed on to Black. But --preview isn't currently one of those options.

We could either add --preview to the passed options, or add an --extra-black-options="--preview ..." kind of a command line argument to Darker.

What do you think of these options @simgunz?

[simgunz]

Thanks for the fast reply. I like it more the second one: --extra-black-options="--preview ..."

[akaihola]

@simgunz, this is now tracked in #351.

[akaihola]

#589 now proposes a --preview command line option.

I vote against adding corresponding configuration file options in the [tool.darker] section since the user can simply add

[tool.black]
preview = true

in the same file.

Discussion on the choice between --preview and something like --extra-black-options="--preview" is best continued in #589.