Formatting with visual selection doesn't respect indentation

[davidsu]

It formats nicely but removes indentation from first line of visual selection.
I suppose it would be more reasonable to just keep the current indentation

[davidsu]

I've made a pull request for this #78

[mitermayer]

Fix this on branch 1.x (ec6ede9)

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Important notes:
Using the prettier api for --range-start and --range-end had some downsides:

• sending larger buffer to prettier
• requires the whole file to be valid even when formatting just portion of the file.

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Details:
I kept the old behaviour as the default, but made it configurable via a flag, so users can make partial formatting enabled for them if they wish by simply:

let g:prettier#partial_format=1

I also created 2 helper commands :PrettierPartial and :PrettierFragment

• :PrettierPartial - is the intended behaviour of Respect indentation for visually selected ":Prettier" #78 and Formatting with visual selection doesn't respect indentation #75 (sends the whole buffer to prettier and uses --range-start and --range-end to control formatting, it can fail if the file has errors even if outside the supplied range)
• :PrettierFragment - is the previous default behaviour where we only send selected portion to prettier (it has some benefits in that we only send less buffer and allow for formatting sections of files that are not entirely valid as a whole and have errors)

[mitermayer]

cc @docwhat,