Update dev dependency "prettier"

[mikeharder]

Overview

I tried updating to prettier@^2.0.5 (draft PR #9325), but when I execute npm run format, there are a ton of formatting changes. Examples include:

• Spaces are added after the word "function" in function expressions
  • https://prettier.io/blog/2020/03/21/2.0.0.html#always-add-a-space-after-the-function-keyword-3903httpsgithubcomprettierprettierpull3903-by-j-f1httpsgithubcomj-f1-josephfrazierhttpsgithubcomjosephfrazier-sosukesuzukihttpsgithubcomsosukesuzuki-thorn0httpsgithubcomthorn0-7516httpsgithubcomprettierprettierpull7516-by-bakkothttpsgithubcombakkot
• Different indentation of multi-line expressions

In order to upgrade, I think we will need to either modify our config to make prettier@2 work more closely to prettier@1, or we will need to reformat nearly all our source files.

Breaking Changes

https://prettier.io/blog/2020/03/21/2.0.0.html#breaking-changes

Relevant breaking changes:

• Drop support for Node versions older than 10
  • Probably OK since we only build on Node 10 and above. Node 8 is only used for testing.
• Change default value for trailingComma to es5
  • Might be relevant since value is not set in https://github.com/Azure/azure-sdk-for-js/blob/master/sdk/.prettierrc.json, but we can always set a different value if we don't like the new default.
• Change default value for arrowParens to always
  • Already set to this value in our config
• Change default value for endOfLine to lf
  • Already set to this value in our config

[willmtemple]

@mikeharder It looks like this upgrade is required to support import type statements (and any other new additional syntax that shows up, I imagine). This seems more important now, given that we are running prettier on all of our staged files for commit, so if I use something that has import type, I'm now seeing the commit hook fail.

CC @xirzec @ramya-rao-a @deyaaeldeen

Don't want to speak for everyone, but personally I'm okay with reformatting our source files to take the upgrade to prettier 2.

[xirzec]

I also would like to move to prettier2. I don't mind trailingComma being es5, I think it's easier on diffs.

[witemple-msft]

Note this is also blocking usage of ES private fields: #15826 (comment)

[ramya-rao-a]

Drop support for Node versions older than 10

We dropped support for Node.js 10 this month, so we are good to go here

[JonathanCrd]

Hi, to confirm, we are fine with reformatting our code to prettier 2?

I am considering the option of splitting this task into 2 or more PRs, one for updating the dependency version in the package.json files, and another one just for the output of npm run format in all the packages, since there will be tons of modified files. I'm curious about what you think about this.

[deyaaeldeen]

@JonathanCrd yes we're would like to reformat, but I guess we will need to agree on which configuration to use. We use these configs currently but v2 changes some defaults which affects the behavior of the configs not listed in our config file.

[maorleger]

Hi, to confirm, we are fine with reformatting our code to prettier 2?

I am considering the option of splitting this task into 2 or more PRs, one for updating the dependency version in the package.json files, and another one just for the output of npm run format in all the packages, since there will be tons of modified files. I'm curious about what you think about this.

Would that cause your first PR to fail because the check:format command will start failing?

Vote YES for trailing commas this November! 😄

[JonathanCrd]

Would that cause your first PR to fail because the check:format command will start failing?

@maorleger I didn't consider that, thanks for pointing it out. I'm going to open a draft pr to test it.

[JonathanCrd]

All "prettier" dependencies in the repo have been upgraded to Prettier 2 (^2.5.1)