[Typescript] Improvment for arrowParens rule

I’m opening this issue here as I believe it makes the most sense.

Basically I got a situation where I cannot get a combination to suit simultaneously both prettier and tslint rules.

Environments:

• Prettier Version: 1.16.4
• Running Prettier via: vscode
• Runtime: node 10.13.0
• Operating System: ubuntu

Steps to reproduce:

On a typescript based project, define a method such as:

const MockedRollbar = { error: err => { console.log('mocked rollbar error call', err) }, warn: err => { console.log('mocked rollbar warn call', err) }, }

the tslint.json has the following options:

"arrow-parens": false, or "arrow-parens": true, or “arrow-parens”: [true, “ban-single-arg-parens”]

Latter would be ideal as it would check for parentheses except for single argument parameters

However at .prettierrc I got just two options

“arrowParens”: “avoid | always”,

I cannot figure a way to use both plugins in a way that auto-formatting keep the tslint rules valid.

Expected behavior:

Provide more granular options to prettier so that one is not forced to wrap every single function with parentheses whilst keeping tslint rules valid

Actual behavior:

Upon formatting I get:

Expected parentheses around arrow function argument having a body with curly braces

[j-f1]

ban-single-arg-parens

I’m pretty sure that’s what arrowParens: avoid does.

[lydell]

since some folks in our team do not even use it [Prettier]

There we have it. If your whole team isn’t onboard with using Prettier, you’re unfortunately going to have a bad time using Prettier. You’ll always bump into some incompatibility with your team’s style guide (so far you’ve only had trouble with arrow-parens, it seems), and you’ll accidentally commit unnecessarily large diffs by reformatting other parts of the file.

prettier-tslint might help, though.