[naming-convention] Allow multiple underscore

[jhnns]

Repro

Hey ho 👋, this is a feature request. What do you think of allowing multiple leading or trailing underscores? There are some libraries that use double underscore (__) to avoid name clashes. Probably the most popular one is GraphQL where you can specify a __typename (see here).

Personally, I want to use camelCase or PascalCase and I'm ok with people pre- or postfixing names with underscores. We could introduce a 4th value for the leadingUnderscore and trailingUnderscore option that is called allowMultiple, like this:

{
  "rules": {
    "@typescript-eslint/naming-convention": ["warn", {
        "format": ["camelCase", "PascalCase", "UPPER_CASE"],
        "leadingUnderscore": "allowMultiple",
        "selector": "default",
        "trailingUnderscore": "allowMultiple"
    }]
  }
}

[bradzacher]

It's a pattern people use for protected members as well.
Happy to accept a PR to add the option!

[felixfbecker]

Also React's dangerouslySetInnerHTML={{ __html: "" }}

[ScottAwesome]

I want to comment here as well, as I would love to see this. I tried doing a custom regex filter, so if anything started with double leading underscores, it wouldn't error:

const propertySetting = {
                selector: 'property',
                format: ['camelCase', 'PascalCase', 'UPPER_CASE'],
                filter: {
                    regex: '^(__|_)([0-9A-Za-z]+)$',
                    match: false,
                },
            };

No such luck, giving me errors.

If anyone has a secret sauce here that does work, please share!

Also, another option to think about is allowing optionalPrefixes instead? if I do prefix with a blank string, eslint throws.

[joh-klein]

@ScottAwesome I got your filter to work, when the ONLY rule was the one you posted (propertySetting). When there are other rules that fit (in my case I had another one with selector: 'default'), it will apply those rules again – and possibly fail.

[BorisZubchenko]

For those looking for a __typename solution:

{
    "selector": "property",
    "filter": "__typename",
    "format": null
 }

Good:

console.log({
  __typename: 'Type'
});

[ScottAwesome]

For those looking for a __typename solution:

{
    "selector": "property",
    "filter": "__typename",
    "format": null
 }

Good:

console.log({
  __typename: 'Type'
});

This doesn’t solve for the fact I only want certain formats otherwise though, does it? See my previous example where it won’t work if other rules are being applied

[ab-pm]

What I found to be working is a prefix:

{
	selector: 'property',
	prefix: ['__'],
	format: ['camelCase']
},

However, for some reason (not sure if it's a bug) I had to restrict the normal property rule to not match the underscored properties, as it would complain otherwise:

{
	selector: 'property',
	filter: '^(?!__)',
	format: […]
},