Add a --fix option for no-tabs

I’m using Node v6.4.0 and ESLint v3.3.1.

I think it would be useful to have an autofix option for the no-tabs rule. The fixer would simply delete any tab characters that it finds, inserting a space if necessary to avoid modifying the AST. (For example, var\tfoo would be replaced with var foo, since replacing it with varfoo would change the semantics of the program)

This would also provide a workaround for https://github.com/eslint/eslint/issues/4274; if all tabs were removed from the file, then the indent autofix could clean up and produce correct output on the next pass.

I would be willing to add this if the issue is accepted.

[platinumazure]

@Alaneor Unfortunately, rules are designed not to be able to know anything about other rules in ESLint, so looking at indent configuration is a non-starter. (Consider that users might not even use indent, so there wouldn’t be a configuration to inspect.) Luckily, for those who do care, multipass auto-fix allows the indent issues to be fixed on a later pass.

[not-an-aardvark]

Thanks for clarifying; that makes more sense now.

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I think we can classify tabs into three different categories:

• Indentation (i.e. tabs on a line before anything else):

Ideally, this would be handled by the indent autofix, since that rule has access to the user’s preferred indentation. In other words, the indent fixer would be able to delete/add indentation tabs as necessary to ensure that a line’s indentation is correct. (This is also discussed in https://github.com/eslint/eslint/issues/4274.)

• Tabs in string/template/regex literals

I think it would be safe for ESLint to replace these tabs with \t. There are other ways to represent a tab character in JS (\x09, \u0009, \011), but I don’t think this replacement would surprise people. (Admittedly, we can’t be 100% certain of which tab representation people would actually want.)

• Tabs as whitespace in other places, e.g. function\tfoo () {}

Tabs in this context aren’t fixed by any other rule. While it would be possible to remove these tabs and replace them with a space, the user might not expect this particular fix. I think this category of tabs is fairly rare (in fact, I’ve never actually seen anyone use tabs like this) so it’s hard to say whether the user would be surprised by a fix to these tabs.

edit: fixed typo \x0009 --> \u0009