Lint for invisible Unicode characters other than ZWSP

[bugadani]

This PR extends the existing zero_width_space lint to look for other invisible characters as well (in this case, \\u{ad} soft hyphen.

I feel like this lint is the logical place to add the check, but I also realize the lint name is not particularly flexible, but I also understand that it shouldn't be renamed for compatibility reasons.

Open questions:

• What other characters should trigger the lint?
• What should be done with the lint name?
• How to indicate the change in functionality?

Motivation behind this PR: rust-lang/rust#77417 - I managed to shoot myself in the foot by an invisible character pasted into my test case.

changelog: rename [zero_width_space] to [invisible_characters] and add SHY and WJ to the list.

[rust-highfive]

r? @ebroto

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[ebroto]

About the open questions:

What other characters should trigger the lint?

I'm really not an expert in this field. Taking a look at this Wikipedia entry, there are some other invisible characters (second table) which could be candidates.
My main concern would be including characters that could be legitimately used in languages I'm not familiar with, so I would prefer to be conservative here. Maybe the WORD JOINER one could be a candidate? If we are not sure I would prefer not to include others.

What should be done with the lint name?

There's a mechanism for renaming lints. You can find an example in #3554. It's a bit old PR, but self-contained, except for the test about renaming lints, you can omit that.

How to indicate the change in functionality?

A new name for the lint should suffice. What about invisible_characters that you used when linting?

[bugadani]

I'm really not an expert in this field. Taking a look at this Wikipedia entry, there are some other invisible characters (second table) which could be candidates.

Oh, I intended this question to a broader audience, not placing the burden of figuring out on you. Just in case somebody would have a stronger opinion here.

My main concern would be including characters that could be legitimately used in languages I'm not familiar with, so I would prefer to be conservative here. Maybe the WORD JOINER one could be a candidate? If we are not sure I would prefer not to include others.

I've added WJ, that seems obvious enough. I don't think language support is an issue here - if a character is invisible, I think people should prefer writing out the escape code instead in any language. But I may have wrong assumptions and preferences here.

There's a mechanism for renaming lints. You can find an example in #3554. It's a bit old PR, but self-contained, except for the test about renaming lints, you can omit that.

Thanks, I've renamed the lint to invisible_characters.

[ebroto]

LGTM, let's wait for CI and we can merge it.

Oh, I intended this question to a broader audience, not placing the burden of figuring out on you

Of course! Sorry if that sounded harsh, it was not the intention.

I don't think language support is an issue here - if a character is invisible, I think people should prefer writing out the escape code instead in any language

That makes sense, but I would prefer to be cautious. I think adding those two is a good improvement in any case.

[ebroto]

@bors r+

Thanks!

[bors]

📌 Commit 572e4c4 has been approved by ebroto

[bors]

⌛ Testing commit 572e4c4 with merge 15a7950...

[bugadani]

Of course! Sorry if that sounded harsh, it was not the intention.

Not at all, no worries. :) Thanks for the review!

[bors]

💔 Test failed - checks-action_test

[ebroto]

@bors retry (missing changelog)

[bors]

⌛ Testing commit 572e4c4 with merge 9408c68...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: ebroto
Pushing 9408c68 to master...