feat: add suggestions for redundant wrapping in prefer-regex-literals

[yeonjuan]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[ ] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofix to a rule
[ ] Add a CLI option
[ ] Add something to the core
[x] Other, please explain: Add suggestions to a rule

What changes did you make? (Give an overview)

fixes #16516

Is there anything you'd like reviewers to focus on?

new RegExp(/a/, 'g'); 

// suggestions
/a/g;

In this case, this change will make two suggestions. - #16516 (comment)

new RegExp(/a/i, 'g');

// suggestions
/a/g;
/a/ig;

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[nzakas]

Functionality looks okay to me but would like @mdjermanovic's opinion.

I left some suggestions for ways to clean up the code a bit.

[mdjermanovic]

This example would have a parsing error after the suggestion is applied:

(a)
new RegExp(/b/);

after applying the suggestion, / causes continuation so this is parsed as (a) / b /, and then fails on ;:

(a)
/b/; // Parsing error: Unexpected token ;

We're preventing this in the branch that already had suggestions, so we could do the same for the new suggestions.

eslint/lib/rules/prefer-regex-literals.js

Lines 335 to 337 in ba74253

	const tokenBefore = sourceCode.getTokenBefore(node);
	if (tokenBefore && !validPrecedingTokens.has(tokenBefore.value)) {

[mdjermanovic]

These are quite edge cases, but we should also use canTokensBeAdjacent (like we're using it for the existing suggestions in this rule) for correctness:

// 1.
a/RegExp(/foo/);

// 2.
RegExp(/foo/)in a;

After the suggestions are applied, (1) becomes a line comment //foo/, while in (2) in becomes the flags.

// 1.
a//foo/;

// 2.
/foo/in a;

[yeonjuan]

@nzakas @mdjermanovic Thanks for the reviews. I fixed!

[mdjermanovic]

LGTM, thanks!

Leaving open for @nzakas to check if his reviews have been addressed.

[nzakas]

LGTM. Thanks!

[nzakas]

We just have to wait until we get the "all clear" as far as patch releases go, then this PR is ready for merge.