feat(eslint-plugin): [no-unnec-cond] check optional chaining

[jridgewell]

This adds type checking around the the new optional-chaining feature. With this, it becomes invalid to start an optional chain when the base value is known to be not-nullish.

// Good
declare const foo: string | null;
declare const bar: null | (() => {});
foo?.length;
foo?.slice();
bar?.();

// Bad
declare const baz: string;
declare const qux: (() => {});
baz?.length;
baz?.slice();
baz.slice?.();
qux?.();

[typescript-eslint]

Thanks for the PR, @jridgewell!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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[bradzacher]

Thanks for the PR.
I think that this functionality would be better suited within the no-unnecessary-condition rule.
Would you please be able to move it in there?

[jridgewell]

Done.

[jridgewell]

Updated the docs to get the tests to pass.

[codecov]

Codecov Report

Merging #1315 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1315      +/-   ##
==========================================
+ Coverage   93.92%   93.94%   +0.01%     
==========================================
  Files         131      131              
  Lines        5847     5860      +13     
  Branches     1657     1661       +4     
==========================================
+ Hits         5492     5505      +13     
  Misses        188      188              
  Partials      167      167

Impacted Files	Coverage Δ
...slint-plugin/src/rules/no-unnecessary-condition.ts	100% <100%> (ø)	⬆️

[bradzacher]

LGTM - thanks for this

Nice work using nullThrows, I hadn't documented it yet.

[StephanBijzitter]

Please note: the release notes use the pull request title, so I updated my config to include no-unnec-cond and it didn't very much like it. Was a bit confusing :-)

[bradzacher]

Sorry, ESLint semi enforces commit message length when doing squash merges. It's also nice to keep things short enough (72 characters) so that the commit history on github doesn't truncate the message.

It's one of the pains of using semantic commit messages; it takes a lot of the character budget to do feat(eslint-plugin):

[StephanBijzitter]

No worries, we have the same issue ourselves :-)

The way we solve it is when squash-merging a pull request, we edit the body of the commit message to make it match again