fix(eslint-plugin): [no-namespace] fix false positive for exported namespaces when allowDeclarations=true

[zachkirsch]

PR Checklist

• Addresses an existing open issue: fixes [no-namespace] Adding 'export' yields false positive when allowDeclarations=true #4843
• That issue was marked as accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

Before this PR, this doesn't produce any warnings if allowDeclarations is true:

declare namespace foo {
    namespace bar {
        namespace baz {}
    }
}

This DOES produce a warning if allowDeclarations is true

declare namespace foo {
    export namespace bar {
        namespace baz {}
    }
}

After this PR, the second example also doesn't produce a warning.

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• Node 12.x - nx test @typescript-eslint/eslint-plugin-internal
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• Node 12.x - nx test @typescript-eslint/parser
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• Node 12.x - nx test @typescript-eslint/eslint-plugin-tslint
• Node 12.x - nx test @typescript-eslint/eslint-plugin
• Node 12.x - nx run-many --target=build --all --parallel --exclude website --exclude website
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• Node 12.x - nx test @typescript-eslint/visitor-keys
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• Node 12.x - nx run-many --target=build --all --parallel --exclude website --exclude website
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• Node 12.x - nx run-many --target=build --all --parallel --exclude website --exclude website

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[typescript-eslint]

Thanks for the PR, @zachkirsch!

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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[codecov]

Codecov Report

Merging #4844 (58c1391) into main (88ed9ec) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 58c1391 differs from pull request most recent head 9b8961e. Consider uploading reports for the commit 9b8961e to get more accurate results

@@           Coverage Diff           @@
##             main    #4844   +/-   ##
=======================================
  Coverage   94.23%   94.24%           
=======================================
  Files         152      152           
  Lines        8281     8282    +1     
  Branches     2694     2695    +1     
=======================================
+ Hits         7804     7805    +1     
  Misses        263      263           
  Partials      214      214           

Flag	Coverage Δ
unittest	94.24% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/eslint-plugin/src/rules/no-namespace.ts	100.00% <100.00%> (ø)

[JoshuaKGoldberg]

I think what @armano2 meant was that more deeply nested namespaces need a bit more checking. Once you add a few more edge case tests I think you'll see.

Otherwise looks great so far!

[JoshuaKGoldberg]

I think there are few more edge cases that should be tested around declared namespaces inside a non-declared one, both exported and not:

namespace Outer {
  declare namespace Declared {
    /* export */ namespace InsideDeclared {
       // and maybe more namespaces in here
    }
  }
}

[zachkirsch]

@JoshuaKGoldberg thanks for the reply! I added a bunch more tests to check all the cases.

more deeply nested namespaces need a bit more checking.

I think these are handled by the recursive call at the end of isDeclaration()

[JoshuaKGoldberg]

Wonderful, thanks! 👍