[BUG][typescript-fetch] Fixed TypeScript code generation for oneOf using arrays

[psegalen]

This PR just fixes the syntax of the generated code, no opinionated new code, no change of any nature to anything, just some syntax fix.
It fixes issue #22779

Fix is only about balancing unbalanced parentheses and using the correct variables, nothing else.

Again, as this doesn't change anything about anything already functional and being in a kind of a hurry, I haven't walked through the PR checklist, sorry.

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Summary by cubic

Fixed TypeScript code generation for oneOf arrays so Date and DateTime arrays parse and serialize correctly. This corrects variable usage and missing parentheses in the template.

• Bug Fixes
  • Use item (not json) in json.every and map.
  • Balance missing parentheses in if conditions and map calls.
  • Map to new Date(value) when parsing arrays; serialize Date arrays with toISOString().substring(0,10) and DateTime arrays with item.toISOString().

^{Written for commit 785ecb4. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

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[wing328]

i add some tests via #22870 and incorporate your changes in this PR but there's no change in samples (TypeScript Fetch output) and the CI tests still failed.

can you please take a look when you've time?

[wing328]

cc @TiFu (2017/07) @taxpon (2017/07) @sebastianhaas (2017/07) @kenisteward (2017/07) @Vrolijkx (2017/09) @macjohnny (2018/01) @topce (2018/10) @akehir (2019/07) @petejohansonxo (2019/11) @amakhrov (2020/02) @davidgamero (2022/03) @mkusaka (2022/04) @joscha (2024/10) for review as well

[macjohnny]

thanks for the fix!

[wing328]

@psegalen given that it's now merged. can you please test the latest master to see if it's working for your use cases?

[wing328]

@psegalen you can test with the snapshot version published to central maven repo e.g. https://central.sonatype.com/repository/maven-snapshots/org/openapitools/openapi-generator-cli/7.20.0-SNAPSHOT/openapi-generator-cli-7.20.0-20260204.115301-105.jar

we will cut a release next week. just want to make sure the your fix works for your use cases as expected

otherwise, we can consider reverting the change.