[raunak2007]

Fixes #22523

Problem

The kotlinx_serialization and multiplatform templates in kotlin-client/data_class.mustache emitted discriminator.propertyName. DefaultCodegen sets that field through toVarName() (DefaultCodegen.java:3770), so it is a sanitized Kotlin identifier rather than the wire-format name — a discriminator declared as $type was emitted as dollarType.

This left the generated client internally inconsistent. oneof_class.mustache already writes and reads the discriminator using propertyBaseName (lines 142, 154), and typeInfoAnnotation.mustache uses propertyBaseName in kotlin-client, kotlin-server, and kotlin-spring. These two annotation lines were the only remaining uses of propertyName.

Fix

Switch both lines to propertyBaseName, wrapped in lambda.escapeDollar — the same lambda already used ~40 times in this file for baseName — because the raw name lands inside a Kotlin string literal, where an unescaped $ begins an interpolation.

Verification

Same spec, same command, only the template differs:

template	generated
before	discriminator = "dollarType"
propertyBaseName alone	discriminator = "$type" — correct name, does not compile
propertyBaseName + escapeDollar	discriminator = "\$type" — correct and compiles

./gradlew compileKotlin passes on the generated kotlin-allOf-special-discriminator-kotlinx-serialization sample.

Regenerating all bin/configs/kotlin-*.yaml produces no diff in existing samples — every current spec uses a discriminator that is already a valid identifier, so toVarName() was a no-op there.

New samples

Adds polymorphism-special-discriminator.yaml (a copy of the existing polymorphism.yaml with a $type discriminator) plus two configs covering both affected templates, giving CI a regression case.

Relation to #23633

That draft addresses Kotlin escaping broadly but is currently blocked on build failures. This is a narrow, independent fix for the discriminator case only.

cc @karismann @Zomzog @andrewemery @4brunu @yutaka0m @stefankoppier @e5l @dennisameling

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Summary by cubic

Fixes Kotlin client generation for polymorphic discriminators when using kotlinx-serialization and the multiplatform library. Previously, @JsonClassDiscriminator used a transformed name (e.g., $type -> dollarType), which disagreed with oneof_class.mustache and broke serialization; now it uses the raw discriminator name with escaped dollars. Fixes #22523.

• Update modules/openapi-generator/src/main/resources/kotlin-client/data_class.mustache to use discriminator.propertyBaseName wrapped with lambda.escapeDollar in both kotlinx_serialization and multiplatform paths.
• Add a test spec with a $type discriminator and generate samples for kotlinx-serialization and multiplatform to validate the fix.

^{Written for commit 54a99bb. Summary will update on new commits.}

[cubic-dev-ai]

All reported issues were addressed across 77 files

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[raunak2007]

Re: the cubic review — a note on scope.

Six of the seven findings are in generated sample output (ApiClient.kt, ApiKeyAuth.kt, BirdApi.md), byte-identical to what every existing Kotlin sample contains. They appear here only because the new sample directories make that code show up as new files.

The markdown table issue was real but predated this PR — root cause was api_doc.mustache emitting the header inside {{#-last}}. Fixed separately in #24742.

The remaining finding (escapeDollar on data_class.mustache) is addressed in the thread above.

Resolving these to keep the diff readable.

[wing328]

tested the new samples locally and the tests passed

will add these to the CI after merging this PR