KTOR-8602 Fix handling of optional module parameters

[osipxd]

Subsystem
Server

Motivation
KTOR-8602 Module parameter type Application.() -> kotlin.Unit is not supported in 3.2.0
KTOR-8608 Ktor fails to boot with default jvminline argument

Solution

• Fix order of parameter checks. Move checks throwing an exception to the end.
• Check name of Kotlin function instead of Java function to handle mangled names properly

[coderabbitai]

Walkthrough

The changes update parameter resolution logic in the server engine to prioritize dependency injection before throwing exceptions for "Application"-typed parameters. In tests, module tracking is refactored from a single attribute to a set of loaded module names, with new extension functions and assertions reflecting this approach.

Changes

File(s)	Change Summary
.../engine/internal/CallableUtils.kt	Adjusted parameter resolution to attempt injection before throwing exceptions for "Application"-typed parameters; minor formatting.
.../tests/hosts/EmbeddedServerReloadingTests.kt	Refined imports; replaced single module attribute with a mutable set of loaded module names; added extension property and function; replaced one top-level function with three new ones including an inline value class; updated test assertions accordingly.

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📥 Commits

Reviewing files that changed from the base of the PR and between e68b729 and 5b7e709.

📒 Files selected for processing (2)

• ktor-server/ktor-server-core/jvm/src/io/ktor/server/engine/internal/CallableUtils.kt (2 hunks)
• ktor-server/ktor-server-core/jvm/test/io/ktor/tests/hosts/EmbeddedServerReloadingTests.kt (6 hunks)

🚧 Files skipped from review as they are similar to previous changes (2)

• ktor-server/ktor-server-core/jvm/src/io/ktor/server/engine/internal/CallableUtils.kt
• ktor-server/ktor-server-core/jvm/test/io/ktor/tests/hosts/EmbeddedServerReloadingTests.kt

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

ktor-server/ktor-server-core/jvm/test/io/ktor/tests/hosts/EmbeddedServerReloadingTests.kt (1)

9-28: Review import additions for necessity and compliance.

The new imports generally look appropriate for the added functionality. However, line 18 imports addLoadedModule from the same class's companion object, which may be unnecessary since it's accessible within the same class scope.

Consider removing the self-import:

-import io.ktor.tests.hosts.EmbeddedServerReloadingTests.Companion.addLoadedModule

📜 Review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between a6d91b8 and e68b729.

📒 Files selected for processing (2)

• ktor-server/ktor-server-core/jvm/src/io/ktor/server/engine/internal/CallableUtils.kt (2 hunks)
• ktor-server/ktor-server-core/jvm/test/io/ktor/tests/hosts/EmbeddedServerReloadingTests.kt (6 hunks)

🚧 Files skipped from review as they are similar to previous changes (1)

• ktor-server/ktor-server-core/jvm/src/io/ktor/server/engine/internal/CallableUtils.kt

🧰 Additional context used

📓 Path-based instructions (2)

`**/*.kt`: Include copyright header in new files. Use star imports for io.ktor.* packages (configured in .editorconfig). Max line length: 120 characters. Indent with 4 spaces.

**/*.kt: Include copyright header in new files.
Use star imports for io.ktor.* packages (configured in .editorconfig).
Max line length: 120 characters.
Indent with 4 spaces.

• ktor-server/ktor-server-core/jvm/test/io/ktor/tests/hosts/EmbeddedServerReloadingTests.kt

`**/test/**`: Tests are organized by platform in module's test directories.

**/test/**: Tests are organized by platform in module's test directories.

• ktor-server/ktor-server-core/jvm/test/io/ktor/tests/hosts/EmbeddedServerReloadingTests.kt

🔇 Additional comments (3)

ktor-server/ktor-server-core/jvm/test/io/ktor/tests/hosts/EmbeddedServerReloadingTests.kt (3)

399-402: Excellent test coverage for different default parameter types.

The test now properly validates the handling of multiple module functions with different types of default parameters (Boolean, function type, and inline value class), which directly addresses the PR objectives for KTOR-8602 and KTOR-8608.

Also applies to: 415-422

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529-536: Well-designed module tracking infrastructure.

The new module tracking approach using a set is more flexible than the previous single-attribute method and properly supports testing multiple module functions. The use of computeIfAbsent ensures thread-safe initialization of the mutable set.

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677-690: Comprehensive testing of problematic default parameter types.

These module functions excellently test the specific issues mentioned in the PR objectives:

• defaultArgBoolean: Standard Boolean default parameter
• defaultArgContainingApplicationWord: Function type with Application receiver (KTOR-8602)
• defaultArgInline: Inline value class default parameter (KTOR-8608)

The InstanceId inline value class is properly defined and demonstrates the inline default argument handling fix.