TempDir in trait not initialized

[thecodesmith]

Describe the bug

The @TempDir annotation does not work when defined in a trait.

To Reproduce

Adding the following trait and test class in TempDirExtensionSpec reproduces the problem:

trait TempDirTrait {
  @TempDir Path tmp
  @TempDir @Shared Path sharedTmp
}

class TempDirTraitSpec extends Specification implements TempDirTrait {
  void "TempDir works for inherited fields"() {
    expect:
    tmp != null
  }

  void "TempDir works for inherited shared fields"() {
    expect:
    sharedTmp != null
  }
}

Expected behavior

The temporary directory is initialized and the above tests pass.

Actual behavior

Condition not satisfied:

tmp != null
|   |
|   false
null

Condition not satisfied:

tmp != null
|   |
|   false
null

Java version

openjdk version "11.0.13" 2021-10-19 LTS
OpenJDK Runtime Environment Corretto-11.0.13.8.1 (build 11.0.13+8-LTS)
OpenJDK 64-Bit Server VM Corretto-11.0.13.8.1 (build 11.0.13+8-LTS, mixed mode)

Buildtool version

------------------------------------------------------------
Gradle 7.3.3
------------------------------------------------------------

Build time:   2021-12-22 12:37:54 UTC
Revision:     6f556c80f945dc54b50e0be633da6c62dbe8dc71

Kotlin:       1.5.31
Groovy:       3.0.9
Ant:          Apache Ant(TM) version 1.10.11 compiled on July 10 2021
JVM:          11.0.13 (Amazon.com Inc. 11.0.13+8-LTS)
OS:           Mac OS X 12.1 x86_64

What operating system are you using

Mac

Dependencies

N/A - test created in Spock codebase

Additional context

This approach using a trait with a temporary directory previously worked in Spock 1.x using a JUnit @Rule TemporaryFolder. I am updating my test utils library for Spock 2 and I'd like to use the same approach if possible.

This issue is similar to the one here (#1229) for using @TempDir in a base class, which was solved.

[leonard84]

Unfortunately field extensions don't work in traits, as Groovy doesn't support traits with AST some necessary metadata isn't generated for fields contributed by traits.

[thecodesmith]

Ah, that is unfortunate. Thanks for the explanation. I will find another way to implement it then.