docker-cache-copy-path-mismatch

Detects Dockerfiles that COPY a Gradle or Maven build configuration file that does not exist in the repository, when an alternative with a different extension does exist.

Why it matters

Dockerfiles often use an early COPY instruction to prime dependency caches before the full source copy:

COPY build.gradle.kts .
RUN gradle build -x bootJar

If build.gradle.kts does not exist but build.gradle does, the cache layer is broken — it copies a non-existent file (or fails silently depending on buildkit settings) and the dependency cache is never primed.

This is common after a Gradle Groovy-to-Kotlin migration where the Dockerfile was not updated.

Detection

Reports when:

• A Dockerfile COPY instruction references a Gradle or Maven configuration file
• That file does not exist at the expected path in the build context
• An alternative file with the correct extension does exist in the same directory

Supported file pairs

Exclusions

Does not report when:

• The COPY source contains shell variables or build args ($, {)
• The COPY uses --from= (multi-stage build reference)
• The file actually exists in the build context
• No alternative extension file exists in the build context

Severity

warning — the cache layer almost certainly does not work as intended.