gradle-docker-plugin: dockerPushImage: Docker credential helpers don't apply

First of all, thank you for the awesome plugin! Couldn’t find your patreon page though…

Expected Behavior

./gradlew dockerPushImage should work on a properly tagged image (docker push <mytag> works fine).

Current Behavior

./gradlew dockerPushImage fails with error

> Could not push image: unauthorized: You don't have the needed permissions to perform this operation, and you may have invalid credentials. To authenticate your request, follow the steps in: https://cloud.google.com/container-registry/docs/advanced-authentication

However, if I do docker push gcr.io/my-project/my-image then it works fine. Because I already followed the steps by that link above and did gcloud auth configure-docker. Looks like it wrote auth tokens to gcr.io to ~/.docker/config.json. So it seems like gradle-docker-plugin just doesn’t use it.

Context

I have the following in my gradle.build.kts:

tasks {
    docker {
        // https://bmuschko.github.io/gradle-docker-plugin/#java-application-plugin
        javaApplication {
            baseImage.set("openjdk:11-jre-slim")
            maintainer.set("")
            ports.set(listOf())
            tag.set("gcr.io/my-project/my-image")
        }
    }
}

And the following in ~/.docker/config.json:

        "credHelpers": {
                "asia.gcr.io": "gcloud",
                "eu.gcr.io": "gcloud",
                "gcr.io": "gcloud",
                "marketplace.gcr.io": "gcloud",
                "staging-k8s.gcr.io": "gcloud",
                "us.gcr.io": "gcloud"
        }

Your Environment

id(“com.bmuschko.docker-java-application”) version “4.4.0” Docker version 18.09.1, build 4c52b90 Google Cloud SDK 231.0.0