[Bug]: CO logs StringIndexOutOfBoundsException when tag is not specified for KafkaConnect build

[Frawless]

Bug Description

When a user doesn't specify a tag in DockerOutput part of KafkaConnect build, the image is built and pushed but CO cannot pull it into KafkaConnect pod with the following error:

2023-05-03 20:40:52 DEBUG AbstractOperator:568 - Reconciliation #80(timer) KafkaConnect(infra-namespace/my-cluster-831aae8e): Updated metric strimzi.resource.state[tag(kind=KafkaConnect),tag(name=my-cluster-831aae8e),tag(reason=begin -1, end 42, length 42),tag(resource-namespace=infra-namespace)] = 0
2023-05-03 20:40:52 WARN  AbstractOperator:525 - Reconciliation #80(timer) KafkaConnect(infra-namespace/my-cluster-831aae8e): Failed to reconcile
java.lang.StringIndexOutOfBoundsException: begin -1, end 42, length 42
	at java.lang.String.checkBoundsBeginEnd(String.java:4602) ~[?:?]
	at java.lang.String.substring(String.java:2705) ~[?:?]
	at java.lang.String.substring(String.java:2678) ~[?:?]
	at io.strimzi.operator.cluster.operator.assembly.ConnectBuildOperator.lambda$openShiftBuildWaitForFinish$29(ConnectBuildOperator.java:382) ~[io.strimzi.cluster-operator-0.35.0-SNAPSHOT.jar:0.35.0-SNAPSHOT]
	at io.vertx.core.impl.future.Composition.onSuccess(Composition.java:38) ~[io.vertx.vertx-core-4.3.8.jar:4.3.8]
	at io.vertx.core.impl.future.FutureBase.emitSuccess(FutureBase.java:60) ~[io.vertx.vertx-core-4.3.8.jar:4.3.8]
	at io.vertx.core.impl.future.FutureImpl.tryComplete(FutureImpl.java:211) ~[io.vertx.vertx-core-4.3.8.jar:4.3.8]
	at io.vertx.core.impl.future.Composition$1.onSuccess(Composition.java:62) ~[io.vertx.vertx-core-4.3.8.jar:4.3.8]
	at io.vertx.core.impl.future.FutureBase.emitSuccess(FutureBase.java:60) ~[io.vertx.vertx-core-4.3.8.jar:4.3.8]
	at io.vertx.core.impl.future.FutureImpl.tryComplete(FutureImpl.java:211) ~[io.vertx.vertx-core-4.3.8.jar:4.3.8]
	at io.vertx.core.impl.future.PromiseImpl.tryComplete(PromiseImpl.java:23) ~[io.vertx.vertx-core-4.3.8.jar:4.3.8]
	at io.vertx.core.impl.future.PromiseImpl.onSuccess(PromiseImpl.java:49) ~[io.vertx.vertx-core-4.3.8.jar:4.3.8]
	at io.vertx.core.impl.future.FutureBase.lambda$emitSuccess$0(FutureBase.java:54) ~[io.vertx.vertx-core-4.3.8.jar:4.3.8]
	at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:174) ~[io.netty.netty-common-4.1.87.Final.jar:4.1.87.Final]
	at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:167) ~[io.netty.netty-common-4.1.87.Final.jar:4.1.87.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:470) ~[io.netty.netty-common-4.1.87.Final.jar:4.1.87.Final]
	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:569) ~[io.netty.netty-transport-4.1.87.Final.jar:4.1.87.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[io.netty.netty-common-4.1.87.Final.jar:4.1.87.Final]
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[io.netty.netty-common-4.1.87.Final.jar:4.1.87.Final]
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[io.netty.netty-common-4.1.87.Final.jar:4.1.87.Final]
	at java.lang.Thread.run(Thread.java:833) ~[?:?]

The error should be more user-friendly that will tell to users what is really wrong.

Steps to reproduce

Deploy KafkaConnect with the following configuration

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaConnect 
metadata:
  name: my-connect-cluster
  annotations:
    strimzi.io/use-connector-resources: "true" 
spec:
  ...
  build:
    output:
      type: docker
      image: my-registry.io/my-org/my-connect-cluster # without tag
      pushSecret: my-registry-credentials

Expected behavior

CO will log some user-friendly error messages instead of StringIndexOutOfBoundsException

Strimzi version

main

Kubernetes version

OpenShift 4.13

Installation method

YAML files

Infrastructure

Openstack

Configuration files and logs

No response

Additional context

No response

[scholzj]

Triaged on 4.5.2023: We should add a proper validation that the tag section is present in the image.