[Enhancement]: Override toString() for ChainedImageNameSubstitutor to return type of "wrapped" ImageNameSubstitutor

[jxblum]

Module

Core

Proposal

If users configure a custom ImageNameSubstitutor (for example), then this instance will get wrapped by Testcontainers when the configuration is evaluated.

If an error occurs, regardless of context (in my case, I am using Spring) then the "configured" ImageNameSubstitutor in the RemoteDockerImage instance created from an DockerImageName by the container, is quite "cryptic":

2023-05-13 02:44:13,155 ERROR g.springframework.boot.SpringApplication: 822 - Application run failed
org.springframework.beans.factory.BeanCreationException: 
Error creating bean with name 'CassandraContainer' defined in example.app.crm.config.TestcontainersCassandraConfiguration: 
Failed to instantiate [org.testcontainers.containers.GenericContainer]: Factory method 'cassandraContainer' threw exception with message: 
Can't get Docker image: RemoteDockerImage(
  imageName=cassandra:3.11.15, 
  imagePullPolicy=DefaultPullPolicy(), 
  imageNameSubstitutor=org.testcontainers.utility.ImageNameSubstitutor$ChainedImageNameSubstitutor@4904144d
)

It is not apparent from this ERROR log output whether the custom ImageNameSubstitutor was actually in use here, and users have to make an effort (logging, debugging, etc) to determine if the custom ImageNameSubstitutor was actually applied or not.

In my case, I had to add logging to my "custom" ImageNameSubstitutor to determine whether it was actually being applied and used by Testcontainers during Docker Image Name resolution since my library was being built remotely in a Jenkins CI environment where debugging is nearly impossible.

This:

imageNameSubstitutor=org.testcontainers.utility.ImageNameSubstitutor$ChainedImageNameSubstitutor@4904144d

... is quite useless.

The toString() method of the static inner ChainedImageNameSubstitutor class (source) could be overridden to return getDescription() (source).

Altneratively, the ImageNameSubstitutor abstract class could override the toString() method to return getDescription(), like so:

abstract class ImageNameSubstitutor {

  @Override
  public String toString() {
    return getDescription();
  }
}

In this way, all extensions of ImageNameSubstitutor would benefit and also be consistent without any extra effort on behalf of your users.

[eddumelendez]

Hi @jxblum, Testcontainers for Java 1.19.1 was just released and contains this change. Thanks for the report.

[jxblum]

Hi @eddumelendez - Thank you so much.