Feature request: Docker build logs on failure

[palfrey]

Describe your idea/feature/enhancement

When you run sam build --use-container and your Docker build fails, you get something like the following

Building image for EmploymentTimeEmployeeCachingFunction function
Setting DockerBuildArgs for EmploymentTimeEmployeeCachingFunction function
Failed building function EmploymentTimeEmployeeCachingFunction

Build Failed
Error: The command '/bin/sh -c exit 1' returned a non-zero code: 1

This isn't very useful, as I've got no idea what the build logs actually look like that caused this.

Proposal

Dump the docker build logs on failure. So, for the above example, instead I would like something like

Building image for EmploymentTimeEmployeeCachingFunction function
Setting DockerBuildArgs for EmploymentTimeEmployeeCachingFunction function
Failed building function EmploymentTimeEmployeeCachingFunction
Step 1/19 : FROM public.ecr.aws/lambda/python:3.11 AS base
 ---> 37318d609dfb
Step 2/19 : RUN exit 1
 ---> [Warning] The requested image's platform (linux/amd64) does not match the detected host platform (linux/arm64/v8) and no specific platform was requested
 ---> Running in 6420d9378807
The command '/bin/sh -c exit 1' returned a non-zero code: 1
Build Failed
Error: The command '/bin/sh -c exit 1' returned a non-zero code: 1

Additional Details

The demo log was generated with the following extra code in the BuildError handler in app_builder.py

            for log in ex.build_log:
                if "stream" in log:
                    self._stream_writer.write_str(log["stream"])
                elif "error" in log:
                    self._stream_writer.write_str(log["error"])

[mndeveci]

Thanks for creating this issue.

This makes sense from our side, and it should improve the user experience in general. Since you already find the point which needs the update, would like to raise a pull request with the change?

[palfrey]

See #7675