Bug: Missing DockerContext doesn't fail validation

[palfrey]

Description:

If you set Dockerfile in a function's metadata, but not DockerContext, sam build seems to just work, except then sam local invoke complains Error: ImageUri not provided for Function: YourFunctionName of PackageType: Image which is very confusing. Note also sam validate doesn't complain abou this.

Steps to reproduce:

Create a correct docker image SAM template, then remove just the DockerContext metadata param.

Observed result:

sam local invoke fails with a confusing error

Expected result:

sam validate fails, or maybe sam build?

Additional environment details (Ex: Windows, Mac, Amazon Linux etc)

1. OS: MacOS
2. sam --version: 1.116.0

{
  "version": "1.116.0",
  "system": {
    "python": "3.11.6",
    "os": "macOS-14.0-arm64-arm-64bit"
  },
  "additional_dependencies": {
    "docker_engine": "23.0.6",
    "aws_cdk": "Not available",
    "terraform": "1.4.1"
  },
  "available_beta_feature_env_vars": [
    "SAM_CLI_BETA_FEATURES",
    "SAM_CLI_BETA_BUILD_PERFORMANCE",
    "SAM_CLI_BETA_TERRAFORM_SUPPORT",
    "SAM_CLI_BETA_RUST_CARGO_LAMBDA"
  ]
}

[fedor-pavlov]

Same for me here! I was caught in this trap yesterday.

[mildaniel]

Thanks @palfrey for reporting. I was able to confirm the behaviour you're describing. The main issue to me here seems not properly handling the missing DockerContext during sam build since it doesn't end up building any images. I will mark it as a bug for the team to prioritize.