bake: fix print output

[crazy-max]

fixes #856

targets groups are not correctly rendered while being printed with bake --print so output cannot be reused.

// docker-bake.hcl
group "default" {
  targets = ["image"]
}

target "image" {
  inherits = ["image"]
  output = ["type=docker"]
}

// docker-bake.json
{
  "group": {
    "default": {
      "targets": [
        "image"
      ]
    }
  },
  "target": {
    "image": {
      "context": ".",
      "dockerfile": "Dockerfile",
      "output": [
        "type=docker"
      ]
    }
  }
}

# docker-compose.yaml
services:
  addon:
    build:
      context: .
      dockerfile: ./Dockerfile
      args:
        CT_ECR: foo
        CT_TAG: bar
    image: ct-addon:bar
    environment:
      - NODE_ENV=test
      - AWS_ACCESS_KEY_ID=dummy
      - AWS_SECRET_ACCESS_KEY=dummy

  aws:
    build:
      dockerfile: ./aws.Dockerfile
      args:
        CT_ECR: foo
        CT_TAG: bar
    image: ct-fake-aws:bar

---

$ docker buildx bake -f docker-compose.yml -f docker-bake.hcl --print
{
  "group": {
    "default": {
      "targets": [
        "image"
      ]
    }
  },
  "target": {
    "image": {
      "context": ".",
      "dockerfile": "Dockerfile",
      "output": [
        "type=docker"
      ]
    }
  }
}

$ docker buildx bake -f docker-bake.json --print
{
  "group": {
    "default": {
      "targets": [
        "image"
      ]
    }
  },
  "target": {
    "image": {
      "context": ".",
      "dockerfile": "Dockerfile",
      "output": [
        "type=docker"
      ]
    }
  }
}

$ docker buildx bake -f docker-compose.yml -f docker-bake.hcl addon --print
{
  "group": {
    "default": {
      "targets": [
        "addon"
      ]
    }
  },
  "target": {
    "addon": {
      "context": ".",
      "dockerfile": "./Dockerfile",
      "args": {
        "CT_ECR": "foo",
        "CT_TAG": "bar"
      },
      "tags": [
        "ct-addon:bar"
      ]
    }
  }
}

$ docker buildx bake -f docker-compose.yml -f docker-bake.hcl addon aws --print
{
  "group": {
    "default": {
      "targets": [
        "addon",
        "aws"
      ]
    }
  },
  "target": {
    "addon": {
      "context": ".",
      "dockerfile": "./Dockerfile",
      "args": {
        "CT_ECR": "foo",
        "CT_TAG": "bar"
      },
      "tags": [
        "ct-addon:bar"
      ]
    },
    "aws": {
      "context": ".",
      "dockerfile": "./aws.Dockerfile",
      "args": {
        "CT_ECR": "foo",
        "CT_TAG": "bar"
      },
      "tags": [
        "ct-fake-aws:bar"
      ]
    }
  }
}

$ docker buildx bake -f docker-compose.yml -f docker-bake.hcl addon aws image --print
{
  "group": {
    "default": {
      "targets": [
        "addon",
        "aws",
        "image"
      ]
    }
  },
  "target": {
    "addon": {
      "context": ".",
      "dockerfile": "./Dockerfile",
      "args": {
        "CT_ECR": "foo",
        "CT_TAG": "bar"
      },
      "tags": [
        "ct-addon:bar"
      ]
    },
    "aws": {
      "context": ".",
      "dockerfile": "./aws.Dockerfile",
      "args": {
        "CT_ECR": "foo",
        "CT_TAG": "bar"
      },
      "tags": [
        "ct-fake-aws:bar"
      ]
    },
    "image": {
      "context": ".",
      "dockerfile": "Dockerfile",
      "output": [
        "type=docker"
      ]
    }
  }
}

cc @eitsupi

Signed-off-by: CrazyMax crazy-max@users.noreply.github.com

[tonistiigi]

PTAL Examples in https://github.com/docker/buildx/blob/master/docs/reference/buildx_bake.md

Can we have a test for this?

[eitsupi]

Don't you also need a test case for a non "default" group name?

[tonistiigi]

What's the reason for changing this signature? Can't you just add the group setting and leave the rest of the function as is.

[crazy-max]

Thought TargetsToBuildOpt had some impact on groups context but it's actually only against targets.

[tonistiigi]

Generally, I don't mind the map return but as this is going to be picked to release branch probably better to keep the change minimal. We can follow up with the type change in another PR that will not be picked later.

[tonistiigi]

This doesn't seem to handle

target "default" {}

case

[tonistiigi]

#15 127.5 bake/bake_test.go:453:2: ineffectual assignment to `m` (ineffassign)
#15 127.5 	m, g, err = ReadTargets(ctx, []File{fTargetImage}, []string{"default"}, nil, nil)
#15 127.5 	^