First line on Dockerfile's Syntax seems to terminate debugging session instantly

[danielschulz]

Thank you for this cool OpenSource project!

I have an issue, when debugging my Dockerfiles, which start using Docker BuildKit's Dockerfile-Syntax declarations like this one.

When I remove this first line "# syntax = docker/dockerfile:1.4.3", the debugger IS working perfectly. Having this first line included results in weird output of it:

The debugger seems to not understand this line and terminates directly — even when this image is present locally in my repository.

[ktock]

@danielschulz Thank you for reporting this issue. Which version of buildg are you using?

And according to the 1st screenshot you shared, BASE_IMAGE arg at line 5 seems blank.

# syntax=docker/dockerfile:1.4.3
...(omit)...
ARG BASE_IMAGE
FROM ${BASE_IMAGE}

Could you set BASE_IMAGE arg to an existing image and try it again?

If the above doesn't solve the issue, could you try $ buildg debug /path/to/your/dockerfile/dir on terminal and share the output?

[danielschulz]

Thank you for getting back to me so swiftly. This got nothing to do with the empty build argument: I provided this in both cases. So the only difference in working and not-working setups was the first line pertaining Dockerfile's Syntax.

I am using the latest buildg, which I build from sources using GoLang 17.5. I used this Docker image to build it and am using buildg wo/ any container since this...
golang:1.17.5-buster
(Building image)

I am using Docker version:

Do you need more information to work on my findings?

[ktock]

@danielschulz I've tried to reproduce your problem following the steps you provided but can't reproduce the problem and all builds worked perfectly on my matchine.

1. Could you try the following test on your environment and provide the result?
2. If the following tests work perfectly on your machine as well, could you provide a minimal complete reproducer for the issue you're reporting so that we can analyze this problem deeper?

Tests on my machine:

• Version information:
  • Ubuntu 20.04
  • buildg: 176d749 (main)
  • docker

    $ docker version
    Client: Docker Engine - Community
     Version:           20.10.21
     API version:       1.41
     Go version:        go1.18.7
     Git commit:        baeda1f
     Built:             Tue Oct 25 18:02:21 2022
     OS/Arch:           linux/amd64
     Context:           default
     Experimental:      true
    
    Server: Docker Engine - Community
     Engine:
      Version:          20.10.21
      API version:      1.41 (minimum version 1.12)
      Go version:       go1.18.7
      Git commit:       3056208
      Built:            Tue Oct 25 18:00:04 2022
      OS/Arch:          linux/amd64
      Experimental:     false
     containerd:
      Version:          1.6.9
      GitCommit:        1c90a442489720eec95342e1789ee8a5e1b9536f
     runc:
      Version:          1.1.4
      GitCommit:        v1.1.4-0-g5fd4c4d
     docker-init:
      Version:          0.19.0
      GitCommit:        de40ad0
    

  • vscode: v1.7.3
  • vscode-buildg: v0.2.0

Preparation: build and install the latest commit of buildg

$ pwd
/home/ktock/go/src/github.com/ktock/buildg
$ cat <<'EOF' > Dockerfile.repro
FROM golang:1.17.5-buster AS dev
COPY . /go/src/github.com/ktock/buildg
WORKDIR /go/src/github.com/ktock/buildg
RUN PREFIX=/out/ make

FROM scratch
COPY --from=dev /out/buildg /
EOF
$ docker build --output=type=local,dest=/tmp/out/ -f Dockerfile.repro .
$ mv /tmp/out/buildg /home/ktock/.local/bin/buildg
$ buildg version
buildg v999.999.999-25-g176d749 176d749a80081d6a5ca47e1d5f39b5d30dffc2c9

Create Dockerfile to test

Contains # syntax=.

$ mkdir -p /tmp/test && cat <<'EOF' >  /tmp/test/Dockerfile
# syntax=docker/dockerfile:1.4.3
FROM ubuntu:22.04
RUN echo 1 > /1
RUN echo 2 > /2
RUN echo 3 > /3
RUN echo 4 > /4
EOF

Test on CLI with # syntax=

Everything works perfectly.

$ buildg debug /tmp/test/
...(omit)...
INFO[2022-11-15T17:36:50+09:00] debug session started. type "help" for command reference. 
Filename: "Dockerfile"
      1| # syntax=docker/dockerfile:1.4.3
 =>   2| FROM ubuntu:22.04
      3| RUN echo 1 > /1
      4| RUN echo 2 > /2
      5| RUN echo 3 > /3
(buildg) n
...(omit)...
#9 [2/5] RUN echo 1 > /1
Filename: "Dockerfile"
      1| # syntax=docker/dockerfile:1.4.3
      2| FROM ubuntu:22.04
 =>   3| RUN echo 1 > /1
      4| RUN echo 2 > /2
      5| RUN echo 3 > /3
      6| RUN echo 4 > /4
(buildg) exec cat /1
1

Test on VS Code with # syntax=

Everything works perfectly.

$ mkdir -p /tmp/test/.vscode && cat <<'EOF' > /tmp/test/.vscode/launch.json 
{
	"version": "0.2.0",
	"configurations": [
		{
			"type": "dockerfile",
			"request": "launch",
			"name": "Debug Dockerfile",
			"program": "${workspaceFolder}/Dockerfile",
			"stopOnEntry": true,
		},
	]
}
EOF

[danielschulz]

Thank you so much for your setup. I will give this a try soon.

For the time being: I am working on your latest release and experience this issue. Here are my versions, which tend to align with your mentioned ones.

Versions

Here is my failing attempt in these versions shown before.

buildg-issue-Dockerfile-syntax2.webm