Error when ENTRYPOINT is set to empty array

[sbienkow-ninja]

Expected behavior

When I set ENTRYPOINT to empty array, skaffold parses it correctly and the image is built without entrypoint (removing entrypoint from parent image).

FROM someimage
ENTRYPOINT []

Actual behavior

When checking cache, the following error is thrown:

getting hash for artifact "<IMAGE>": getting dependencies for "<IMAGE>": parsing dockerfile "<PATH>/Dockerfile": dockerfile parse error line 12: ENTRYPOINT requires at least one argument

Information

• Skaffold version: v1.33.0
• Operating system: Arch
• Installed via: yay (AUR package skaffold-bin)
• Contents of skaffold.yaml:

apiVersion: skaffold/v2beta23
kind: Config
build:
  local:
    useBuildkit: true
    push: false
  artifacts:
    - image: example
      context: ./example/

Steps to reproduce the behavior

1. Create following setup:

# 11:33:58 sbienkow@sebixE595 /tmp/skaffold $ :)
tree
.
├── example
│   └── Dockerfile
└── skaffold.yaml

1 directory, 2 files
# 11:34:11 sbienkow@sebixE595 /tmp/skaffold $ :)
cat skaffold.yaml
apiVersion: skaffold/v2beta23
kind: Config
build:
  local:
    useBuildkit: true
    push: false
  artifacts:
    - image: example
      context: ./example/
# 11:34:13 sbienkow@sebixE595 /tmp/skaffold $ :)
cat example/Dockerfile
FROM ubuntu
ENTRYPOINT []

2. Run skaffold build

$ skaffold build -vdebug
DEBU[0000] skaffold API not starting as it's not requested  subtask=-1 task=DevLoop
INFO[0000] Skaffold &{Version:v1.33.0 ConfigVersion:skaffold/v2beta24 GitVersion: GitCommit:251c0406b3f9ef149cfa084d912874fd080e1e97 BuildDate:2021-10-07T19:30:49Z GoVersion:go1.14.14 Compiler:gc Platform:linux/amd64 User:}  subtask=-1 task=DevLoop
INFO[0000] Loaded Skaffold defaults from "/home/sbienkow/.skaffold/config"  subtask=-1 task=DevLoop
DEBU[0000] config version out of date: upgrading to latest "skaffold/v2beta24"  subtask=-1 task=DevLoop
DEBU[0000] parsed 1 configs from configuration file /tmp/skaffold/skaffold.yaml  subtask=-1 task=DevLoop
DEBU[0000] Defaulting deploy type to kubectl             subtask=-1 task=DevLoop
INFO[0000] Using kubectl context: kind-kind              subtask=-1 task=DevLoop
DEBU[0000] Running command: [minikube version --output=json]  subtask=-1 task=DevLoop
DEBU[0000] Command output: [{"commit":"0a0ad764652082477c00d51d2475284b5d39ceed-dirty","minikubeVersion":"v1.23.2"}
]  subtask=-1 task=DevLoop
DEBU[0000] Running command: [/usr/bin/minikube profile list -o json --user=skaffold]  subtask=-1 task=DevLoop
DEBU[0000] setting Docker user agent to skaffold-v1.33.0  subtask=-1 task=DevLoop
DEBU[0000] Using builder: local                          subtask=-1 task=DevLoop
INFO[0000] build concurrency first set to 1 parsed from *local.Builder[0]  subtask=-1 task=DevLoop
INFO[0000] final build concurrency value is 1            subtask=-1 task=DevLoop
Generating tags...
 - example -> DEBU[0000] Running command: [git describe --tags --always]  subtask=-1 task=Build
DEBU[0000] generating tag: unable to find git commit: running [git describe --tags --always]
 - stdout: ""
 - stderr: "fatal: not a git repository (or any parent up to mount point /)\nStopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).\n"
 - cause: exit status 128  subtask=example task=Build
DEBU[0000] Using a fall-back tagger                      subtask=example task=Build
example:latest
Some taggers failed. Rerun with -vdebug for errors.
INFO[0000] Tags generated in 1.826506ms                  subtask=-1 task=Build
Checking cache...
 - example: Error checking cache.
DEBU[0000] Running command: [tput colors]                subtask=-1 task=DevLoop
DEBU[0000] Command output: [256
]                        subtask=-1 task=DevLoop
getting hash for artifact "example": getting dependencies for "example": parsing dockerfile "/tmp/skaffold/example/Dockerfile": dockerfile parse error line 2: ENTRYPOINT requires at least one argument
DEBU[0000] exporting metrics                             subtask=-1 task=DevLoop
DEBU[0001] metrics uploading complete in 800.135893ms    subtask=-1 task=DevLoop

[nkubala]

@sbienkow-ninja thanks for the issue. this looks like an issue with moby/buildkit, which we're using to validate Dockerfiles before parsing them as part of our cache check. I opened moby/buildkit#2436 - if/when that gets fixed we'll pick up the patch for the following skaffold release.

[lsoica]

This is still an issue with skaffold although in buildkit it was addressed long time back