Error building docker image for different platform/arch on M1 mac

Problem occured when building linux/amd64 image (by setting platform parameter) on M1 mac for different arch. I isolated a case for this bug and found workaround.

The problem is when building an image which has:

• scratch as a base image
• platform different than current platform, e.g. building 'linux/amd64' image on M1 mac, or building 'linux/arm64' image on amd64 machine (I tested both cases)
• ARG as the first operation

The problem does not occur when the base image is changed to anything else (e.g. ubuntu), or platform switch is not set, or there is different first op than ARG.

Build fails from code
Dockerfile:

FROM scratch
ARG dummy_arg
ADD file2.txt /data/file2.txt

Run with code:

client = docker.client.from_env()
_, _ = client.images.build(path="context", dockerfile="Dockerfile", tag="test-image", platform="linux/amd64", nocache=True)

Results in:

DEBUG:docker.api.build:Looking for auth config
DEBUG:docker.api.build:Sending auth config ()
DEBUG:urllib3.connectionpool:http://localhost:None "POST /v1.41/build?t=test-image-3494&q=False&nocache=True&rm=False&forcerm=False&pull=False&dockerfile=Dockerfile&platform=linux%2Famd64 HTTP/1.1" 200 None
Traceback (most recent call last):
  File "/Users/lsierant/mdb/sonar-fix/test.py", line 11, in <module>
    _, _ = client.images.build(path="context", dockerfile="Dockerfile", tag=image_name, platform="linux/amd64", nocache=True)
  File "/Users/lsierant/mdb/sonar-fix/venv/lib/python3.9/site-packages/docker/models/images.py", line 285, in build
    raise BuildError(chunk['error'], result_stream)
docker.errors.BuildError: failed to get destination image "sha256:5b89a558a786c4b82412c56c53bfdf715817ab99cd7e63bd08b496a696060c36": image with reference sha256:5b89a558a786c4b82412c56c53bfdf715817ab99cd7e63bd08b496a696060c36 was found but does not match the specified platform: wanted linux/amd64, actual: linux/arm64```

Build succeeds from cli
The same dockerfile built from cli is working correctly.

$ docker build . --platform "linux/amd64" --no-cache -t test-image
[+] Building 0.1s (5/5) FINISHED
=> => transferring dockerfile: 36B
=> [internal] load .dockerignore
=> => transferring context: 2B
=> [internal] load build context                                                                                                                                                                              => => transferring context: 30B
=> [1/1] ADD file2.txt /data/file2.txt
=> exporting to image                                                                                                                                                                                         => => exporting layers
=> => writing image sha256:fb7f611c51c95f880cbeabf3a77067dafa8cd9cb961a6564bcba035fcc0ecef9
=> => naming to docker.io/library/test-image

Workaround
It seems that this error occurs only when having scratch image as a base and ARG as a second command. After swapping ARG and ADD lines the image is building. Also changing the base image to anything different than scratch is working.

FROM scratch
ADD file2.txt /data/file2.txt
ARG dummy_arg

Results in:

DEBUG:urllib3.connectionpool:http://localhost:None "POST /v1.41/build?t=test-image-5877&q=False&nocache=True&rm=False&forcerm=False&pull=False&dockerfile=Dockerfile.ok&platform=linux%2Famd64 HTTP/1.1" 200 None
DEBUG:urllib3.connectionpool:http://localhost:None "GET /v1.41/images/4491aba34a0f/json HTTP/1.1" 200 None

Steps to recreate
I created sample project when trying to pin down the issue: https://github.com/lsierant/playground-docker-py

1. git clone https://github.com/lsierant/playground-docker-py.git
2. ./run-test.sh (setups venv and runs test.py)

Environment
I tested it on M1 mac (building linux/arm64) and on linux machine building arm64 image.
pip freeze | grep docker && python --version && docker version

Python 3.9.13
Client:
 Cloud integration: v1.0.24
 Version:           20.10.14
 API version:       1.41
 Go version:        go1.16.15
 Git commit:        a224086
 Built:             Thu Mar 24 01:49:20 2022
 OS/Arch:           darwin/arm64
 Context:           default
 Experimental:      true

Server: Docker Desktop 4.8.2 (79419)
 Engine:
  Version:          20.10.14
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.16.15
  Git commit:       87a90dc
  Built:            Thu Mar 24 01:45:44 2022
  OS/Arch:          linux/arm64
  Experimental:     false
 containerd:
  Version:          1.5.11
  GitCommit:        3df54a852345ae127d1fa3092b95168e4a88e2f8
 runc:
  Version:          1.0.3
  GitCommit:        v1.0.3-0-gf46b6ba
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

Start with the reproducer's test.py and Dockerfile, then inspect client.images.build and compare its request with the successful docker build command. Use run-test.sh to reproduce the scratch-plus-ARG case on a different target platform; done means the Python client builds the image successfully with the same parameters.