We have a docker-compose.yml that specifies a build argument that is pulled from a boolean environment variable of false, but is explicitly quoted in docker-compose.yml.

When running a build with docker buildx bake we receive an error that the argument must be a string, number of null

Below is a minimal reproducible example that outlines the issue:

Dockerfile

FROM centos:8

ARG TEST_BOOLEAN
RUN echo $TEST_BOOLEAN

docker-compose.yml

version: '3.2'

services:
  app:
    image: "test-boolean"
    restart: always
    user: root
    build:
      context: .
      dockerfile: Dockerfile
      args:
        TEST_BOOLEAN: "${TEST_BOOLEAN}"

If we set export TEST_BOOLEAN=false and then run docker buildx bake it fails with the below:

[+] Building 0.0s (0/0)
error: services.app.build.args.TEST_BOOLEAN must be a string, number or null

This is the same if we export it as false, 'false' or "false".

Exporting export TEST_BOOLEAN='"false"' appears to work.

If we instead change docker-compose.yml to hardcode the false value (rather than pull from env var) as per below, the build succeeds:

version: '3.2'

services:
  app:
    image: "test-boolean"
    restart: always
    user: root
    build:
      context: .
      dockerfile: Dockerfile
      args:
        TEST_BOOLEAN: "false"

We are seeing the error on buildx version 0.6.3. On an older version, 0.5.1, the issue is not present

Perhaps related to either https://github.com/docker/buildx/pull/669/files or https://github.com/docker/buildx/pull/704/files