VS Code Docker: cannot build from local images

当你的 Dockerfile 是 FROM 一个 local image，然后你在 VS Code 里右键你的 Dockerfile 再 Build Image...，你可能会看到这样一个 error:

> Executing task in folder foo_vscode_ws: docker build --pull --rm -f "Dockerfile" -t foo-test:0.10.x "test-docker" <

[+] Building 1.3s (4/4) FINISHED                                         
 => [internal] load build definition from Dockerfile                0.0s
 => => transferring dockerfile: 37B                                 0.0s
 => [internal] load .dockerignore                                   0.0s
 => => transferring context: 2B                                     0.0s
 => ERROR [internal] load metadata for docker.io/library/foo  1.2s
 => [auth] library/foo:pull token for registry-1.dock  0.0s
------
 > [internal] load metadata for docker.io/library/foo:0.10.x:
------
failed to solve with frontend dockerfile.v0: failed to create LLB definition: pull access denied, repository does not exist or may require authorization: server message: insufficient_scope: authorization failed
The terminal process "zsh '-c', 'docker build --pull --rm -f "Dockerfile" -t foo-test:0.10.x "test-docker"'" terminated with exit code: 1.

Terminal will be reused by tasks, press any key to close it.

你会发现自己 terminal 跑一个 docker build -f Dockerfile -t foo:0.10.x 是完全没问题的，说明这完全是 VS Code 的 Docker plugin 自己的问题。问题就出在它 Build Image... 命令默认会有一个参数 --pull:

--pull Always attempt to pull a newer version of the image

也就是说它会 pull from docker hub，所以当你是 FROM 一个 local image 的时候，这个 Build Image... 命令肯定是会 fail.

这个问题已经有人反映过了，参见 Build image forces “–pull”, makes local development inconvenient。解决方案这个 issue 也写了，参见 Command customization:

{
  "docker.commands.build": [
    {
      "label": "Default build command",
      "template": "docker build --rm -f \"${dockerfile}\" -t ${tag} \"${context}\""
    },
    {
      "label": "Alpine-specific build command",
      "template": "docker build -p 1234:1234 -f \"${dockerfile}\" -t ${tag} \"${context}\"",
      "match": "alpine"
    },
    {
      "label": "Context-specific build command",
      "template": "docker build -f \"${dockerfile}\" .",
      "contextTypes": ["moby"]
    }
  ]
}

一旦你定义了多个 command label，下次 Build Image... 就会弹出一个 list 让你选择具体是要跑哪个 command.