Inconsistent `pull_policy` behavior with `docker compose` when combining build and image

.devcontainer/devcontainer.json と compose.yml を使用し、@devcontainers/cli up --workspace-folder .. で動作を再現します。まず、このエントリーポイントが image と build の両方を定義するサービスをどのように処理するかを追跡し、次に生成された docker compose コマンドを、文書化されている pull_policy の動作と比較します。イメージを pull するかキャッシュ内で見つけるべき場合に、デフォルトのワークフローが db に対して docker compose build を実行しなければ完了です。

https://docs.docker.com/reference/compose-file/build/#using-build-and-image

https://docs.docker.com/reference/compose-file/services/#image

Using build and image
When Compose is confronted with both a build subsection for a service and an image attribute, it follows the rules defined by the pull_policy attribute.

If pull_policy is missing from the service definition, Compose attempts to pull the image first and then builds from source if the image isn't found in the registry or platform cache.

i.e. by default it should pull image from registry/cache before attempting to build when using docker compose up, therefore I expect

.devcontainer/devcontainer.json --- JSON
 1 
 2 {
 3     "name": "Repro",
 4     "dockerComposeFile": "../compose.yml",
 5     "service": "devcontainer",
 6     "workspaceFolder": ".",
 7     "runServices": [
 8         "db"
 9     ]
10 }
11 

compose.yml --- YAML
 1 services:
 2   devcontainer:
 3     image: mcr.microsoft.com/devcontainers/base:ubuntu
 4     volumes:
 5       - ../..:/workspaces:cached
 6     network_mode: service:db
 7     command: sleep infinity
 8 
 9   db:
10     image: postgres:latest
11     build:
12       context: .
13       dockerfile_inline: |
14         FROM postgres:latest
15     restart: unless-stopped
16     volumes:
17       - postgres-data:/var/lib/postgresql/data
18     environment:
19       POSTGRES_PASSWORD: postgres
20       POSTGRES_USER: postgres
21       POSTGRES_DB: postgres
22 
23 volumes:
24   postgres-data:
25 

(output from git diff)

to not run docker compose build db when running @devcontainers/cli up --workspace-folder .

But it currently runs docker compose --project-name devcontainer-repro -f <abbreviated-path>/devcontainer-repro/compose.yml build db devcontainer

Why this matters:

When trying to prebuild/cache images it is beneficial to have one compose.yml which both defines the image and how to build the image, otherwise you need to split the file in two compose.build.yml and compose.yml. This behavior is inconsistent and confusing.