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

Riproduci il comportamento con .devcontainer/devcontainer.json e compose.yml usando @devcontainers/cli up --workspace-folder .. Inizia tracciando il modo in cui questo punto di ingresso gestisce i servizi che definiscono sia image sia build, quindi confronta il comando docker compose generato con il comportamento documentato di pull_policy. Il lavoro è completato quando il workflow predefinito non esegue docker compose build per db quando l’immagine deve essere scaricata o trovata nella cache.

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.