Files
Toru NayukiandGitHub 26fc42721a dev_container: Support the classic Docker builder via a setting (#59288)
Dev container image builds default to BuildKit (`docker buildx`).
Docker-compatible engines that lack an integrated BuildKit — notably
[Apple Container](https://github.com/apple/container) accessed through a
Docker-API bridge — cannot resolve a locally-built image in a `FROM`,
which breaks the dev container build: Zed builds the features image,
then a second `FROM <features-image>` build (the UID remap), and
BuildKit's docker-container/remote drivers can't see the daemon's local
image, failing with `pull access denied`.

The daemon's *classic* builder resolves locally-built images, and Zed
already generates a BuildKit-free Dockerfile for the non-BuildKit path
(multi-stage `FROM` + `COPY --from`, no `RUN --mount`). This wires that
path to a setting and makes the remaining build invocations actually use
the classic builder.

## Changes

- Add a `dev_container_use_buildkit` setting (tri-state):
- unset → auto-detect via the `docker buildx` plugin (current behavior)
  - `false` → force the classic builder
  - `true` → force BuildKit
- When the classic builder is selected, pass `DOCKER_BUILDKIT=0` (and
`COMPOSE_DOCKER_CLI_BUILD=0` for compose) to the feature-content build,
the compose build, and the UID-remap build, so multi-stage `FROM` of a
locally-built image resolves through the daemon's classic builder.
- Document the setting in `docs/src/dev-containers.md`.

With this setting plus a Docker-API bridge, a real Rails dev container
(compose: app + mysql + valkey, with features) builds and starts on
Apple Container.

## How to Review

- `settings_content.rs` / `dev_container/src/lib.rs` — the new setting
and its plumbing into `DevContainerContext`.
- `docker.rs` — `Docker::new` honors the setting
(`supports_compose_buildkit`), `docker_compose_build` selects the
classic builder; unit test
`use_buildkit_setting_overrides_buildx_detection`.
- `devcontainer_manifest.rs` — `DOCKER_BUILDKIT=0` for the
feature-content and UID-remap builds.

## Self-Review Checklist

- [x] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [ ] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Release Notes:

- Added a `dev_container_use_buildkit` setting to build dev containers
with the classic Docker builder for engines without an integrated
BuildKit (e.g. Apple Container)
2026-06-15 07:04:03 +00:00
..
2026-01-16 15:20:48 -08:00