# dev_container: Handle devcontainer.metadata label as JSON object or array \(\#53557\) · gitcafe/zed

[View on GitCafe](https://git.cafe/gitcafe/zed/commit/2d3f49e4b265c6d074b0d3316806a454fccabeb8)

Repository: [gitcafe/zed](https://git.cafe/gitcafe/zed)

Visibility: public

Requested revision: 2d3f49e4b265c6d074b0d3316806a454fccabeb8

Requested commit: 2d3f49e4b265c6d074b0d3316806a454fccabeb8

Commit: 2d3f49e4b265c6d074b0d3316806a454fccabeb8

Tree: 8f6a159435cacb69f9913f0b1c9f51f03970f439

Author: Sandro Meier

Committer: GitHub

## Message

````
dev_container: Handle devcontainer.metadata label as JSON object or array (#53557)

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] 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

## Details

- The [devcontainer CLI writes the `devcontainer.metadata` label as a
bare JSON object](https://github.com/devcontainers/cli/issues/1054) when
there is only one metadata entry (e.g. docker-compose devcontainer with
a Dockerfile and no features)
- Zed's `deserialize_metadata` only accepted a JSON array, causing
deserialization to fail with `invalid type: map, expected a sequence`
- This made it impossible to attach to existing docker-compose
devcontainers created by the devcontainer CLI or VS Code

The fix tries parsing as an array first, then falls back to parsing as a
single object wrapped in a vec. This mirrors how the [devcontainer CLI
itself reads the
label](https://github.com/devcontainers/cli/blob/main/src/spec-node/imageMetadata.ts#L476-L493).

An upstream fix has also been submitted:
https://github.com/devcontainers/cli/pull/1199

## Reproduction

1. Create a docker-compose devcontainer with a Dockerfile and no
features:

`.devcontainer/devcontainer.json`:
```json
{
  "name": "repro",
  "dockerComposeFile": "docker-compose.yml",
  "service": "app",
  "remoteUser": "root"
}
```

`.devcontainer/docker-compose.yml`:
```yaml
services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
    command: sleep infinity
    volumes:
      - ..:/workspace
```

`.devcontainer/Dockerfile`:
```dockerfile
FROM ubuntu:24.04
```

2. `devcontainer up --workspace-folder .`
3. Open the folder in Zed, fails with metadata deserialization error

Release Notes:

- Fixed attaching to a devcontainer that has a single metadata element
which was started with `devcontainer-cli`
````

## Parents

- [5a9f82583bdaf9a41676b23cf2d00d878beb4b09](https://git.cafe/gitcafe/zed/commit/5a9f82583bdaf9a41676b23cf2d00d878beb4b09?format=markdown)

[Source at this commit](https://git.cafe/gitcafe/zed/tree/2d3f49e4b265c6d074b0d3316806a454fccabeb8?format=markdown)