Add experimental Dev Container support to Positron (#10884)

This change adds early, experimental support for Dev Containers to
Positron.

<img width="1226" height="860" alt="image"
src="https://github.com/user-attachments/assets/e0ca3360-12c9-47da-93c6-cade37db47a4"
/>

Because the feature is experimental, it is currently behind a feature
flag:

<img width="578" height="136" alt="image"
src="https://github.com/user-attachments/assets/fd2495e9-dc88-436a-a0c7-035bf75623fa"
/>

The goal of this change is to enable the most common dev container
workflows that center around building (or rebuilding) a container and
opening the workspace inside the container. However, note that in this
early version, many features are not implemented or are incomplete.
Specifically:

- musl-based Linux distributions (such as Alpine) are not supported
(#10468); the container must be running a version of Linux already
supported by Positron
- Only single-container configurations are supported (no `docker
compose`)
- No tools or templates are supplied for creating or authoring
`devcontainer.json` files
- Only one container is supported per project
- Docker volumes are not supported, just regular mounts
- In the MRU, dev containers show up with the remote rather than local
path (e.g. `/workspaces/foo`)
- Container management features (see/attach to running containers) are
not available when inside a container

For compatibility, the new extension uses largely the same command names
and settings as the official VS Code Dev Containers extension.

It also includes a lightly modified version of the [Dev Containers
CLI](https://github.com/devcontainers/cli) reference implementation. The
implementation is used to derive the correct container management
commands, which are (generally) executed in Positron terminals for
visibility.

Addresses #4691. 



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#### New Features

- Experimental support for Dev Containers (#4691)

#### Bug Fixes

- N/A


### QA Notes

Like Remote SSH, this feature is difficult to test outside release
builds since it needs to download a matching server component into the
container. And -- also like remote SSH -- there's a setting to change
the download URL. If you need to test a build that doesn't have a
released Positron version to download, you can change this setting to
the URL of the closest matching build.

This feature should be tested across all three operating systems since
the Docker integration is somewhat OS-specific.

---------

Co-authored-by: positron-bot[bot] <173392469+positron-bot[bot]@users.noreply.github.com>

Author: jmcphers

build/gulpfile.extensions.js

@@ -34,6 +34,7 @@ const compilations = [
 	'extensions/positron-catalog-explorer/tsconfig.json',
 	'extensions/positron-code-cells/tsconfig.json',
 	'extensions/positron-connections/tsconfig.json',
+	'extensions/positron-dev-containers/tsconfig.json',
 	'extensions/positron-duckdb/tsconfig.json',
 	'extensions/positron-environment/tsconfig.json',
 	'extensions/positron-ipywidgets/renderer/tsconfig.json',

build/npm/dirs.js

@@ -17,6 +17,7 @@ const dirs = [
 	'extensions/positron-code-cells',
 	'extensions/positron-copilot-chat',
 	'extensions/positron-connections',
+	'extensions/positron-dev-containers',
 	'extensions/positron-duckdb',
 	'extensions/positron-environment',
 	'extensions/positron-ipywidgets',

extensions/positron-dev-containers/README.md

@@ -0,0 +1,109 @@
+# Dev Containers Extension for Positron
+
+## Overview
+
+The Dev Containers extension enables you to open any folder or repository inside a Docker container and take advantage of Positron's full feature set within that containerized environment. This allows you to define your project's dependencies declaratively, install them in a lightweight container, and run the entire project inside the container with a consistent, reproducible development environment.
+
+For compatibility with VS Code, this extension uses most of the same command IDs and setting names from VS Code's version of the extension. The extension itself is novel code, with the exception of the contents of the `spec` folder, which is adapted from the MIT-licensed [dev container reference implementation](https://github.com/devcontainers/cli).
+
+## Requirements
+
+- Docker or Podman installed and running
+- A workspace with a `.devcontainer.json` or `.devcontainer/devcontainer.json` file
+
+## Configuration
+
+Enable the extension in your settings:
+
+```json
+{
+  "dev.containers.enable": true
+}
+```
+
+## Usage
+
+### Opening a Folder in a Container
+
+1. Open a folder that contains a `.devcontainer.json` file
+2. Click the notification prompt, or
+3. Use the command palette: **Dev Containers: Reopen in Container**
+
+### Attaching to a Running Container
+
+1. Open the Remote Explorer view
+2. Expand the "Dev Containers" section
+3. Right-click a running container and select "Attach in Current Window" or "Attach in New Window"
+
+### Rebuilding a Container
+
+When you've made changes to your `devcontainer.json` or `Dockerfile`:
+
+- **Dev Containers: Rebuild Container** - Rebuild using cache
+- **Dev Containers: Rebuild Without Cache** - Full rebuild from scratch
+- **Dev Containers: Rebuild and Reopen in Container** - Rebuild and automatically reopen
+
+### Key Components
+
+#### Extension Entry Point (`extension.ts`)
+- Activates the extension when enabled
+- Registers commands, views, and authority resolvers
+- Initializes core managers and services
+- Handles pending rebuild requests
+
+#### Remote Authority Resolver (`remote/authorityResolver.ts`)
+- Resolves `dev-container://` and `attached-container://` URIs
+- Manages connections to containers
+- Handles workspace folder resolution
+- Implements VS Code's remote development protocol
+
+#### Connection Manager (`remote/connectionManager.ts`)
+- Manages active connections to containers
+- Tracks connection state and lifecycle
+- Handles connection failures and recovery
+- Coordinates with port forwarding
+
+#### Dev Container Manager (`container/devContainerManager.ts`)
+- Creates and starts containers from `devcontainer.json`
+- Handles container building and rebuilding
+- Manages container lifecycle (start, stop, remove)
+- Retrieves container information and logs
+
+#### Server Installer (`server/serverInstaller.ts`)
+- Downloads the Positron server for the container platform
+- Installs and configures the server inside containers
+- Generates connection tokens for secure communication
+- Handles server updates and versioning
+
+#### Workspace Mapping Storage (`common/workspaceMappingStorage.ts`)
+- Persists mappings between container IDs and workspace paths
+- Enables proper workspace resolution across window reloads
+- Provides cleanup for stale mappings
+
+#### Dev Container Reference CLI (spec/)
+- Copy of the Microsoft Dev Container Reference CLI
+- Used to manage containers and form Docker commands
+
+### Remote Development Flow
+
+The workflow typically looks like this;
+
+1.  User invokes "Reopen in Container"
+2.  Extension reads `devcontainer.json` and creates/starts container
+3.  Positron server is downloaded and installed in container
+4.  VS Code resolves the remote authority and establishes connection
+5.  Extension maps local paths to container paths
+6.  Necessary ports are forwarded from container to host
+7.  User can now work with code inside the container
+
+## Known Limitations
+
+- Requires glibc-based Linux since Positron Server builds of Linux require glibc (e.g. Alpine will not work)
+- Doesn't support "Create from template"; you need to create Dockerfiles / devcontainer JSON files by hand
+- Doesn't support development volumes (popular feature from VS Code's implementation, used for e.g. faster I/O)
+- Container management views and features are not available if you are inside a container/remote
+- Currently experimental and requires explicit enablement
+- Requires Docker or Podman to be installed and running
+- GPU support is platform-dependent
+- Some features have limited support in containers
+

extensions/positron-dev-containers/extension.webpack.config.js

@@ -0,0 +1,17 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (C) 2025 Posit Software, PBC. All rights reserved.
+ *  Licensed under the Elastic License 2.0. See LICENSE.txt for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+//@ts-check
+
+'use strict';
+
+const withDefaults = require('../shared.webpack.config.mjs').default;
+
+module.exports.default = withDefaults({
+	context: __dirname,
+	entry: {
+		extension: './src/extension.ts',
+	}
+});