Create a Development Container Feature for Dev Proxy

[garrytrinder]

To make it easier for developers to integrate Dev Proxy into GitHub Codespaces and VS Code Dev Containers, we should create a Development Container Feature for Dev Proxy.

Benefits of this approach:

• Streamlined setup: Developers can enable Dev Proxy with a single line of configuration in their devcontainer.json, avoiding manual installation steps.
• Consistency: Ensures consistent Dev Proxy installation and configuration across different environments and teams.
• Reusability: The feature can be reused across multiple dev containers and projects, reducing duplicate effort.
• Discoverability: Features are listed in the Dev Container Feature marketplace, making Dev Proxy easier to find and adopt.
• Best practices: Follows the recommended approach for extensibility in Codespaces and Dev Containers.

A GitHub repository template is available to author the feature: @devcontainers/feature-starter

VSCode Docs: Dev Container Features

[waldekmastykarz]

Cool idea! Let's spec it out some more so that we know what we'd like to have.

[waldekmastykarz]

Here's a proposed spec for the Dev Container Feature.

What it should do

A Dev Container Feature that installs and configures Dev Proxy in a dev container or GitHub Codespace with minimal configuration.

Proposed devcontainer.json usage

{
  "features": {
    "ghcr.io/dotnet/dev-proxy/devproxy:1": {
      "version": "latest",
      "trustCertificate": true
    }
  }
}

Feature options

Option	Type	Default	Description
version	string	"latest"	Dev Proxy version to install (e.g., "v2.2.0")
trustCertificate	boolean	true	Automatically run devproxy cert ensure and trust the root CA certificate in the container

Installation steps (in install.sh)

1. Download Dev Proxy release for the container's architecture (reuse logic from our existing scripts/setup.sh)
2. Extract to /usr/local/bin/devproxy or /opt/devproxy and add to PATH
3. If trustCertificate is true, run devproxy cert ensure to generate and trust the SSL certificate
4. Verify installation with devproxy --version

Repository and hosting

• Use the @devcontainers/feature-starter template
• Host as a separate repo (e.g., dotnet/dev-proxy-devcontainer-feature) or under a features/ folder in this repo
• Publish to GHCR for discoverability in the Dev Container Feature marketplace

Testing considerations

• Test on Debian/Ubuntu-based images (most common for Codespaces)
• Test with both x64 and arm64 architectures
• Verify cert trust works for .NET apps, Node.js apps, and Python apps (different cert stores)
• Related to Research the end-to-end user experience of using Dev Proxy in a GitHub Codespace (as an app developer) #1289 — the Codespace UX research should validate this feature's design

Open questions

• Should we scope this to just installation, or also include proxy auto-start capabilities?
• Should the feature set up environment variables like HTTP_PROXY/HTTPS_PROXY automatically?
• Separate repo vs. subfolder in this repo?

[garrytrinder]

We should also include Dev Proxy Toolkit in the devcontainer

"customizations": {
    "vscode": {
      "extensions": ["garrytrinder.dev-proxy-toolkit"]
    }
  },