|
| 1 | +# Dev Container Features: Self Authoring Template |
| 2 | + |
| 3 | +> This repo provides a starting point and example for creating your own custom [dev container Features](https://containers.dev/implementors/features/), hosted for free on GitHub Container Registry. The example in this repository follows the [dev container Feature distribution specification](https://containers.dev/implementors/features-distribution/). |
| 4 | +> |
| 5 | +> To provide feedback to the specification, please leave a comment [on spec issue #70](https://github.com/devcontainers/spec/issues/70). For more broad feedback regarding dev container Features, please see [spec issue #61](https://github.com/devcontainers/spec/issues/61). |
| 6 | +
|
| 7 | +## Example Contents |
| 8 | + |
| 9 | +This repository contains a _collection_ of two Features - `hello` and `color`. These Features serve as simple feature implementations. Each sub-section below shows a sample `devcontainer.json` alongside example usage of the Feature. |
| 10 | + |
| 11 | +### `hello` |
| 12 | + |
| 13 | +Running `hello` inside the built container will print the greeting provided to it via its `greeting` option. |
| 14 | + |
| 15 | +```jsonc |
| 16 | +{ |
| 17 | + "image": "mcr.microsoft.com/devcontainers/base:ubuntu", |
| 18 | + "features": { |
| 19 | + "ghcr.io/devcontainers/feature-starter/hello:1": { |
| 20 | + "greeting": "Hello" |
| 21 | + } |
| 22 | + } |
| 23 | +} |
| 24 | +``` |
| 25 | + |
| 26 | +```bash |
| 27 | +$ hello |
| 28 | + |
| 29 | +Hello, user. |
| 30 | +``` |
| 31 | + |
| 32 | +### `color` |
| 33 | + |
| 34 | +Running `color` inside the built container will print your favorite color to standard out. |
| 35 | + |
| 36 | +```jsonc |
| 37 | +{ |
| 38 | + "image": "mcr.microsoft.com/devcontainers/base:ubuntu", |
| 39 | + "features": { |
| 40 | + "ghcr.io/devcontainers/feature-starter/color:1": { |
| 41 | + "favorite": "green" |
| 42 | + } |
| 43 | + } |
| 44 | +} |
| 45 | +``` |
| 46 | + |
| 47 | +```bash |
| 48 | +$ color |
| 49 | + |
| 50 | +my favorite color is green |
| 51 | +``` |
| 52 | + |
| 53 | +## Repo and Feature Structure |
| 54 | + |
| 55 | +Similar to the [`devcontainers/features`](https://github.com/devcontainers/features) repo, this repository has a `src` folder. Each Feature has its own sub-folder, containing at least a `devcontainer-feature.json` and an entrypoint script `install.sh`. |
| 56 | + |
| 57 | +``` |
| 58 | +├── src |
| 59 | +│ ├── hello |
| 60 | +│ │ ├── devcontainer-feature.json |
| 61 | +│ │ └── install.sh |
| 62 | +│ ├── color |
| 63 | +│ │ ├── devcontainer-feature.json |
| 64 | +│ │ └── install.sh |
| 65 | +| ├── ... |
| 66 | +│ │ ├── devcontainer-feature.json |
| 67 | +│ │ └── install.sh |
| 68 | +... |
| 69 | +``` |
| 70 | + |
| 71 | +An [implementing tool](https://containers.dev/supporting#tools) will composite [the documented dev container properties](https://containers.dev/implementors/features/#devcontainer-feature-json-properties) from the feature's `devcontainer-feature.json` file, and execute in the `install.sh` entrypoint script in the container during build time. Implementing tools are also free to process attributes under the `customizations` property as desired. |
| 72 | + |
| 73 | +### Options |
| 74 | + |
| 75 | +All available options for a Feature should be declared in the `devcontainer-feature.json`. The syntax for the `options` property can be found in the [devcontainer Feature json properties reference](https://containers.dev/implementors/features/#devcontainer-feature-json-properties). |
| 76 | + |
| 77 | +For example, the `color` feature provides an enum of three possible options (`red`, `gold`, `green`). If no option is provided in a user's `devcontainer.json`, the value is set to "red". |
| 78 | + |
| 79 | +```jsonc |
| 80 | +{ |
| 81 | + // ... |
| 82 | + "options": { |
| 83 | + "favorite": { |
| 84 | + "type": "string", |
| 85 | + "enum": [ |
| 86 | + "red", |
| 87 | + "gold", |
| 88 | + "green" |
| 89 | + ], |
| 90 | + "default": "red", |
| 91 | + "description": "Choose your favorite color." |
| 92 | + } |
| 93 | + } |
| 94 | +} |
| 95 | +``` |
| 96 | + |
| 97 | +Options are exported as Feature-scoped environment variables. The option name is captialized and sanitized according to [option resolution](https://containers.dev/implementors/features/#option-resolution). |
| 98 | + |
| 99 | +```bash |
| 100 | +#!/bin/bash |
| 101 | + |
| 102 | +echo "Activating feature 'color'" |
| 103 | +echo "The provided favorite color is: ${FAVORITE}" |
| 104 | + |
| 105 | +... |
| 106 | +``` |
| 107 | + |
| 108 | +## Distributing Features |
| 109 | + |
| 110 | +### Versioning |
| 111 | + |
| 112 | +Features are individually versioned by the `version` attribute in a Feature's `devcontainer-feature.json`. Features are versioned according to the semver specification. More details can be found in [the dev container Feature specification](https://containers.dev/implementors/features/#versioning). |
| 113 | + |
| 114 | +### Publishing |
| 115 | + |
| 116 | +> NOTE: The Distribution spec can be [found here](https://containers.dev/implementors/features-distribution/). |
| 117 | +> |
| 118 | +> While any registry [implementing the OCI Distribution spec](https://github.com/opencontainers/distribution-spec) can be used, this template will leverage GHCR (GitHub Container Registry) as the backing registry. |
| 119 | +
|
| 120 | +Features are meant to be easily sharable units of dev container configuration and installation code. |
| 121 | + |
| 122 | +This repo contains a **GitHub Action** [workflow](.github/workflows/release.yaml) that will publish each Feature to GHCR. |
| 123 | + |
| 124 | +*Allow GitHub Actions to create and approve pull requests* should be enabled in the repository's `Settings > Actions > General > Workflow permissions` for auto generation of `src/<feature>/README.md` per Feature (which merges any existing `src/<feature>/NOTES.md`). |
| 125 | + |
| 126 | +By default, each Feature will be prefixed with the `<owner/<repo>` namespace. For example, the two Features in this repository can be referenced in a `devcontainer.json` with: |
| 127 | + |
| 128 | +``` |
| 129 | +ghcr.io/devcontainers/feature-starter/color:1 |
| 130 | +ghcr.io/devcontainers/feature-starter/hello:1 |
| 131 | +``` |
| 132 | + |
| 133 | +The provided GitHub Action will also publish a third "metadata" package with just the namespace, eg: `ghcr.io/devcontainers/feature-starter`. This contains information useful for tools aiding in Feature discovery. |
| 134 | + |
| 135 | +'`devcontainers/feature-starter`' is known as the feature collection namespace. |
| 136 | + |
| 137 | +### Marking Feature Public |
| 138 | + |
| 139 | +Note that by default, GHCR packages are marked as `private`. To stay within the free tier, Features need to be marked as `public`. |
| 140 | + |
| 141 | +This can be done by navigating to the Feature's "package settings" page in GHCR, and setting the visibility to 'public`. The URL may look something like: |
| 142 | + |
| 143 | +``` |
| 144 | +https://github.com/users/<owner>/packages/container/<repo>%2F<featureName>/settings |
| 145 | +``` |
| 146 | + |
| 147 | +<img width="669" alt="image" src="https://user-images.githubusercontent.com/23246594/185244705-232cf86a-bd05-43cb-9c25-07b45b3f4b04.png"> |
| 148 | + |
| 149 | +### Adding Features to the Index |
| 150 | + |
| 151 | +If you'd like your Features to appear in our [public index](https://containers.dev/features) so that other community members can find them, you can do the following: |
| 152 | + |
| 153 | +* Go to [github.com/devcontainers/devcontainers.github.io](https://github.com/devcontainers/devcontainers.github.io) |
| 154 | + * This is the GitHub repo backing the [containers.dev](https://containers.dev/) spec site |
| 155 | +* Open a PR to modify the [collection-index.yml](https://github.com/devcontainers/devcontainers.github.io/blob/gh-pages/_data/collection-index.yml) file |
| 156 | + |
| 157 | +This index is from where [supporting tools](https://containers.dev/supporting) like [VS Code Dev Containers](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers) and [GitHub Codespaces](https://github.com/features/codespaces) surface Features for their dev container creation UI. |
| 158 | + |
| 159 | +#### Using private Features in Codespaces |
| 160 | + |
| 161 | +For any Features hosted in GHCR that are kept private, the `GITHUB_TOKEN` access token in your environment will need to have `package:read` and `contents:read` for the associated repository. |
| 162 | + |
| 163 | +Many implementing tools use a broadly scoped access token and will work automatically. GitHub Codespaces uses repo-scoped tokens, and therefore you'll need to add the permissions in `devcontainer.json` |
| 164 | + |
| 165 | +An example `devcontainer.json` can be found below. |
| 166 | + |
| 167 | +```jsonc |
| 168 | +{ |
| 169 | + "image": "mcr.microsoft.com/devcontainers/base:ubuntu", |
| 170 | + "features": { |
| 171 | + "ghcr.io/my-org/private-features/hello:1": { |
| 172 | + "greeting": "Hello" |
| 173 | + } |
| 174 | + }, |
| 175 | + "customizations": { |
| 176 | + "codespaces": { |
| 177 | + "repositories": { |
| 178 | + "my-org/private-features": { |
| 179 | + "permissions": { |
| 180 | + "packages": "read", |
| 181 | + "contents": "read" |
| 182 | + } |
| 183 | + } |
| 184 | + } |
| 185 | + } |
| 186 | + } |
| 187 | +} |
| 188 | +``` |
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