# Dev Containers A *container* refers to an isolated area of memory where application software and some drivers execute. A [Development Container](https://containers.dev) (or Dev Container for short) allows a container to be used as a full‑featured development environment. Stack provides the following Dev Containers: * a default Dev Container, intended for use with Stack's default project‑level configuration file (`stack.yaml`); and * alternative Dev Containers, intended for use with Stack's experimental project‑level configurations (in anticipation of building Stack with more recent versions of GHC). Stack's Dev Containers provide the following tools: 1. The [Haskell Toolchain](https://www.haskell.org/ghcup/install/#supported-tools) ([GHC](https://www.haskell.org/ghc), Stack, [Cabal (the tool)](https://cabal.readthedocs.io) and [HLS](https://haskell-language-server.readthedocs.io)) 2. [Git](https://git-scm.com) 3. [HLint](https://hackage.haskell.org/package/hlint) 4. [yamllint](https://yamllint.readthedocs.io) 5. [ShellCheck](https://www.shellcheck.net) 6. [hadolint](https://github.com/hadolint/hadolint) The tools in the Haskell Toolchain are installed at `/usr/local/bin`. HLS is provided in the default Dev Container only. !!! info The PATH is `$HOME/.cabal/bin:$HOME/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin`. Consequently, executables installed with Cabal (the tool) (at `$HOME/.cabal/bin` or `$HOME/.local/bin`) or Stack or Pip (at `$HOME/.local/bin`) take precedence over the same executable installed at `/usr/local/sbin`, `/usr/local/bin`, etc. [VS Code](https://code.visualstudio.com) is used as IDE, with the following extensions pre‑installed: * [Haskell](https://marketplace.visualstudio.com/items?itemName=haskell.haskell) (Default Dev Container only) * [GitHub Pull Requests and Issues](https://marketplace.visualstudio.com/items?itemName=GitHub.vscode-pull-request-github) * [GitLens — Git supercharged](https://marketplace.visualstudio.com/items?itemName=eamodio.gitlens) * Pinned to version 11.7.0 due to unsolicited AI content in recent versions * [Git Graph](https://marketplace.visualstudio.com/items?itemName=mhutchie.git-graph) * [ShellCheck](https://marketplace.visualstudio.com/items?itemName=timonwong.shellcheck) * [hadolint](https://marketplace.visualstudio.com/items?itemName=exiasr.hadolint) * [Resource Monitor](https://marketplace.visualstudio.com/items?itemName=mutantdino.resourcemonitor) ## Parent images Stack's Dev Containers are derived from Docker images that are used to build the *statically linked* Linux/x86_64 and Linux/AArch64 binary distributions of Stack. These Docker images are multi‑architecture (`linux/amd64`, `linux/arm64/v8`) *GHC musl* images. They are based on Alpine Linux (that is [musl libc](https://musl.libc.org) and [BusyBox](https://www.busybox.net)). The images contain *unofficial* binary distributions of GHC (that is, ones not released by the GHC developers). That is because: 1. the official GHC binary distributions for Alpine Linux/x86_64 have known bugs; and 2. there are no official binary distributions for Alpine Linux/AArch64. Stack's global configuration (`/etc/stack/config.yaml`) sets `system-ghc: true` and `install-ghc: false`. That ensures that only the GHC available in the Dev Containers is used. ## Usage You can run Dev Containers locally/remotely with VS Code, or create a [GitHub Codespace](https://github.com/features/codespaces) for a branch in a repository to develop online. === "VS Code" Follow the instructions at [Developing inside a Container](https://code.visualstudio.com/docs/devcontainers/containers). === "GitHub Codespaces" For use with GitHub Codespaces, follow the instructions at [Creating a codespace for a repository](https://docs.github.com/en/codespaces/developing-in-codespaces/creating-a-codespace-for-a-repository#creating-a-codespace-for-a-repository). ## Build Stack Stack can be built with Stack (which is recommended) or with Cabal (the tool). === "Stack" Command `stack build` to build the `stack` executable. Append `--flag=stack:static` to build a *statically linked* `stack` executable that can run on any Linux machine of the same architecture. Append `--stack-yaml stack-ghc-$GHC_VERSION.yaml` if you want to use an experimental project‑level configuration with the appropriate Dev Container. === "Cabal (the tool)" !!! info Default Dev Container only. Command `cabal build` to build the `stack` executable. Append `--flag=static` to build a *statically linked* `stack` executable that can run on any Linux machine of the same architecture. ## Haskell Language Server (HLS) The [Haskell Language Server](https://github.com/haskell/haskell-language-server) and the [Haskell extension](https://marketplace.visualstudio.com/items?itemName=haskell.haskell) are only available in the default Dev Container. In order to use the Haskell extension, you must first configure the project for the build tool of your choice. See the documentation at [Contributing: Haskell Language Server](CONTRIBUTING.md#haskell-language-server) for cradles (`hie.yaml` files) that should suffice to configure the HLS explicitly for `./Setup.hs` and each of the buildable components in Stack's Cabal file. ### Haskell extension Choose `Manually via PATH` when asked the following question: ## Issues If there is a problem with a Dev Container, please [open an issue](https://github.com/benz0li/ghc-musl/issues/new) at its [parent images](#parent-images)' repository at [https://github.com/benz0li/ghc-musl](https://github.com/benz0li/ghc-musl).