This repository contains a minimal Emacs configuration to support Ada development, which includes the installation and configuration of packages for Ada and GNAT Project. This also includes the installation of LSP client packages eglot and lsp-mode. The specific LSP client to use is controlled in early-init.el. Emacs 29 is required in order to use the tree-sitter based packages included in this configuration.

Installation/Startup

The expectation is that this configuration will be used as an example configuration and not the user’s default configuration. Therefore, the following instructions place the configuration in a non-standard location and then specify that location when starting Emacs.

Note: If using ~/.emacs as your configuration file, use of --init-directory does not work as expected. Therefore, you’ll need to rename ~/.emacs so that the configuration in this repository can be used correctly.

git clone https://github.com/brownts/dotemacs-ada ~/.emacs-ada.d
emacs --init-directory=~/.emacs-ada.d

Once started, the packages identified in the configuration (i.e., init.el) will be downloaded from an ELPA and installed.

Tree-Sitter Language Library Binary Installation

By default, the tree-sitter library for Ada and GPR will be downloaded and built from source when the major mode is loaded. If you’d prefer to install a pre-built language library instead, you can obtain these from the following location:

• https://github.com/casouri/tree-sitter-module/releases

If manually installing, the shard libraries should be placed in the tree-sitter directory beneath user-emacs-directory. If using the installation instructions above, that would be ~/.emacs-ada.d/tree-sitter/.

Configure Preferred LSP Client

To configure lsp-mode as the preferred LSP client, use the following in early-init.el:

(setq init.el/preferred-lsp-client 'lsp-mode)

To configure eglot as the preferred LSP client, use the following in early-init.el:

(setq init.el/preferred-lsp-client 'eglot)

Language Server Installation

The lsp-mode package includes the ability to install the Ada Language Server when lsp-mode is enabled in an Ada or GPR buffer. If the Ada Language Server is installed in this manner, it will be installed in the .cache/lsp/ada-ls directory beneath user-emacs-directory (e.g., ~/.emacs-ada.d/.cache/lsp/ada-ls/). If the Ada Language Server is found on the path, the server found there will be used instead. If desired, the Language Server can be installed manually by downloading it from the GitHub repository and placing it somewhere on the path.

The eglot package does not include the ability to install the Ada Language Server. There are two options for installation. The first option is to manually install the Ada Language Server somewhere on the path. The second option is to first use the lsp-mode package and let it install the server before changing init.el/preferred-lsp-client from lsp-mode to eglot and then restarting Emacs. The Emacs configuration in this repository will add lsp-mode’s Ada Language Server installation directory to Emacs’ exec-path so that a previous installation can be used by Eglot.

Example Usage (GtkAda)

The following example assumes the Alire tool (i.e., alr) is already installed. If not, visit alire.ada.dev to download and install it.

Obtain the GtkAda crate

alr get gtkada
cd gtkada*

Note: In the above alr get command, the GtkAda directory name will contain the version and a hash, thus the use of the wildcard when changing into that directory.

Create .dir-locals.el

Next, create a .dir-locals.el file with the following contents in the top-level directory of the GtkAda crate directory we just obtained:

((ada-ts-mode . ((lsp-ada-project-file . "src/gtkada.gpr")))
 ;; Eglot uses the first `major-mode' in `eglot-server-programs' for
 ;; the Language Server, therefore we have to use `ada-mode' here
 ;; instead of `ada-ts-mode'.  This seems like a bug!
 (ada-mode . ((eglot-workspace-configuration . (:ada (:projectFile "src/gtkada.gpr")))))
 (nil . ((compile-command . "alr build -- -gnatef"))))

It should be noted that lsp-ada-project-file is used by lsp-mode to inform the Ada Language Server the path to the project file. For Eglot, the same is performed by using the eglot-workspace-configuration and its associated property list. Refer to the Eglot Project-specific configuration, lsp-mode Ada Language configuration as well as the Ada Language Server Settings to learn about additional configuration options and the specific formatting of those options required by each LSP client.

Note: Technically it’s not necessary to specify the project file configuration in the .dir-locals.el if the Ada Language Server can find it in alire.toml, but the above is used to demonstrate how to manually configure the project file using either of the available Emacs LSP clients, if needed.

The compilation command is also specified here which is used whenever a compilation is performed (e.g., project-compile via C-x p c). Since this is an Alire project, an Alire build command is used.

Configure Source Code Formatting

In order to support LSP-based indentation, it is useful to add a Pretty_Printer section to the GPR file (i.e., in src/gtkada.gpr) and configure it so that the Language Server formatting engine does not significantly restructure the source.

package Pretty_Printer is
   for Default_Switches ("Ada") use ("--source-line-breaks");
end Pretty_Printer;

Use Emacs

Open any Ada or GPR file and enjoy! Performing a compilation within Emacs (C-x p c) will build the project using the compilation command specified in the .dir-locals.el file created earlier.

emacs --init-directory=~/.emacs-ada.d src/gtkada-application.adb