Tree-Sitter parser for Ada

The grammar is adapted from the work done by Stephen Leak for the Emacs ada-mode. It was translated (partially for now) to tree-sitter syntax, and slightly changed to reduce some conflicts. Tree-sitter doesn't need a full syntax tree, so we can take some shortcuts in the grammar.

Installation

You will need neovim at least version 8.0 (not tested with earlier version).

Installation is very manual at this stage, until we can integrate this package inside nvim-treesitter itself. At the moment, assuming you are using lua configuration and Packer for your package management:

-- file: ~/.config/nvim/init.lua

--  Merge this with any existing Packer configuration you might already
--  have. This loads packer itself, then loads the new `ada.nvim` package.
require('packer').startup(function(use)
    use(require('mytreesitter.nvim'))
end)

Then create a new file to setup treesitter (or merge with an existing configuration of course).

--  file: ~/.config/nvim/mytreesitter.nvim

return {
   'nvim-treesitter/nvim-treesitter',
   requires = {
      'nvim-treesitter/nvim-treesitter-textobjects'
   },
   run=function()
      require('nvim-treesitter.install').update({ with_sync = true })
   end,
   config=function()

      --  Add support for our Ada parser

      local parsers = require "nvim-treesitter.parsers"
      local parser_config = parsers.get_parser_configs()
      parser_config.ada = {
         install_info = {
            url = "https://github.com/briot/tree-sitter-ada",
            files = {"src/parser.c"},
            generate_requires_npm = false,
            requires_generate_from_grammar = false,
         },
         filetype = "ada",
       }
   end,
}

Finally, we need to install the Ada parser with:

   :PackerSync                          " to install treesitter itself
   :TSInstall ada                       " to install Ada support

However, the above part only installs the parser itself (to generate a syntax tree from your source files). We now need to install queries, i.e. pattern matching against that tree to provide various capabilities like syntax highlighting, folding, indentation, smart textobject selection,...

For this, and until we can merge with nvim-treesitter itself, you will have to clone this github repository, then copy the queries/ directory to

  ~/.local/share/nvim/site/pack/packer/start/nvim-treesitter/queries/

Usage

Syntax highlighting

The above default configuration will replace the default regular expressions-based syntax highlighting in vim. Instead, the highlighting is based on the tree build every time you type something.

The default highlighting looks pretty much like the one from the standard Ada mode. However, the tree-based approach potentially opens the door for smart highlighting, like "Use a different background color for a subprogram specification", "show constant definitions in blue" or other high-level approaches.

WIP: document how users can do this in their own configuration files.
The current approach is to modify queries/highlights.scm

Potentially (though it seems to be disabled in neovim at the moment), the highlighting can also get smarter. Going back to the "show constants in blue" example above, the queries/locals.scm file adds a simple approach so that references to those constants can point to the definition, and therefore use the same blue highlighting.

Because neovim also has support for language servers (LSP), it is likely better to rely on the language server here.

Block folding

If you press za now, this will toggle the folding of the "current block". This is defined in queries/folds.scm, and currently knows about package specifications, package bodies, subprograms bodies, if statements and loops. Other semantic blocks could be added.

Smart Selection

The file queries/textobjects.scm defines a function textobjects, so that you can now use commands like

• vaf (v)isually select (a) (f)unction or subprogram
• vif (v)isually select (i)nside a (f)unction or subprogram
• vai (v)isually select (a) (i)f statement (or loop)
• vii (v)isually select (i)nside an (i)f statement (or loop)

Development

Execute the following commands:

   npm install
   npm run test

Documentation

The grammar itself is fully described in the file grammar.js. When it processes it, TreeSitter generates src/grammar.json, which can be converted to a EBNF format via https://github.com/mingodad/plgh/blob/main/json2ebnf.js and rendered into a diagram on https://www.bottlecaps.de/rr/ui if you prefer graphical visualization (you can also copy-paste from issue #1 a pre-processed version of grammar.json).