Customizing Injections

This is an example of how to setup pruner to format SQL embedded inside of Rust. Take the following Rust snippet with a SQL query as a reference:

async fn get_users(pool: &PgPool) -> Result<Vec<User>> {
  let query = "SELECT
                 id,
                 name,
                 email
               FROM
                 users
               WHERE
                 active = TRUE
               ORDER BY
                 created_at DESC";
  let users = sqlx::query_as::<_, User>(query).fetch_all(pool).await?;
  Ok(users)
}

By default the query string is treated as an opaque string and Pruner has no idea that it contains SQL and should be formatted as such.

We can change this by defining a simple treesitter language injection query:

;; queries/rust/injections.scm
((string_content) @injection.content
  ;; Regex match for a string containing text that looks like a SQL query
  (#match? @injection.content "^(SET|TRUNCATE|SELECT|CREATE|DELETE|ALTER|UPDATE|DROP|INSERT|WITH)")
  ;; Inform Pruner that any '"' characters should be escaped.
  (#escape! @injection.content "\"")
  ;; Label this region as SQL
  (#set! injection.language "sql"))

Next Pruner will need to be configured appropriately:

• We need to add the queries directory to Pruners' query search paths
• We need to configure pruner to format Rust and SQL
• We need to add the Rust treesitter grammar to allow parsing the rust code

query_paths = ["queries"]

[grammars]
rust = "https://github.com/tree-sitter/tree-sitter-rust"

[formatters]
rustfmt = { cmd = "rustfmt", args = ["--emit=stdout", "--edition=2024"] }

pg_format = { cmd = "pg_format", args = [
  "--spaces=2",
  "--wrap-limit=$textwidth",
  "-",
] }

[languages]
sql = ["pg_format"]
rust = ["rustfmt"]

And that should be sufficient. Now you can run pruner format --lang rust against the above source code and the embedded SQL will be formatted as well.

Editor Integration

If you want the above Rust snippet to also be highlighted like SQL in your editor, and you are using Neovim (or an editor which uses treesitter under the hood), then you can!

For example, if you are on Neovim, you can take the same injection query defined above and place it at ~/.config/nvim/queries/rust/injections.scm and you will get SQL highlighting for the same snippet!

You can read more about this in this article.