Formatting on save

Configure your editor to send the current buffer to zincite fmt and replace it with the formatted output only when the command succeeds. This also works for files that have not been saved yet.

After installing Zincite, use the installed executable and these arguments in your editor’s external-formatter settings:

fmt --stdin-filepath /absolute/path/to/the/edited/model.mzn

The command name is zincite. If your editor needs an absolute executable path, use the path reported by command -v zincite. If you installed the standalone zincite-fmt instead, use that executable and omit fmt.

Send the current in-memory buffer as UTF-8 on stdin. Use the actual destination path, even for a new file that has not been saved yet. A .dzn path selects data syntax; other paths select model syntax. The path also selects the EditorConfig lookup starting directory and appears in diagnostics. No input argument is needed: the command reads stdin by default. Plain stdin without --stdin-filepath uses model syntax and default settings without filesystem configuration lookup.

The default style uses four spaces, LF, a final newline and a 120-column limit. EditorConfig supplies indentation, tab width, editable line endings, width, final-newline and trailing-whitespace settings, and UTF-8/BOM selection. Supported command-line style overrides take precedence; see --help for their values and the formatting style gallery for examples. Formatting may change between versions in the 0.x series.

Editor recipe

1. Take the edited buffer and its destination path at the start of the save.
2. Start one fresh formatter process, passing the path as one argument. Send the complete buffer on stdin and capture stdout and stderr separately.
3. Wait for process completion and complete stdout capture. On exit status 0, replace the buffer with the captured stdout, then save it. An already formatted buffer produces the same bytes. Successful output may be empty for empty input.
4. On nonzero status, timeout, launch failure or incomplete output capture, keep the original buffer and show stderr or the process failure through the editor’s usual diagnostic UI. Follow the editor’s existing policy for saving that unchanged buffer.

Do not stream stdout into the buffer, merge stderr into source, or treat a nonempty stdout fragment as success. Syntax, formatting-directive, configuration, usage and I/O errors exit 2. Syntax, directive and configuration failures produce no formatted stdout. Status 1 belongs to --check, so use the default stdout mode for this recipe. --write writes disk files and does not format an unsaved buffer.

For an editor adapter written in Python, the buffer replacement can look like this. The helper functions belong to the editor integration:

import subprocess

# buffer_bytes and destination_path come from the editor.
original = buffer_bytes
try:
    result = subprocess.run(
        [zincite_path, "fmt", "--stdin-filepath", destination_path],
        input=original, capture_output=True, timeout=30, check=False,
    )
except (OSError, subprocess.TimeoutExpired) as error:
    show_process_error(error)             # keep original
else:
    if result.returncode == 0:
        replace_buffer(result.stdout)    # complete output, including empty output
    else:
        show_diagnostics(result.stderr)  # keep original

zincite_path is the installed executable. Launching cargo run on every save would also invoke Cargo. Formatting a buffer does not load includes or run lint checks; configure linting as a separate editor action if you want that feedback.

Performance

Use a release build for editing. The project targets saves below 100 ms at the 95th percentile for its ordinary editing cases; large generated data can take longer. The performance reports contain the measured inputs, timings and methodology.