Formatter

The formatter changes only whitespace and line breaks in a reader spec. Tokens, comments, strings, names, numbers, and statement order stay as they are, and text inside a line pattern is kept byte for byte, including captures and spaces.

Before and after

This pair comes from the repository’s formatting guide. The site checks the result against the formatter when it is built.

Before

# dimensions
n:int    # number of rows


repeat n { # records
 # keep this comment before the field
 x: # field type
 int
}

After

# dimensions
n: int # number of rows

repeat n { # records
  # keep this comment before the field
  x: # field type
    int
}

The style

• Put each statement on its own line and indent brace bodies by two spaces.
• Expand nonempty blocks; write empty blocks as {}. Keep } else together unless a comment or blank line separates it.
• Use name: type, tight array brackets and ranges, spaces around binary operators, and a space after commas. Do not align columns.
• Keep comments attached to the same tokens. Do not reword, wrap or move them to another line.
• Keep interior single blank lines, collapse longer runs, and trim blank lines at file edges and directly inside braces.
• Use LF outside protected string and comment text, with one final LF in a nonempty file. Empty files stay empty.

When a line needs wrapping, move a check’s message first, then option groups and string lists, before breaking expressions. Expression breaks follow the loosest operator precedence and keep operators on the preceding line. Calls put one argument per line when broken. Continuations add two spaces, without column alignment. Indivisible tokens and comments may exceed the target width. The full guide defines the remaining details and exceptions.

Line width

The only setting is max_line_length in .editorconfig, looked up for the reader spec’s path. The default is 100 when the property is absent, unset, or off. Other properties do not affect formatting: indentation remains two spaces. Widths count Unicode scalar values, rather than bytes or terminal display cells.

The language server uses the same formatter and lookup for file URIs. Untitled documents use width 100. Formatter output changes only in minor package releases, with style changes recorded in the Rust changelog.

Use the formatter

Build the CLI and use its in-place, check, and diff modes. For standard input, run this from the repository root with iris on PATH. Pipe the unformatted reader spec into it, or paste it and close standard input:

iris fmt -

The command prints formatted source and uses width 100. Add --stdin-filepath with a reader-spec path to use its EditorConfig hierarchy; that path need not exist and is never written. - must be the only operand.

Whole-document formatting refuses syntax errors. Range formatting in the language server can format a clean statement sequence when other parts have syntax errors. Neither mode requires successful semantic analysis. See source syntax and syntax errors in the Specification.