file_is_ascii

Every byte in the file must be < 0x80 (pure ASCII), except codepoints listed in allow:. Strict variant of is_text for configs that must round-trip through strictly-ASCII tools. allow: exempts specific non-ASCII codepoints — each entry a single character ("ö"), a U+XXXX codepoint, or a U+XXXX-U+YYYY inclusive range (curl keeps its source ASCII but allows ö in “Björn”; the recurring need across llvm / vscode / elixir). With allow: the file is decoded as UTF-8 and checked per character; without it, the strict byte-level fast path is used.

---

Options

Option	Type	Required	Default	Description
allow	list of string		[]	Permitted non-ASCII codepoints - each a single character (e.g. “o-umlaut”), a U+XXXX codepoint, or a U+XXXX-U+YYYY inclusive range.

Plus the common paths, level, id, and when fields. This table is generated from the JSON Schema; option types and defaults are authoritative.

Example

A source file with a non-ASCII byte

The rule fires on this repository:

src/
src/ascii.rs
src/unicode.rs

src/ascii.rs

pub fn ok() {}

src/unicode.rs

// The ☃ is here
pub fn cold() {}

With this .alint.yml:

version: 1
rules:
  - id: ascii-only
    kind: file_is_ascii
    paths: "src/**/*.rs"
    level: error

alint check reports:

--- src/unicode.rs -------------------------------------------------------------
  x  error    ascii-only
              non-ASCII byte 0xE2 at offset 7

Summary (1 violation):
  x 1 error
  0 passing * 1 failing

Every source file is pure ASCII

This repository is compliant:

src/
src/a.rs
src/b.rs

src/a.rs

pub fn a() {}

src/b.rs

pub fn b() { let _ = 42; }

With this .alint.yml:

version: 1
rules:
  - id: ascii-only
    kind: file_is_ascii
    paths: "src/**/*.rs"
    level: error

alint check reports:

v All 1 rule(s) passed.