#1149774 cl-abnf: `range-sep` Rule Referenced But Never Defined

Package:
cl-abnf
Source:
cl-abnf
Submitter:
Petter Reinholdtsen
Date:
2026-10-02 22:03:03 UTC
Severity:
normal
#1149774#5
Date:
2026-10-02 21:59:53 UTC
From:
To:
I tried using the cl-abnf to verify a ABNF grammar, but it proved to not
work. I got my artificial idiocy LLM to write up the details:

# cl-abnf Bug: `range-sep` Rule Referenced But Never Defined

## Summary

The `cl-abnf` library defines a `hex-range` rule that references
`range-sep`, but `range-sep` is never defined in the library. This
causes `parse-abnf-grammar` to fail with an undefined rule error when
parsing any ABNF grammar.

## Environment

- **Package**: cl-abnf
- **Version**: 20200229.gitba1fbb1-1 (Debian)
- **Upstream**: https://github.com/tapoueh/cl-abnf
- **Author**: Dimitri Fontaine <dim@tapoueh.org>

## Reproduction

Load cl-abnf and attempt to parse any ABNF grammar:

```lisp
(require 'asdf)
(asdf:load-system :abnf)
(use-package 'abnf)

;; This fails with an undefined rule error:
(parse-abnf-grammar "rule = \"test\"" "rule" :junk-allowed nil)
```

## Root Cause

In `abnf.lisp` line 318, the `hex-range` rule references `range-sep`:

```lisp
(defrule hex-range (and hexdigits range-sep hexdigits)
    ...)
```

However, `range-sep` is never defined anywhere in the library. The RFC
5234 ABNF specification defines `range-sep` as:

```abnf
range-sep = "-"
```

This rule is part of the core ABNF syntax rules that `cl-abnf` should
define internally for parsing ABNF grammars.

## Impact

Any attempt to parse an ABNF grammar with `parse-abnf-grammar` will
fail, as the library cannot resolve the `range-sep` reference. This
effectively renders the library unusable for its intended purpose of
parsing ABNF grammars.

## Workaround

Define the missing rule before parsing any grammar:

```lisp
(eval '(abnf:defrule range-sep "-" (:constant :range-sep)))
```

This must be evaluated in the `abnf` package before calling
`parse-abnf-grammar`.

## Expected Behavior

The library should define all core ABNF rules internally, including
`range-sep`, so that `parse-abnf-grammar` works out of the box without
requiring manual rule definitions.

## Suggested Fix

Add the missing rule definition to `abnf.lisp`:

```lisp
(defrule range-sep "-" (:constant :range-sep))
```

This should be placed alongside the other core rules in the library.

## References

- RFC 5234 Section 2.1:
https://datatracker.ietf.org/doc/html/rfc5234#section-2.1
- cl-abnf repository: https://github.com/tapoueh/cl-abnf