ADR-0046: Highlighters can register by file name

• Status: Accepted
• Date: 2026-08-10
• Deciders: jka
• Decision: D46

Context

The highlighter registry (ADR-0032) resolved a language by file extension only. Common build files have no extension (Makefile, Dockerfile), so they could not be highlighted.

Decision

register_filename <lang> {basenames} <scan> maps whole file names to a scanner, beside the extension map. Resolution order is:

1. exact file name;
2. extension;
3. file name with its last suffix removed (so Dockerfile.prod resolves).

An explicit extension always wins over the stripped-name guess, so Makefile.tcl is Tcl. Matching is case-insensitive, and a later registration still wins.

Consequences

• Makefile, Dockerfile, batch, PowerShell, awk and sed highlighters became useful.
• A language may register under both keys (Makefile by name and by .mk).
• Shebang detection (#!/usr/bin/awk) is not implemented and would be the next step.