#!/usr/bin/env bash
#
# Forbid scripts containing a dot in their filename.
# The aim is to forbid encoding the implementation language.
#
# This is a very common antipattern.  Almost, dominant.  But it's bad.
# It means call sites (including maybe out-of-tree) and human habits
# must change if the script is rewritten in a different language.
#
# This rule only applies to *executable* files, which can be invoked
# by their name.  Script modules or fragments which are to be included
# are fine, since their language is part of their API.

set -euo pipefail

fail () {
    echo >&2 "error; $*"
    exit 8
}

if [ "$#" != 0 ]; then
    fail "no arguments allowed"
fi

wrong=$(
    # shellcheck disable=SC2086
    find -H . -xdev \( -name .git -prune \) -o \( \
	 -type f -name '*.*' \! -name '*~' -perm /111 \
	 -ls \
    \)
)

if [ "$wrong" = "" ]; then exit 0; fi

printf '%s\n' "$wrong"

fail 'dot is forbidden in script filenames
(scripts should not encode their implementation language in their filename)'