My current autoacme event handler script

acme-autoformat

#!/usr/local/plan9/bin/rc

. 9.rc
. $PLAN9/lib/acme.rc

event=$1
target=$2

fn hashbang {
	awk '
		function basename(path) {
			sub(".*/", "", path)
			return path
		}
		NR == 1 && /^#!/ {
			$0 = substr($0, 3)
			cmd = basename($1)
			if(cmd == "env")
				cmd = basename($2)
			print cmd
		}
	' $target
}

fn fmt-python {
	black --line-length 79 --quiet -
}

switch($event$target) {
case put*.elm
	elm-format --stdin <$target | acmepipe
case put*.ex put*.exs
	mix format - <$target | acmepipe
case put*.go
	goimports $target | acmepipe
	# Linters:
	# go vet
	# golint
	# errcheck
	# megacheck
	# Formatters:
	# goimports
	# goreturns
	# gofmt
case put*.py
	fmt-python <$target | acmepipe
case put*.rb
	rubocop --format emacs $target
case put*.rs
	rustfmt --write-mode plain $target | acmepipe
case put*.js
	npx eslint --format unix $target
case put*yaml put*yml
	yamllint --format parsable $target
case put*
	switch(`{hashbang}) {
	case sh
		shfmt -ln posix $target | acmepipe
	case bash
		shfmt -ln bash $target | acmepipe
	case mksh
		shfmt -ln mksh $target | acmepipe
	case python*
		fmt-python <$target | acmepipe
	case ruby*
		rubocop --format emacs $target
	}
}