Bash script to find unused custom template tags and filters

find_dead_template_tags.sh

#!/usr/bin/env bash
# 
# Helper script to look for unused template tags and filters.
#
# Run this in the root of your project and it will print out template tags and filters that 
# aren't used anywhere.
#
# Requires ripgrep (rg).

set -e

function main() {
    echo "Looking for unused template tags"
    look_for_dead_tags

    echo "Looking for unused template filters"
    look_for_dead_filters
}

function look_for_dead_tags() {
    local tag
    local freq
    # Stream input via non-standard file descriptor to avoid stdin-consumption issue from rg.
    while read -u9 tag; do
        if ! is_tag_used "$tag"
        then
            echo $tag
        fi
    done 9< <(tag_names)
}

function look_for_dead_filters() {
    local filter
    local freq
    # Stream input via non-standard file descriptor to avoid stdin-consumption issue from rg.
    while read -u9 filter; do
        if ! is_filter_used "$filter"
        then
            echo $filter
        fi
    done 9< <(filter_names)
}

# Print a stream of template tag names.
function tag_names() {
    rg --no-filename "@register.(simple_)tag" -A1 | \
        grep "^def " | \
        cut -d" " -f2 | cut -d"(" -f1 
}

# Print a stream of template filter names.
function filter_names() {
    rg --no-filename "@register.filter" -A1 | \
        grep "^def " | \
        cut -d" " -f2 | cut -d"(" -f1 
}

# Test if a passed template tag is in use.
function is_tag_used() {
    local tag=$1
    [ $(tag_frequency "$tag") -gt 0 ]
}

# Test if a passed template filter is in use.
function is_filter_used() {
    local filter=$1
    [ $(filter_frequency "$filter") -gt 0 ]
}

# Print the frequency that the passed template tag is used to stdout.
function tag_frequency() {
    local tag=$1
    rg -F "{% $tag " | wc -l
}

# Print the frequency that the passed template filter is used to stdout.
function filter_frequency() {
    local filter=$1
    rg "\|\s*$filter" | wc -l
}

main

I updated the tag regex to add support for inclusion_tag, meaning the regex on mine is rg --no-filename "@register.(simple_|inclusion_)tag" -A1

Thanks for this 👍

Thanks @benhowes - good tip