Show a diff of single line JSON objects (IAM policy docs) in terraform

tf-plan-diff.sh

#!/bin/bash
#
# shellcheck disable=SC2001

set -e -o pipefail


input="$1"

[[ -n "$input" ]] || {
  [[ -t 0 ]] && { input="$(pbpaste)"; } || input="$(cat)"
}

# TODO: Deal with multiple lines in the input.

pattern='^(?: *[a-z0-9_]+: *)?(".*") => (".*")$'

before=$(echo "$input" | perl -p -e 'BEGIN { $/="" }; s/'"$pattern"'/$1/sm;' | jq -eS 'fromjson')
after=$(echo "$input" | perl -p -e 'BEGIN { $/="" }; s/'"$pattern"'/$2/sm;' | jq -eS 'fromjson')

diff -u <(echo "$before") <(echo "$after")