Truthiness in Terraform 0.11 and 0.12

#!/usr/bin/env bash

# Code for my blog post at:
# https://alexharv074.github.io/2019/06/09/adventures-in-the-terraform-dsl-part-v-conditional-logic.html

t011=/usr/local/bin/terraform
t012=/usr/local/bin/terraform012

data() {
cat <<EOF
  "1"
  "0"
  true
  false
  "true"
  "false"
  1
  0
  "2"
  "hello"
  ""
  true == true
  false == false
  true == "true"
  false == "false"
  true != "true"
  false != "false"
  "1" == true
  "0" == false
  "1" == "true"
  "0" == false
  "x" == "x"
  "x" == "y"
  !true
  !false
  !!true
  !!false
EOF
}

filter() {
  awk '
    # Written this way to deal with unprintable
    # characters in the input.
    #
    /truthiness/ { ++f }
    /truthiness.*truthy/ { print "truthy" }
    /truthiness.*falsey/ { print "falsey" ; next }
    /truthiness.*true/ { print "true" }
    /truthiness.*false/ { print "false" }
    /invalid syntax in/  { ++f; print "-" }
    /must be type bool/  { ++f; print "-" }
    /must be of type bool/ { ++f; print "-" } # Message changed in 0.12.
    END {
      if (!f) print "-"
    }
  '
}

echo "|Value|Terraform 0.11|Terraform 0.12|
|=====|=============|==============|"

data | while read i ; do

  t='truthy' ; f='falsey'
  if [[ $i =~ = ]] || [[ $i =~ ! ]] ; then
    t='true' ; f='false'
  fi

  cat > "test.tf" <<EOF
output "truthiness" {
  value = "\${$i ? "$t" : "$f"}"
}
EOF

  row="|$i"
  for j in 11 12 ; do
    rm -f terraform.tfstate*
    ter="\$t0$j"
    val=$(eval "echo \$($ter apply 2>&1 | filter)")
    row="$row|$val"
  done
  row="$row|"
  echo "$row"
done