Parse Lua code and draw its call graph.

call_graph.awk

#!/usr/bin/awk -f
#
# call_graph.awk
#
# Usage:
#   ./call_graph.awk my_program.lua | dot -Tpng > call_graph.png
#
# This is a script that generates a visual call graph
# for a Lua file. This script only shows calls made
# to functions defined within the input Lua file; that is,
# it excludes calls such as standard library or built-in functions.
#
# Use the option "-v nodirect=1" to hide direct function calls;
# these are calls made from the top level of your Lua program.
# Example: ./call_graph.awk -v nodirect=1 my_program.lua
#

BEGIN {
  identifier = "[A-Za-z_][A-Za-z0-9_]*"
  fn_call = identifier "\\\("
  in_fn = "\"<direct call>\""
  if (!nodirect) defined_fns[in_fn] = 1

  print "strict digraph {"
  print "  node [shape=box color=\"#FFFFFF\" fontname=\"courier\" fontsize=12];"
  print "  edge [color=\"#CCCCCC\" arrowsize=0.8];"
}

# Detect and ignore comments.
/^--\[\[/ { in_a_comment = 1 }
/^--\]\]/ { in_a_comment = 0 }

# Detect when we are at the top-level of the program; out of any functions.
# This detection is not foolproof; it assumes the code is consistently indented.
/^ *end/ {
  indent = match($0, /[^ ]/) - 1
  if (indent == in_fn_indent) {
    in_fn = "\"<direct call>\""
  }
}

# Detect and track function definitions.
# This includes only functions declared at the start of a line.
/^ *(local *)?function/ {
  if (in_a_comment) next
  if ($1 == "local") { fn_name = $3 } else { fn_name = $2 }
  sub(/\(.*/, "", fn_name)
  defined_fns[fn_name] = 1
  in_fn = fn_name
  in_fn_indent = match($0, /[^ ]/) - 1
  next  # Don't consider this line as a function call.
}

# Track function calls.
$0 ~ fn_call {
  if (in_a_comment) next
  fn_index = match($0, fn_call)
  comment_index = match($0, /--/)
  if (comment_index && comment_index < fn_index) next
  tail = substr($0, match($0, fn_call))
  fn_name = substr(tail, 1, index(tail, "\(") - 1)
  calls[in_fn " -> " fn_name] = 1
  # Uncomment the following line to help debug this script.
  #printf "%d: called_fns[%s] = %s\n", NR, fn_name, in_fn
}

END {
  for (call in calls) {
    split(call, fns, " -> ")
    if (defined_fns[fns[1]] && defined_fns[fns[2]]) {
      print "  " call
    }
  }

  print "}"
}

Cross-reference: https://gist.github.com/outsinre/1ca61b5c5d7b49b528f5b480a1dff96e