node.js line number debug utility script - returns call site info for debugging purposes - compatible with TypeScript & ES5+

debug-util.js

/*
 * Copyright (c) 2016 Nicholas Folse -- All Rights Reserved
 * 
 * debug-util.js -- Call site info for debugging javascript 
 * 
 * requires node 'source-map' (npm install source-map)
 *
 * usage:
 *
 * const debug_line = require("../debug-util");
 *
 * function myFunc() {
 *   console.log(debug_line());
 * }
 *
 */
"use strict";

var sourceMap = require("source-map");
var fs = require("fs");
var path = require("path");

function prepareStackTrace(_, stack) {
  return stack;
}

var __sourceMapCache = {};

function getSourceMap(fileName) {
  var srcmap = __sourceMapCache[fileName];
  if (srcmap) {
    return srcmap;
  }
  try {
    var smc = new sourceMap.SourceMapConsumer(JSON.parse(fs.readFileSync(fileName, "utf-8")));
    if (smc) {
      __sourceMapCache[fileName] = smc;
      return smc;
    }
  } catch (e) {
  }
}

function debug_line(stackOffset) {
  var offset = stackOffset || 0;
  var orig = Error.prepareStackTrace;
  Error.prepareStackTrace = prepareStackTrace;
  var err = new Error();
  var stack = err.stack;
  Error.prepareStackTrace = orig;

  var cs = stack[1 + offset];

  var file = cs.getFileName();
  var line = cs.getLineNumber();
  var column = cs.getColumnNumber();
  var functionName = cs.getFunctionName() || "<anonymous>";
  var summary = path.basename(file) + ":" + line + ":" + column + "(@" + functionName + ")";

  var src = file, lineNo = line, colNo = column;
  var map_file_src = src + '.map';

  var lineDef = {source: file, line: lineNo, column: colNo, summary: summary};
  var srcMap = getSourceMap(map_file_src);
  var origSrc = srcMap.originalPositionFor({line: lineNo, column: colNo});
  lineDef.source = origSrc.source;
  lineDef.line = origSrc.line;
  lineDef.column = origSrc.column;
  lineDef.summary = path.basename(origSrc.source) + ":" + origSrc.line + ":" + origSrc.column + "(@" + functionName + ")";
  return lineDef;
}

module.exports = debug_line;