Skip to content
Preprocessor for Actionscript 3 code which wraps every function in try/catch blocks providing stacktrace tracking without debug flash player
Scala ActionScript
Find file
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.
.gitignore Static/function methods and bugfixes. Feb 20, 2012

Actionscript 3 Stacktracer

This tool preprocesses AS3 code and wraps every method in try/catch statements. This provides at least rudimentary stacktrace support on non-debug flash players.


Get SBT from, enter this directory and launch sbt assembly. Having JDK is required. Result will be in target/as3_st.jar.


To precompile one directory and output source to another:

java -jar as3_st.jar src_dir dst_dir

Unsupported files will be skipped.

To transform files in place:

java -jar as3_st.jar

This tool supports .as and .mxml files.

When running, it outputs one character for each file:

  • p - file has been preprocessed.
  • . - no update needed.
  • c - file type not supported, file is copied instead.
  • s - file preprocessing was skipped, file is copied instead.

To compile your precompiled source you will need to include files from as3 directory into your project. You may modify them to suit your project needs.


Configuration is placed in as3stacktracer.conf file in working directory.

Example configuration:

force = false
verbose = false
skipped = [
  • force - precompile files even if we can't detect any change in them.
  • verbose - show full messages instead of symbols.
  • skipped - array of regexps which files should not be preprocessed. Windows dir separators are converted to unix, so always use / here. Java regexp modifier flags (i.e. "(?i)foo") can be used here.

Features missing / not supported

  • All statements must be terminated with semicolon

    // not supported: must have ; at the end of statement
  • Line numbers are supported but only inside functions for now and they are not always exact.

  • Cannot have string literals as default values for function arguments

    // Unsupported. Extract to a constant
    function foo(name: String = "Unknown"): void {}
    // OK
    private static const DEFAULT_NAME = "Unknown";
    function foo(name: String = DEFAULT_NAME): void {}
  • Cannot have comments

    • between package/class/function declaration and body.

      package foo
      // This is not supported
    • between if and (...), else and if, else and it's body

      if /* not supported */ (...) {}
      else /* not supported */ if (...) {}
      else // not supported
      // Legal comment
      if (...) {}
      // Legal comment
      else if (...) {}
      // Legal comment
    • between for and each, loop keyword and (...)

      for /* not supported */ each /* not supported */ (...) {}
      while /* not supported */ (...) {}
  • Variables declared without var are not tracked.

    var a: String, b: String; // b will not be tracked.
  • Regular expressions that have quotes (single or double) in their body will cause errors after preprocessing.

    // Not OK. Use:
    // new RegExp("abc['\"]", "g")
    var r: RegExp = /abc['"]/g;
    // OK. No quotes in the body.
    var r: RegExp = /abc/g
  • Braces are still optional after control flow statements if their body contains only one statement, but there is one caveat: you must use braces if control flow body contains if else block

    // Not OK. Preprocessor will enclose the inner if statement inside braces
    // but will leave out the else part.
    for (i: int = 0; i < 10; i++)
        if (i < 5) foo();
        else bar();
    // This is OK.
    for (i: int = 0; i < 10; i++) {
        if (i < 5) foo();
        else bar();
  • Multiple nested try/catch blocks are not supported.

    // This is not supported.
    function func1() {
      try { foo(); }
      catch (err1: Error) {
        try { foo2(); }
        catch (err2: Error) {
    // Recommended workaround is:
    function func1() {
      try { foo(); }
      catch (err1: Error) { func2(); }
    function func2() {
      try { foo2(); }
      catch (err2: Error) {


Artūras Šlajus (


This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

Something went wrong with that request. Please try again.