[Laszlo-dev] For Review: Change 20081121-dda-q Summary: Add ability to insert try/catch blocks around functions

[Donald Anderson]

Change 20081121-dda-q by dda at lester.local on 2008-11-21 10:21:40 EST
     in /Users/dda/laszlo/src/svn/openlaszlo/trunk-g
     for http://svn.openlaszlo.org/openlaszlo/trunk

Summary: Add ability to insert try/catch blocks around functions

New Features:

Bugs Fixed: LPP-7270 (swf9: debugger hanging)

Technical Reviewer: ptw (pending)
QA Reviewer: (pending)
Doc Reviewer: (pending)

Documentation:

Release Notes:

Details:
    This requested feature makes SWF9 similar like SWF8 and DHTML in  
the face of
    exceptions - in those systems, the exceptions are caught at the  
top level, and
    the program allowed to continue.  In our case, we catch the  
exceptions within
    every function body, report the error to the debug console, and  
return from the function.

.  To enable the feature, compile with -DcatchFunctionExceptions=true
    Some compilation problems were found in trying to use this feature  
with smokecheck.lzx
    for SWF9, so for the moment, this is not tied to the debug switch,  
but must be
    enabled explicitly.  This may be fixed soon.

    The basic premise is to change the ORIGINAL CONTENTS of a function  
to this:
        var $lzsc$ret:* = 0;
        try {
          $lzsc$ret = (function  () {
             with (this) {
                //ORIGINAL CONTENTS
          }}).call(this)
         }
         catch ($lzsc$e) {
            $lzsc$runtime.reportException("LPP-7270.lzx", 5, $lzsc$e)
         }
         finally {
            return $lzsc$ret
         }

    with the slight variation that if the original function is  
declared to return a type,
    then the closure is also typed e.g. function (): String { ...

    This construct has the property that it will compile almost any  
contents the same,
    preserving return values and reporting the same compiler errors,  
including paths
    that do not return a value.  For some reason, if the ORIGINAL  
CONTENTS contains a closure,
    the flex compiler will report errors that attributes and even  
globals
    cannot be seen within that closure.  So this transformation is not  
done when
    the function contains a closure.  Also, super() calls cannot be  
pushed into a closure, so the
    transformation is not done if a super call is contained.

    A toString() function was added to ASTFormalParameterList to show  
the return type of the function.

    catchFunctionExceptions=false is added to the build scripts for  
the LFC.  This is technically
    not needed at the moment, but when we attach the  
catchFunctionExceptions option to the debug
    option, it will be.

Tests:
    Regression (swf8,swf9,dhtml) x (smokecheck,lzpix,weather)

    This change tested using the following test program, compiling  
with both
    -DcatchFunctionExceptions=true and false, observing generated  
compiler output
    for both cases, and running it with both cases.  Only the  
catchFunctionExceptions=true
    allows the program to proceed after an exception.

    test program:
    <!-- ================================= -->
       <canvas debug="true">
         <simplelayout spacing="10" axis="y" />
            <class name="mywindow" width="300">
                <button onclick="this.parent.parent.canvas_f()"  
 >BaseClass mywindow</button>
            </class>

          <method name="canvas_f">
           Debug.info("1 zebra");
           Debug.info("2");
           t1.setText("Before exception");
           Debug.info("3...?");
           throwexcept(7,0);
           Debug.info("4!!");
           t2.setText("After exception");
          </method>
          <button name="b1" onclick="this.parent.canvas_f()"  
width="100" height="30" y="10">Press me</button>
          <text name="t1" bgcolor="#ccffcc" width="100" height="30"  
y="50"/>
          <text name="t2" bgcolor="#ccffcc" width="100" height="30"  
y="100"/>
          <mywindow bgcolor="#cc8c8c"/>
        <script>
        function throwexcept(w, x) {
          // divide by zero doesn't give an exception, but
          // an array reference of a non array will.
          return w[x]/x;
        }

        </script>
      </canvas>
    <!-- ================================= -->


Files:
M      WEB-INF/lps/lfc/buildlfc
M      WEB-INF/lps/lfc/buildlfcdebug
M      WEB-INF/lps/lfc/build.xml
M      WEB-INF/lps/lfc/compiler/LzRuntime.lzs
M      WEB-INF/lps/server/src/org/openlaszlo/sc/JavascriptGenerator.java
M      WEB-INF/lps/server/src/org/openlaszlo/sc/Compiler.java
M      WEB-INF/lps/server/sc/src/org/openlaszlo/sc/parser/ 
ASTFormalParameterList.java

Changeset: http://svn.openlaszlo.org/openlaszlo/patches/20081121-dda-q.tar



--

Don Anderson
Java/C/C++, Berkeley DB, systems consultant

voice: 617-547-7881
email: dda at ddanderson.com
www: http://www.ddanderson.com



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