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From Greg Roodt <gro...@gmail.com>
Subject Re: Rhino global.load() in script context
Date Sun, 22 Aug 2010 08:12:29 GMT
Hi

Glad it worked.

I agree with you. I think it would be much easier and more useful if these
functions from the Rhino shell were made available. It is not something that
the <script /> task is going out of its way to remove though, the problem is
actually Rhino/javascript itself (not a problem, more a strictness). The
javascript language spec does not specify these functions, therefore they
are not made available in the interpreter and JSR 223.

All that the <script /> task essentially does is the following:
1. Determine which script engine to use.
2. Fire up the script engine.
3. Inject Ant objects (project, tasks etc.) into the Context of the script.
This is to help make it possible to use scripting languages to write Ant
scripts, remember this task is not meant to be a general purpose script
runner, but a way to make it simpler to script Ant tasks.

The Rhino Shell then confuses people, by providing all these wonderful
functions that arent available in a standard embedded context which is a bit
frustrating. Other languages like python do indeed have much more useful
things baked directly into the language which makes them easier to use.

I think you should bring this up on the dev list and see what they think. It
might be that the Global stuff can be made available which will then make
javascript and the <script /> tag much more powerful. Or they might suggest
creating a new Ant task <rhinoshell /> or something.

Cheers
Greg








On Sat, Aug 21, 2010 at 11:44 PM, Jacob Beard <jbeard4@cs.mcgill.ca> wrote:

> Hi Greg,
>
> Thanks a lot for this! This does exactly what I want.
>
> I had actually just about given up, as I realized that the load function I
> was attempting to define would have the shortcoming of essentially capturing
> any local variables eval'ed within it. This mean that while dojo worked
> because it was declared in the global scope, RequireJS would not load
> because its top-level argument ("require") was declared using var.
>
> I'm mentioning this now only because it's amusing, but to work around this,
> I tried imagining a way to exit the load function to eval the string to be
> loaded, thus allowing local variables declared within the string to be
> declared in the global scope; then returning from the global scope to the
> call site of the load function. The only way I could think to do this was
> with continuations. Converting to the continuation-passing style was not an
> option, because passing in a callback to load would break the API.
> Fortunately, Rhino exposes a native Continuation. After some playing around,
> I found that this code had the desired effect:
>
> /*
>
>    this file is to test a technique for creating a load function in Rhino
>
> */
>
> (function(){
>
>    myLoadLocal = function(str){
>
>        eval(str);
>
>    }
>
>    function call_with_current_continuation() {
>
>        var kont = new Continuation();
>
>        return kont;
>
>    }
>
>    var evalString = null, afterEval = null;
>
>    var beforeEval = call_with_current_continuation();
>
>    if(evalString){
>
>        eval(evalString);
>
>        evalString=null;
>
>        afterEval(null);
>
>    }
>
>    myLoadContinuation = function(str){
>
>        evalString = str;
>
>        afterEval = call_with_current_continuation();
>
>        if(afterEval instanceof Continuation){
>
>            beforeEval(beforeEval);
>
>        }else{
>
>            return;
>
>        }
>
>    }
>
>    myLoadLocal("var foo=1;");
>
>    print(typeof foo);    //should be undefined
>
>    myLoadContinuation("var bar=2;");
>
>    print(typeof bar);    //should be number
>
>    print(bar);        //should be 2
>
>    //see if it works again
>
>    myLoadContinuation("var bat=3;");
>
>    print(typeof bat);    //should be number
>
>    print(bat);        //should be 3
>
> })()
>
>
> I think there's probably a more elegant way to use continuations to do
> this, but this was the first thing I got working. One caveat to this,
> however, is that Continuations in Rhino only work when run in interpreted
> mode, without optimizations (-opt -1). Otherwise it fails with the following
> error:
>
> js: Direct call is not supported
>
> When I brought this back into the Ant script context, it failed with this
> error as well, so it appears that this technique would not work in Ant for
> this reason.
>
>
> I wonder if its worth discussing whether removing the global functions
> normally found in Rhino is a desirable behaviour for Ant. Other scripting
> languages include facilities for importing code as part of their core syntax
> (e.g. Jython's import statement), so this cannot be easily removed for them,
> but for Rhino, the load function is simply part of the global object, and
> can be easily removed from the embedding context. But I'm not sure if this
> is actually a good thing to do. Certainly it reduces the utility of the Ant
> script context, and increases its verbosity for situations where external
> scripts must be loaded via a module loader, such as Dojo or RequireJS. Do
> you think this is something that would be worth bringing up on the
> developer's list? Would it be useful to file a bug report or feature
> request?
>
> Let me know what you think. Thanks,
>
> Jake
>
>
>
> On 10-08-21 05:37 PM, Greg Roodt wrote:
>
>> This might work for you:
>>
>>     <project default="hello" name="helloworld" basedir=".">
>>        <target name="hello">
>>            <script language="javascript" manager="bsf">
>>            <classpath>
>>                <fileset dir="rhino-lib" includes="*.jar"></fileset>
>>            </classpath><![CDATA[
>>            importPackage(java.lang, java.util, java.io);
>>            System.out.println("Hello from JavaScript!!");
>>            //create shell, execute something and grab global
>>            var shell = org.mozilla.javascript.tools.shell.Main;
>>            var args = ["-e","var a='STRING';"];
>>             shell.exec(args);
>>            var shellGlobal = shell.global;
>>
>>            //grab functions from shell global and place in current global
>>            var load=shellGlobal.load;
>>            var print=shellGlobal.print;
>>            var defineClass=shellGlobal.defineClass;
>>            var deserialize=shellGlobal.deserialize;
>>            var doctest=shellGlobal.doctest;
>>            var gc=shellGlobal.gc;
>>            var help=shellGlobal.help;
>>            var loadClass=shellGlobal.loadClass;
>>            var quit=shellGlobal.quit;
>>            var readFile=shellGlobal.readFile;
>>            var readUrl=shellGlobal.readUrl;
>>            var runCommand=shellGlobal.runCommand;
>>            var seal=shellGlobal.seal;
>>            var serialize=shellGlobal.serialize;
>>            var spawn=shellGlobal.spawn;
>>            var sync=shellGlobal.sync;
>>            var toint32=shellGlobal.toint32;
>>            var version=shellGlobal.version;
>>            var environment=shellGlobal.environment;
>>
>>            //test your bad self
>>            load("test.js");
>>
>>            ]]></script>
>>        </target>
>>     </project>
>>
>> test.js:
>> var a = function() {
>> print("test");
>> help();
>> var scriptContents = readFile("test.js");
>> print(scriptContents);
>> var ver = version();
>> print("version:"+ver);
>> print(this);
>> for(var prop in this){
>> print(prop);
>> }
>> }
>> a();
>>
>>
>>
>> On Sat, Aug 21, 2010 at 7:03 PM, Jacob Beard<jbeard4@cs.mcgill.ca>
>>  wrote:
>>
>>
>>
>>> Hi Greg,
>>>
>>> Thanks for your response. Replies below:
>>>
>>>
>>> On 10-08-21 01:41 PM, Greg Roodt wrote:
>>>
>>>
>>>
>>>> I believe load() is part of Rhino Shell. I think all that the<script />
>>>> task runs when using JavaScript is the interpreter. It would only have
>>>> the
>>>> pure Javascript standard language features (and a few bits and pieces to
>>>> interact with Java and the execution context).
>>>>
>>>>
>>>>
>>>>
>>> load() is normally exposed as part of the global object when running
>>> Rhino,
>>> in the shell or the interpreter. All the js module loaders that support
>>> Rhino that I've encountered, including RequireJS and dojo, make use of
>>> load() to load JavaScript modules.
>>>
>>>  It might be easier to run the shell for each test? Like so:
>>>
>>>
>>>> java org.mozilla.javascript.tools.shell.Main [options]
>>>> script-filename-or-url [script-arguments]
>>>> https://developer.mozilla.org/en/Rhino_Shell#Invoking_the_Shell
>>>>
>>>> Or like John Resig does with env.js:
>>>> http://ejohn.org/blog/bringing-the-browser-to-the-server/
>>>>
>>>>
>>>>
>>>>
>>> I'm using that technique for other parts of my code, but it would be much
>>> easier to simply hook into Ant's ResourceSet data structures for this
>>> part,
>>> as it's possible to register a number of unit tests with dojo before
>>> running
>>> them.
>>>
>>>
>>>  Or maybe, define your own global load() function inside the<script />
>>>
>>>
>>>>  tag?
>>>>
>>>>
>>>>
>>>>
>>> That's what I'm working on. This seems to work, but I still need to test
>>> it
>>> with the dojo module loader:
>>>
>>>        <script language="javascript" manager="bsf">
>>>
>>>            <classpath>
>>>
>>>                <fileset dir="../../../lib/java/" includes="js.jar"/>
>>>
>>>                <fileset dir="../../../lib/build-java/"
>>> includes="*.jar"></fileset>
>>>
>>>            </classpath><![CDATA[
>>>
>>>            //define load in global scope
>>>
>>>            function readFile(path){
>>>
>>>                stream = new java.io.FileInputStream(new
>>> java.io.File(path));
>>>
>>>                fc = stream.getChannel();
>>>
>>>                bb =
>>> fc.map(java.nio.channels.FileChannel.MapMode.READ_ONLY,
>>> 0, fc.size());
>>>
>>>                return
>>> java.nio.charset.Charset.defaultCharset().decode(bb).toString();
>>>
>>>            }
>>>
>>>            load = function(path){
>>>
>>>                eval(String(readFile(path)))
>>>
>>>            }
>>>
>>>            echo = helloworld.createTask("echo");
>>>
>>>            var contents = readFile('hello.js')
>>>
>>>            echo.setMessage(contents);
>>>
>>>            echo.perform();
>>>
>>>            load('hello.js')
>>>
>>>            echo.perform();
>>>
>>>        ]]></script>
>>>
>>> hello.js:
>>>
>>> echo.setMessage("hello world!");
>>>
>>>
>>> Outputs:
>>>
>>> hello:
>>>
>>>     [echo] echo.setMessage("hello world!");
>>>
>>>     [echo] hello world!
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Jake
>>>
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>>>
>>>
>>>
>>>
>>
>>
>
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