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From Keith Suderman <suder...@anc.org>
Subject Re: Remembering imports between script invocations
Date Sat, 10 Feb 2018 20:25:23 GMT
Import statements are really just shortcuts to tell the compiler how to resolve class names
so there is nothing to "remember" between invocations, that is, nothing gets added to the
Binding.

I am not familiar with the javax.script API, but I suspect that you will have to provide your
own ScriptEngine implementation as you will need to modify the CompilerConfiguration object
the GroovyShell is using to compile the Groovy code.  For example:

        CompilerConfiguration configuration = new CompilerConfiguration()
        GroovyShell compiler = new GroovyShell(configuration)
        println compiler.evaluate('json=\'{"foo":"bar"}\'')
        println compiler.evaluate("groovy.json.JsonOutput.prettyPrint(json)")

        /* Fails: MissingPropertyException */
        /* println compiler.evaluate("JsonOutput.prettyPrint(json)") */

        ImportCustomizer imports = new ImportCustomizer()
        imports.addStarImports("groovy.json")
        configuration.addCompilationCustomizers(imports)
	// Works, the compiler can now resolve groovy.json.JsonOutput
        println compiler.evaluate("JsonOutput.prettyPrint(json)")

The difficult part will be "hooking" into the compiler to know when an import statement is
used so you can update your CompilerConfiguration object.  I am sure the really clever programmers
here could come up with some sort of AST transform that would do this.  However, depending
on what you are allowed to do one option would be to tell your users that you have a "Groovy
DSL" and then implement an "include" method that users would use to "import" Java packages.

        println eval('json=\'{"foo":"bar"}\'')
        println eval('include "groovy.json"')
        println eval('JsonOutput.prettyPrint(json)')
	
    Object eval(String code) {
        Script script = compiler.parse(code)
        ExpandoMetaClass metaClass = new ExpandoMetaClass(script.class, false)
        metaClass.include = { String name ->
            ImportCustomizer includes = new ImportCustomizer()
            includes.addStarImports(name)
            configuration.addCompilationCustomizers(includes)
            "Imported $name"
        }
        metaClass.initialize()
        script.metaClass = metaClass
        script.run()
    }

Hopefully that gives you some ideas.

Cheers,
Keith

> On Feb 8, 2018, at 3:47 PM, David Ekholm <david@jalbum.net> wrote:
> 
> How do I do that via the javax.script API?
> 
> Even if this is possible via the javax.script API, chances are that a user wishes to
ad-hoc add another import, but as they are forgotten between script invocations, it makes
it hard to use Groovy to interactively create, say a Swing or JavaFX UI one line at a time.
With BeanShell, the user can add the needed imports, execute that "script" and then continue
to refer to the imported classes in the following script invocations. Making Groovy remember
imports would make it behave in as nice fashion as the new JShell tool in Java 9. JShell unfortunately
cannot run embedded via the javax.script API :-(
> 
> Regards
> /David
> 
>> On 8 Feb 2018, at 21:34, eric.milles@thomsonreuters.com <mailto:eric.milles@thomsonreuters.com>
wrote:
>> 
>> You can add all the imports you want to your compiler configuration and they will
be consistently available for all scripts.
>>  
>> From: David Ekholm [mailto:david@jalbum.net <mailto:david@jalbum.net>] 
>> Sent: Thursday, February 08, 2018 2:12 PM
>> To: dev@groovy.apache.org <mailto:dev@groovy.apache.org>
>> Subject: Remembering imports between script invocations 
>>  
>> We're considering supporting Groovy as an additional scripting language to our web
gallery software jAlbum (http://jalbum.net <https://urldefense.proofpoint.com/v2/url?u=http-3A__jalbum.net&d=DwMFAg&c=4ZIZThykDLcoWk-GVjSLmy8-1Cr1I4FWIvbLFebwKgY&r=tPJuIuL_GkTEazjQW7vvl7mNWVGXn3yJD5LGBHYYHww&m=39n_uU4e7-n_s_WwrNC_8tQYLfhWKgmT_dDWwJw8ctA&s=jGwsu2zf5Pm3kG3GKLFFxalyi30aoXq_-izsMrEy_iQ&e=>),
but one aspect bugs me: It doesn't seem like import statements are remembered between script
invocations. This makes it far harder to use Groovy to prototype UIs within jAlbum's scripting
console than for instance BeanShell (using the javax.script API). We currently support the
slow BeanShell scripting language and JavaScript. BeanShell behaves well in this regard, remembering
earlier imported packages between script invocations. Can this be added to Groovy or is there
some API flag we can set?
>>  
>> Regards
>> /David, jAlbum founder and client lead developer.
> 

----------------------
Keith Suderman
Research Associate
Department of Computer Science
Vassar College, Poughkeepsie NY
suderman@cs.vassar.edu





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