Next steps ? (Re: An attempt of a CSR draft ... (Re: A new WIP (PR # 192) (Re: WIP version with PI compile (Re: A WIP for JDK-8238080 for review/discussion (Re: "Internal review ID 9063426: "FXMLLoader: if script engines implement javax.script.Compilabel compile scripts"

Rony G. Flatscher Rony.Flatscher at wu.ac.at
Mon May 11 12:12:09 UTC 2020 

Hi Kevin,

On 09.05.2020 17:16, Kevin Rushforth wrote:
> I'm finally getting back to this. I took a look at https://github.com/openjdk/jfx/pull/192 and I
> like that as the direction for this enhancement.
>
> The initial CSR you have is a good start.

Thank you!

> Next steps are:
>
> 1. Update the "Introduction to FXML" specification (see my comment in the PR)
> 2. Update PR 192 with the draft CSR as a comment, modifying it to include the above additions to
> "Introduction to FXML"
> 3. Remove WIP from the title
>
> You can then close the other two PRs (129 and 187).

will do (may take a little bit).

Cheers

---rony


> On 4/28/2020 6:15 AM, Rony G. Flatscher wrote:
>>
>> Hi Kevin,
>>
>> what should be the next steps?
>>
>> Should I remove "WIP" from the title in <https://github.com/openjdk/jfx/pull/192> and add the CSR
>> draft text of my last e-mail as a "CSR" comment with PR # 192, thereby requesting it to be added
>> to <https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8238080>?
>>
>> Please advise.
>>
>> TIA,
>>
>> ---rony
>>
>> P.S.: This is the RFE:
>>
>>   * RFE (2020-01-24): <https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8238080>
>>
>> These are the three versions (all with appropriate unit tests) that I came up with
>> chronologically to implement the RFE, would prefer the latest version (PR # 192):
>>
>>   * Compile if Compilable implemented (2020-02-28): <https://github.com/openjdk/jfx/pull/129>
>>   * Compile if compile PI and Compilable is implemented (2020-04-11):
>>     <https://github.com/openjdk/jfx/pull/187>
>>   * Compile with fallback, if Compilable is implemented, compile PI for fine-grained control
>>     (2020-04-14): <https://github.com/openjdk/jfx/pull/192>
>>
>>
>> On 22.04.2020 20:01, Rony G. Flatscher wrote:
>>> Hi Kevin,
>>>
>>> as I am not able to file a CSR with the issue you suggested to come up with a draft, so here it goes:
>>>
>>>     Summary
>>>     =======
>>>     Have javafx.fxml.FXMLLoader compile FXML scripts before evaluating them, if the script engine
>>>     implements the javax.script.Compilable interface to speed up execution. In case compilation
>>>     throws a javax.script.ScriptException fall back to evaluating the uncompiled script. Allow
>>>     control of script compilation with a "compile" PI for FXML files.
>>>
>>>     Problem
>>>     =======
>>>     javafx.fxml.FXMLLoader is able to execute scripts in Java script languages
>>>     (javax.script.ScriptEngine implementations) referred to or embedded in a FXML file.
>>>
>>>     If a script engine implements the javax.script.Compilable interface, then such scripts could be
>>>     compiled and the resulting javax.script.CompiledScript could be executed instead using its
>>>     eval() methods.
>>>
>>>     Evaluating the javax.script.CompiledScript objects may help speed up the execution of script
>>>     invocations, especially for scripts defined for event attributes in FXML elements (e.g. like
>>>     onMouseMove) which may be repetitively invoked and evaluated.
>>>
>>>     Solution 
>>>     ========
>>>     Before evaluating the script code test whether the javax.script.ScriptEngine implements
>>>     javax.script.Compilable. If so, compile the script to a javax.script.CompiledScript object first
>>>     and then use its eval() method to evaluate the script, otherwise continue to use the
>>>     javax.script.ScriptEngine's eval() method instead. Should compilation of a script yield
>>>     (unexpectedly) a javax.script.ScriptException then fall back to using the
>>>     javax.script.ScriptEngine's eval() method. A new process instruction "compile" allows control of
>>>     the compilation of scripts ("true" sets compilation on, "false" to set compilation off) in FXML
>>>     files.
>>>
>>>     Specification
>>>     =============
>>>     If a javax.script.ScriptEngine implements the javax.script.Compilable interface, then use its
>>>     compile() method to compile the script to a javax.script.CompiledScript object and use its
>>>     eval() method to run the script. In the case that the compilation throws (unexpectedly) a
>>>     javax.script.ScriptException log a warning and fall back to using the
>>>     javax.script.ScriptEngine's eval() method instead.
>>>     To allow setting this feature off and on while processing the FXML file a "compile" process
>>>     instruction ("<?compile false?>" or "<?compile true?>") gets defined that allows to turn
>>>     compilation off and on throughout a FXML file.
>>>
>>> Having never seen a real CSR I hope that this matches what is expected and is helpful for
>>> assessment. If not please advise (got the name of these fields from [1]).
>>>
>>> ---
>>>
>>> Also added brief information about the respective test units (what they test and yield) in the WIP  [2].
>>>
>>> ---rony
>>>
>>> [1] "CSR-FAQ": <https://wiki.openjdk.java.net/display/csr/CSR+FAQs>
>>>
>>> [2] "WIP: Script compilable+compile PI+fallback: 8238080: FXMLLoader: if script engines implement
>>> javax.script.Compilable compile scripts #192":  <https://github.com/openjdk/jfx/pull/192>
>>>
>>>
>>> On 20.04.2020 14:58, Rony G. Flatscher wrote:
>>>> There is a new WIP at <https://github.com/openjdk/jfx/pull/192>:
>>>>
>>>>     This WIP adds the ability for a fallback in case compilation of scripts fails, in which case a
>>>>     warning gets issued about this fact and evaluation of the script will be done without
>>>>     compilation. Because of the fallback scripts get compiled with this version by default. It
>>>>     extends PR 187 #187.
>>>>
>>>>     To further ease spotting scripts that cause a ScriptException a message in the form of
>>>>     "filename: caused ScriptException" gets added to the exception handling in either of the three
>>>>     locations: an error message, a stack trace or a wrap-up into a RuntimeException (having three
>>>>     different kinds of reporting ScriptExceptions may be questioned, however none of these tear down
>>>>     the FXML GUI).
>>>>
>>>> This WIP comes with proper test units as well. As per Kevin's suggestion a warning gets logged
>>>> whenever a script cannot be compiled and the fallback gets used.
>>>>
>>>> It is suggested to use this WIP as it includes the compilation by default with a safe fallback to
>>>> evaluate the uncompiled script, if compilation (unexpectedly) fails.
>>>>
>>>> Again, any feedback, discussion welcome!
>>>>
>>>> ---rony
>>>>
>>>> P.S.: In the log history there is a commit message "Make message more pregnant.", it should have
>>>> read "Make messages more terse." instead|.||
>>>> |
>>>>
>>>>
>>>> On 17.04.2020 19:37, Rony G. Flatscher wrote:
>>>>> There is a new WIP at <https://github.com/openjdk/jfx/pull/187> which adds a compile PI (process
>>>>> instruction) for turning on and off script compilation if the script engine implements the
>>>>> Compilable interface.
>>>>>
>>>>> By default compilation is off (no compilation), such that one needs to add a compile PI
>>>>> ("<?compile?>") at the top to activate this feature. Supplying "true" (default) or "false" as the PI
>>>>> data turns this feature on and off.
>>>>>
>>>>> The WIP comes with adapted test units that test "compile on" for an entire fxml file, "compile off",
>>>>> alternating using "compile on and off", and alternating using "compile off and on". This will test
>>>>> all variants of applying the compile PI for all categories of scripts.
>>>>>
>>>>> Any feedback appreciated!
>>>>>
>>>>> ---rony
>>>>>
>>>>> P.S.: FXML files that contain unknown PIs do not cause a runtime error by FXMLLoader, they just get
>>>>> ignored. Therefore one could apply the compile PI to FXML files that are used in older JavaFX runtimes.
>>>>>
>>>>> P.P.S.: In the next days I will also add Kevin's idea in a separate version that will have a
>>>>> fallback solution in case a compilation is (unexpectedly) not successful, reverting to
>>>>> (interpretative) evaluation/execution of the script. In that version it is planned to have
>>>>> compilation on by default as in the case of a compilation failure there will be a safe backup solution.
>>>>>
>>>>>
>>>>> On 14.04.2020 19:52, Kevin Rushforth wrote:
>>>>>> Yes, I agree that enough time has gone by. Go ahead with your proposal. I would wait a bit to
>>>>>> create the CSR until the review is far enough along to know which direction we intend to go.
>>>>>>
>>>>>> Unless there is a real concern about possible regressions if scripts are compiled by default, I
>>>>>> think "enabled by default" is the way to go. Your argument that such script engines are broken
>>>>>> seems reasonable, since this only applies to script engines that implement javax.script.Compilable
>>>>>> in the first place. We still might want to add way to turn compilation off for individual scripts.
>>>>>> One other thing to consider is that if compilation fails, it might make sense to log a warning and
>>>>>> fall back to the existing interpreted mode.
>>>>>>
>>>>>> Does anyone else have any concerns with this?
>>>>>>
>>>>>> -- Kevin
>>>>>>
>>>>>>
>>>>>> On 4/14/2020 9:48 AM, Rony G. Flatscher wrote:
>>>>>>> Hi there,
>>>>>>>
>>>>>>> as there was probably enough time that has passed by I would intend to create a CSR in the next days
>>>>>>> with the PR as per Kevin's suggestion.
>>>>>>>
>>>>>>> (For the case that this feature should not be active by default, the CSR will suggest to define a
>>>>>>> new "compile" PI in the form <?compile [true|false] ?> (default, if no PI data given: true), which
>>>>>>> is independent of the existence of a language PI (this way it becomes also possible to allow
>>>>>>> compilation of external scripts denoted with the script-element, which do not need a page language
>>>>>>> to be set as the file's extension allows the appropriate script engine to be loaded and used for
>>>>>>> execution). A compile-PI would allow for turning compilation of scripts on by just adding the PI
>>>>>>> <?compile?> or <?compile true?>  to FXML files (and <?compile false?> to turn off), which seems to
>>>>>>> be simple and self-documentary. In general employing such compile PIs allows for setting compilation
>>>>>>> of scripts on and off throughout an FXML file.)
>>>>>>>
>>>>>>> ---rony
>>>>>>>
>>>>>>>
>>>>>>> On 04.04.2020 18:03, Rony G. Flatscher wrote:
>>>>>>>
>>>>>>>> Hi Kevin,
>>>>>>>>
>>>>>>>> On 03.04.2020 01:21, Kevin Rushforth wrote:
>>>>>>>>> I see that you updated the PR and sent it for review.
>>>>>>>>>
>>>>>>>>> Before we formally review it in the PR, let's finish the discussion as to whether this is a useful
>>>>>>>>> feature, and if so, what form this feature should take.
>>>>>>>>>
>>>>>>>>>  From my point of view, this does seem like a useful feature. Would other users of FXML benefit
>>>>>>>>> from it?
>>>>>>>> Script code should be executed faster after compilation, so any FXML page that hosts script code
>>>>>>>> may
>>>>>>>> benefit.
>>>>>>>>
>>>>>>>> The benefits depend on the type of script (and maybe its size and its complexity) and also on the
>>>>>>>> types of event handlers the scripts serve, e.g. move or drag event handlers may benefit
>>>>>>>> significantly. This is because repeated invocation of compiled script event handlers do not cause
>>>>>>>> the reparsing of that script's source and interpreting it on each invocation, which may be
>>>>>>>> expensive
>>>>>>>> depending on the script engine, but rather allows the immediate evaluation/execution of the
>>>>>>>> compiled
>>>>>>>> script by the script engine.
>>>>>>>>
>>>>>>>>> I'm not certain whether we want it to be implicit, compiling the script if the script engine in
>>>>>>>>> question implements Compilable, or via a new keyword or tag. What are the pros / cons?
>>>>>>>> In principle there are three possibilities:
>>>>>>>>
>>>>>>>>      1) If a script engine implements javax.script.Compilable, compile the script and execute the
>>>>>>>>      compiled version. In the case of event handlers compile and buffer the compiled script and
>>>>>>>>      execute the compiled script each time its registered event fires.
>>>>>>>>
>>>>>>>>        o Pro: immediately benefits all existing FXML pages that host scripts
>>>>>>>>        o Con: it is theoretically possible (albeit quite unlikely) that there are scripts that fail
>>>>>>>>          compiling but have been employed successfully in interpreted mode
>>>>>>>>
>>>>>>>>      2) Introduce some form of an optional attribute (e.g. "compile={true|false}") to the FXML
>>>>>>>>      language PI that switches on compilation of scripts hosted in FXML definitions if the script
>>>>>>>>      engine implements the javax.script.Compilable interface. If missing it would default to
>>>>>>>> "false".
>>>>>>>>      (Alternatively, add a "compile" PI, that if present causes the compilation of scripts, if the
>>>>>>>>      script engine supports it. It would be an error if the "compile" PI was present, but the
>>>>>>>>      "language" PI was not.)
>>>>>>>>
>>>>>>>>        o Pro: compilation of FXML hosted scripts is done only, if the FXML definition of the
>>>>>>>> language
>>>>>>>>          PI gets changed
>>>>>>>>        o Con: benefit not made available automatically to existing FXML pages that host scripts
>>>>>>>>
>>>>>>>>      3) Another possibility would be to define a boolean attribute/property "compile" for script
>>>>>>>> and
>>>>>>>>      node elements and only compile the scripts, if the property is set to true
>>>>>>>>
>>>>>>>>        o Pro: compilation of FXML hosted scripts is done only, if the FXML definition gets changed
>>>>>>>>          accordingly
>>>>>>>>        o Con: potential benefit not made available automatically to existing FXML pages that
>>>>>>>> host scripts
>>>>>>>>
>>>>>>>> 2 and 3 could be combined, where 2 would define the default compilation behavior that then could be
>>>>>>>> overruled individually by 3.
>>>>>>>>
>>>>>>>> The question would be whether 2 or/and 3 are really necessary as it can be expected that
>>>>>>>> compilation
>>>>>>>> of scripts by the script engines would find the same errors as while interpreting the very same
>>>>>>>> scripts (if not, the script engine is badly broken and it could be argued that then the
>>>>>>>> interpretation part of the script engine might be expected to be broken as well which would be
>>>>>>>> quite
>>>>>>>> dangerous from an integrity POV; the same consideration applies as well if the execution of the
>>>>>>>> compiled script would behave differently to interpreting the very same script by the same script
>>>>>>>> engine).
>>>>>>>>
>>>>>>>> The current WIP implements 1 above and includes an appropriate test unit.
>>>>>>>>
>>>>>>>>> What do others think?
>>>>>>>>> In either case, we would need to make sure that this doesn't present any security concerns in the
>>>>>>>>> presence of a security manager. As long as a user-provided class is on the stack, it will be fine,
>>>>>>>>> but we would need to ensure that.
>>>>>>>> The compilation of scripts needs to be done by the Java script engines (implementing both,
>>>>>>>> javax.script.Engine and javax.script.Compilable) as well as controlling the execution of compiled
>>>>>>>> scripts ([javax.script.CompiledScript]
>>>>>>>> (https://docs.oracle.com/en/java/javase/14/docs/api/java.scripting/javax/script/CompiledScript.html)).
>>>>>>>>
>>>>>>>>
>>>>>>>> ---rony
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>> On 4/2/2020 10:41 AM, Rony G. Flatscher wrote:
>>>>>>>>>> After merging master, applying some fixes and changing the title to reflect the change from
>>>>>>>>>> WIP to a
>>>>>>>>>> pull request I would kindly request a review of this pull request!
>>>>>>>>>>
>>>>>>>>>> Here the URL: <https://github.com/openjdk/jfx/pull/129>, title changed to: "8238080:
>>>>>>>>>> FXMLLoader: if
>>>>>>>>>> script engines implement javax.script.Compilable compile scripts".
>>>>>>>>>>
>>>>>>>>>> ---rony
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On 28.02.2020 19:22, Rony G. Flatscher wrote:
>>>>>>>>>>> Here is a WIP [1] implementation of [2]. The WIP is based on [3], which is currently in
>>>>>>>>>>> review, and
>>>>>>>>>>> has an appropriate test unit going with it as well, please review.
>>>>>>>>>>>
>>>>>>>>>>> There should be no compatibility issue with this implementation.
>>>>>>>>>>>
>>>>>>>>>>> Discussion: another solution could be to not compile by default. Rather compile, if some new
>>>>>>>>>>> information is present with the FXML file which cannot possibly be present in existing FXML
>>>>>>>>>>> files.
>>>>>>>>>>> In this scenario one possible and probably simple solution would be to only compile scripts
>>>>>>>>>>> if the
>>>>>>>>>>> language process instruction (e.g. <?language rexx?>) contains an appropriate attribute with a
>>>>>>>>>>> value
>>>>>>>>>>> indicating that compilation should be carried out (e.g.: compile="true"). This way only FXML
>>>>>>>>>>> with
>>>>>>>>>>> PIs having this attribute set to true would be affected. If desired I could try to come up
>>>>>>>>>>> with a
>>>>>>>>>>> respective solution as well.
>>>>>>>>>>>
>>>>>>>>>>> ---rony
>>>>>>>>>>>
>>>>>>>>>>> [1] "Implementation and test unit": <https://github.com/openjdk/jfx/pull/129>
>>>>>>>>>>>
>>>>>>>>>>> [2] "JDK-8238080 : FXMLLoader: if script engines implement javax.script.Compilable compile
>>>>>>>>>>> scripts":
>>>>>>>>>>> <https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8238080>
>>>>>>>>>>>
>>>>>>>>>>> [3] "8234959: FXMLLoader does not populate ENGINE_SCOPE Bindings with FILENAME and ARGV":
>>>>>>>>>>> <https://github.com/openjdk/jfx/pull/122/commits>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On 24.01.2020 16:26, Kevin Rushforth wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Thank you for filing this enhancement request. As an enhancement it should be discussed on this
>>>>>>>>>>>> list before proceeding with a pull request (although a "WIP" or Draft PR can be used to
>>>>>>>>>>>> illustrate
>>>>>>>>>>>> the concept).
>>>>>>>>>>>>
>>>>>>>>>>>> For my part, this seems like a reasonable enhancement, as long as there are no compatibility
>>>>>>>>>>>> issues, but it would be good to hear from application developers who heavily use FXML.
>>>>>>>>>>>>
>>>>>>>>>>>> -- Kevin
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> On 1/24/2020 7:21 AM, Rony G. Flatscher wrote:
>>>>>>>>>>>>> Just filed a RFE with the following information:
>>>>>>>>>>>>>
>>>>>>>>>>>>>      * Component:
>>>>>>>>>>>>>          o JavaFX
>>>>>>>>>>>>>
>>>>>>>>>>>>>      * Subcomponent:
>>>>>>>>>>>>>          o fxml: JavaFX FXML
>>>>>>>>>>>>>
>>>>>>>>>>>>>      * Synopsis:
>>>>>>>>>>>>>          o "FXMLLoader: if script engines implement javax.script.Compilabel compile scripts"
>>>>>>>>>>>>>
>>>>>>>>>>>>>      * Descriptions:
>>>>>>>>>>>>>          o "FXMLLoader is able to execute scripts in Java script languages
>>>>>>>>>>>>> (javax.script.ScriptEngine
>>>>>>>>>>>>>            implementations) if such a Java script language gets defined as the controller
>>>>>>>>>>>>> language in
>>>>>>>>>>>>>            the FXML file.
>>>>>>>>>>>>>
>>>>>>>>>>>>>            If a script engine implements the javax.script.Compilable interface, then such
>>>>>>>>>>>>> scripts
>>>>>>>>>>>>> could
>>>>>>>>>>>>>            be compiled and the resulting javax.script.CompiledScript could be executed instead
>>>>>>>>>>>>> using
>>>>>>>>>>>>>            its eval() methods.
>>>>>>>>>>>>>
>>>>>>>>>>>>>            Evaluating the CompiledScript objects may help speed up the execution of script
>>>>>>>>>>>>> invocations,
>>>>>>>>>>>>>            especially for scripts defined for event attributes in FXML elements (e.g. like
>>>>>>>>>>>>> onMouseMove)
>>>>>>>>>>>>>            which may be repetitevly invoked and evaluated."
>>>>>>>>>>>>>
>>>>>>>>>>>>>      * System /OS/Java Runtime Information:
>>>>>>>>>>>>>          o "All systems."
>>>>>>>>>>>>>
>>>>>>>>>>>>> Received the internal review ID: "9063426"
>>>>>>>>>>>>>
>>>>>>>>>>>>> ---rony

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