Tree API: offsets for String fields

[Emilian Bold]

Assuming I don't need some special permissions to do that (do I?) I could
expand the previous email and post it as an enhancement on
https://bugs.openjdk.java.net

But I'm also trying to understand the logic behind what you have.

The way I see it any AST node has some underlying tokens so its offsets
should be based on that.

Take VariableTree. The Javadoc mentions:

var name initializer ;

but I assume the offset ranges are something like

var [name = [initializer]] ;

So, 'var' and whatever whitespace there is in between is ignored. The
'name' offsets are not explicit but may be inferred.

(A similar problem with FunctionDeclarationTree.)

What I would do with Variable Tree would be to have the offset ranges like:

[var [name] = [initializer]]

with the VariableTree covering everything ('var' too) and 'name' having a
separate IdentifierTree.

Continue/BreakTree/LabeledStatementTree are not really that important/used
so if there is no internal info it's no big loss.

--emi


On Thu, May 12, 2016 at 7:19 PM, Sundararajan Athijegannathan <
sundararajan.athijegannathan at oracle.com> wrote:

> Hi,
>
> Thanks for your comments. Nashorn Parser API was modeled after similar
> API provided by javac - for consistency sake and to leverage developer
> familiarity.  For example, ContinueTree, MemberSelectTree of javac Tree
> API:
>
>
> https://docs.oracle.com/javase/8/docs/jdk/api/javac/tree/com/sun/source/tree/ContinueTree.html
>
>
> https://docs.oracle.com/javase/8/docs/jdk/api/javac/tree/com/sun/source/tree/MemberSelectTree.html
>
> I agree that consistency should not result in API 'mistakes/gaps' being
> propagated here.  BTW, labels are maintained as strings even
> internally.  Member select property, Variable name , Function name etc.
> are all identifiers and so it is possible to make API return
> IdentifierTree objects. Will you please collect whatever you found and
> file a bug/enhancement for Nashorn parser API?
>
> Thanks,
>
> -Sundar
>
>
> On 5/12/2016 9:10 PM, Emilian Bold wrote:
> > Hello,
> >
> > It's really important for a Javascript editor to know the offsets of each
> > syntax tree node and of whatever the node contains (I'm not really saying
> > tokens but... constituent parts and keywords are the minimum).
> >
> > So it would be great to provide or document how offsets are to be
> computed
> > for the String fields from the Nashorn Tree API.
> >
> > (Ideally the API could also be changed to use an IdentifierTree or some
> > other Tree subclass which provides the start/endPosition.)
> >
> > A few examples:
> >
> > * MemberSelectTree has a String getIdentifier. Since I *assume* that the
> > MemberSelectTree.getEndPosition is right after the identifier, I have to
> > subtract the identifier length to get the identifier start offset.
> >
> > * VariableTree has a String getName(). It seems to me that
> > VariableTree.getStartPosition is the 'name' startPosition. This also
> means
> > you cannot really know where 'var' actually is -- it could be on another
> > line altogether; it's also odd to me that 'var' is outside the [start,
> end]
> > range for the VariableTree.
> >
> > * ContinueTree and BreakTree both have a String getLabel
> >
> > * LabeledStatementTree has a String getLabel
> >
> > * FunctionExpressionTree and FunctionDeclarationTree both have a String
> > getName but I'm not sure how the offset for that is computed. Also not
> sure
> > how the offset of the 'function' keyword would be computed.
> >
> > Could somebody explain this to me? I'll make a nice list for future
> > reference.
> >
> > --emi
>
>