Tree API: offsets for String fields

[Sundararajan Athijegannathan]

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