Saxon

I have run into a problem with the streamability analysis of some code with @for-each-group@ where the grouping population is created using @copy-of(foo)@ (which I had to do as the pattern in @group-starting-with@ is not motionless) and where inside of the @for-each-group@ I try to repeatedly access @current-group()@.

The sample stylesheet is

When I try to run that with Saxon-EE 9.7.0.8J from the command line the output is

Static error at xsl:template on line 14 column 30 of test201610160103.xsl:
  XTSE3430: Template rule is declared streamable but it does not satisfy the streamability rules.
  * The current-group() function is evaluated repeatedly
  * Predicate at line 20 is not motionless

Obviously there are several uses of @current-group()@ inside of the @for-each-group@ and the predicate @current-group()[1]/th[@scope = 'rowgroup']@ is not motionless but I am astonished that this matters given that the grouping population is created with @copy-of(tr)@ so that the body of the @for-each-group@ does not process any streamed nodes. Is Saxon rightly rejecting the code as not streamable given that the grouping population is created using @copy-of(tr)@?

Exselt happily compiles and runs the code without complaining about streamability but on the other hand it even does that when I simply use @<xsl:for-each-group select="tr" group-starting-with="tr[th[@scope = 'rowgroup']]">@ so I am not sure how meaningful Exselt's streamability analysis is.

An input sample is

	
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