Hi everybody For now I cannot post code to reproduce this problem because it only occurs with one columns of a specific grid from a big application and so far I wasn't able to extract the code to reproduce the error into a runnable example. But after posting this I will keep trying and if I manage I will post that.
We migrated this web application from Java 1.7 + Tapestry 5.3.7 to Java 1.8 with Tapestry 5.3.8 . Clicking on the column header of this column - which contains String values - causes the exception below. While I'm investigating this error I was wondering if someone is aware of differences in the grid sorting of Tapestry 5.3.8 that might cause it to throw a null-pointer where Tapestry 5.3.7 wouldn't (and maybe should; it's likely that there is a mistake of mine that was somehow being "forgiven" by 5.3.7). Stacktrace: java.lang.NullPointerException ? org.apache.tapestry5.internal.grid.CollectionGridDataSource$2.compare(CollectionGridDataSource.java:78) ? org.apache.tapestry5.internal.grid.CollectionGridDataSource$3.compare(CollectionGridDataSource.java:91) ? java.util.TimSort.countRunAndMakeAscending(TimSort.java:355) ? java.util.TimSort.sort(TimSort.java:234) ? java.util.Arrays.sort(Arrays.java:1512) ? java.util.ArrayList.sort(ArrayList.java:1454) ? java.util.Collections.sort(Collections.java:175) ? org.apache.tapestry5.internal.grid.CollectionGridDataSource.prepare(CollectionGridDataSource.java:97) ? my.package.gui.tapestry.components.AMCGridEmbedded$CachingDataSource.prepare(AMCGridEmbedded.java:853) ? my.package.gui.tapestry.components.AMCGridEmbedded.setupDataSource(AMCGridEmbedded.java:1174) ? my.package.gui.tapestry.components.AMCGridEmbedded.setupRender(AMCGridEmbedded.java:655) ? my.package.gui.tapestry.components.AMCGridEmbedded.advised$setupRender_1a14d3f8fd924(AMCGridEmbedded.java) ? my.package.gui.tapestry.components.AMCGridEmbedded$Invocation_setupRender_1a14d3f8fd923.proceedToAdvisedMethod(Unknown Source) ? org.apache.tapestry5.internal.plastic.AbstractMethodInvocation.proceed(AbstractMethodInvocation.java:84) ? .... ? ....
