Pipleline Execution Stack Trace (was Cocoon Stack Traces)

[Christopher Oliver]

There are several issues with getting a meaningful stack trace from the 
execution of the pipeline:

1) The pipeline itself is not executed by the TreeProcessor but instead 
by a Pipeline processor. The sitemap source locations of the pipeline 
elements are not currently available to the ProcessingPipeline..
2) Source location information of the input to each pipeline stage is 
normally lost during the transformation steps.

So I would propose something like the following:

1) Have the TreeProcessor pass the sitemap source location in 
setGenerator(), addTransformer(), and setSerializer() to the 
ProcessingPipeline.
2) In "Debug" mode instrument the PipelineProcessor to write the output 
of each stage to a temporary file and regenerate SAX events from the 
temporary file (with location information). The PipelineProcessor would 
catch any exception thrown by a pipeline component and generate a 
"Cocoon" stack trace that includes the source location of the temp file. 
The Cocoon error reporter could even display the source code (maybe in 
tab-panes or whatever) of the pipeline intermediate results together 
with the stack trace. Hypothetically the label or tooltip on the 
tab-pane would be something like:

C:\TEMP\Pipeline_1060734815693.xml (output of 
C:\cocoon\build\webapp\samples\sitemap.xmap::66:16)

where the sitemap location refers to a <map:generate> or <map:transform> 
instruction.

WDYT?

Chris