Fix empty SPPF node from xearley ignore carry-over (fixes #1598)#1601
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When an item in to_scan was carried over past an ignored sequence with item.node=None (e.g. a prediction at ptr=0 that hasn't matched anything yet), the carry-over still allocated an empty SymbolNode and stored it in node_cache. That empty node later became the left child of a PackedNode when the terminal was finally scanned, and crashed ForestSumVisitor with "max() iterable argument is empty". Skip SymbolNode creation when item.node is None — there's nothing to merge, and new_item.node staying None makes the subsequent PackedNode have left=None, which is well-handled everywhere else.
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #1601 +/- ##
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Coverage 90.06% 90.06%
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Files 52 52
Lines 8089 8095 +6
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+ Hits 7285 7291 +6
Misses 804 804
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@chanicpanic Thanks! Btw did you see this PR? I did it on a lark (hah) and I'm not sure it's correct. But the performance gains are substantial. |
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I did see that one. I'm not familiar with the details of Joop Leo, but perhaps it is time for me to learn :) |
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When an item in to_scan was carried over past an ignored sequence with item.node=None (e.g. a prediction at ptr=0 that hasn't matched anything yet), the carry-over still allocated an empty SymbolNode and stored it in node_cache. That empty node later became the left child of a PackedNode when the terminal was finally scanned, and crashed ForestSumVisitor with "max() iterable argument is empty".
Skip SymbolNode creation when item.node is None — there's nothing to merge, and new_item.node staying None makes the subsequent PackedNode have left=None, which is well-handled everywhere else.