Steve Rowe commented on LUCENE-4065:

bq. But your testcase argues that this should be 4 positions (1 + 2 + 1). I'm 
just not convinced thats the correct behavior: its unintuitive to me that a 
stopfilter would make a document "longer" in the sense of actually adding 
additional positions... (no, it doesn't impact length normalization because 
this value isn't used for that, but its just really confusing).

Yeah I think my testcase is just wrong - StopFilter's behavior actually looks 
correct here to me (testcase can be fixed by changing the "walking" posinc  
{{2}} -> {{1}}, which no longer fails).  I guess I misinterpreted Jim's example 
as graph corruption, which this doesn't look like to me.

> FilteringTokenFilter should never corrupt the tokenstream graph
> ---------------------------------------------------------------
>                 Key: LUCENE-4065
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4065
>             Project: Lucene - Core
>          Issue Type: Bug
>          Components: modules/analysis
>            Reporter: Robert Muir
>            Priority: Major
>         Attachments: LUCENE-4065_test.patch
> Currently removers like stopfilter have an option (true/false) to enable 
> position increments.
> If its true: it both inserts gaps where necessary AND propagates gaps down 
> the stream.
> If its false: it does neither, which can totally mess up the tokenstream 
> graph (e.g. move synonyms to another word).
> There are totally valid natural usecases for false, where you don't want gaps 
> because you want phrasequeries to act as if the word was never actually there.
> But 'not inserting gaps' is separate from proper propagation of existing gaps.
> So I think we should provide an option (either fix 'false' or make it an 
> enum), where you still get a legit tokenstream and dont totally screw it up, 
> but you simply omit gaps.
> See LUCENE-3848 for more information (Where we at least fixed this case to 
> not begin the tokenstream with posinc=0)

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