Indices are not compatible with prevent-feeding

[joanise]

Given the mapping

a{1}b{2},c{2}d{1}

converting ab correctly outputs cd unless prevent-feeding is true, in which case it outputs c{2}d{1}

To reproduce, make a single-rule mapping in g2p-studio with In=a{1}b{2} and Out=c{2}d{1} and click on the prevent-mapping checkbox for that rule. Set the input to ab at the top.

[joanise]

The problem occurs whether the individual rule has prevent-feeding or the entire mapping has it.

[joanise]

PS: I noticed this problem when I was trying to improve kwk BOAS->Umista for the casing PR #274.

With rule uâ,uʼo and input UÂ we get these elements in tg.substring_alignments() (used in preserve_case()): [('U', 'u'), ('A', 'ʼ'), ('̂', 'o')] and therefore this output: Uʼo because the A is not aligned to the o and therefore does not cause it to get uppercased.

I figured I might be able to fix this with indices, changing uâ,uʼo to u{1}â{2},uʼ{1}o{2}, but this mapping has prevent feeding on so I get Uʼ{1}o{2} instead of the UʼO I'm trying to get.