Sascha Brawer 1ddfe24338 [feaLib] Support multiple chain contexts after ignore sub
Although this construct is in violation of the `ignore sub` grammar
given by the current OpenType Feature File syntax specification,
the very same specification document illustrates (in example 3
of section 5.f.ii) the `ignore sub` statement with a comma-separated
list of backgrack/input/lookahead triples.

See https://github.com/adobe-type-tools/afdko/issues/105 for a request
to amend the OpenType Feature File syntax specification.

After this code change, feaLib can now parse testdata/spec5f_ii_3.fea;
the output is identical to what is generated by Adobe's makeotf tool.

https://github.com/behdad/fonttools/issues/503
2016-02-05 11:02:29 +01:00

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# OpenType Feature File specification, section 5.f.ii, example 3
# "Specifying exceptions to the Chain Sub rule"
# http://www.adobe.com/devnet/opentype/afdko/topic_feature_file_syntax.html
feature test {
@LETTER = [a-z];
ignore substitute @LETTER a' n' d', a' n' d' @LETTER;
substitute a' n' d' by a_n_d;
} test;