Created attachment 324256 [details]
files to reproduce refefime+indirect include problem

Fails in versions 2.9.1, 2.9.2 (did not try git master).

Attached is a ZIP with a minimal repro (distilled from a huge production schema). It still involves 4 separate files - could not make it smaller, sorry.

fruits-xt.xsd <- loading this as a schema fails. It uses "redefine" to extend two types: Apple and Orange.
fruits.xsd <- base schema - does not do much, uses "include" to load "types.xsd"
types.xds <- does nothing but includes types-extra.xsd, where Apple and Orange are defined
types-extra.xsd <- this is where datatypes Apple and Orange are actually defined

Error:

$ xmllint --schema fruits-xt.xsd blah
fruits-xt.xsd:19: element complexType: Schemas parser error : Element '{http://www.w3.org/2001/XMLSchema}complexType': The complex type definition '{http://garden.org/fruits}Orange' to be redefined could not be found in the redefined schema.
types-extra.xsd:9: element complexType: Schemas parser error : Element '{http://www.w3.org/2001/XMLSchema}complexType': A global complex type definition '{http://garden.org/fruits}Orange' does already exist.
WXS schema fruits-xt.xsd failed to compile
warning: failed to load external entity "blah"


Experiments:

1. if I make fruits.xsd include "types-extra.xsd" directly, no error
2. if I swap redefinitions in fruits-xt.xsd, will get similar message about Apple.

Looks like parser sees only the first data type declared in a file that is indirectly included.

FYI: Coming from LXML bug tracker: https://bugs.launchpad.net/lxml/+bug/1557710