XML missing encoding error

basis/xml/autoencoding/autoencoding.factor

@@ -3,7 +3,7 @@
 USING: kernel namespaces xml.name io.encodings.utf8 xml.elements
 io.encodings.utf16 xml.tokenize xml.state math ascii sequences
 io.encodings.string io.encodings combinators accessors
-xml.data io.encodings.iana ;
+xml.data io.encodings.iana xml.errors ;
 IN: xml.autoencoding
 
 : decode-stream ( encoding -- )
@@ -35,7 +35,10 @@ IN: xml.autoencoding
 
 : prolog-encoding ( prolog -- )
     encoding>> dup "UTF-16" =
-    [ drop ] [ name>encoding [ decode-stream ] when* ] if ;
+    [ drop ] [
+        dup name>encoding
+        [ decode-stream ] [ bad-encoding ] ?if
+    ] if ;
 
 : instruct-encoding ( instruct/prolog -- )
     dup prolog?

basis/xml/errors/errors-tests.factor

@@ -1,5 +1,5 @@
 USING: continuations xml xml.errors tools.test kernel arrays
-xml.data quotations fry ;
+xml.data quotations fry byte-arrays ;
 IN: xml.errors.tests
 
 : xml-error-test ( expected-error xml-string -- )
@@ -40,3 +40,4 @@ T{ bad-doctype f 1 22 T{ opener { name T{ name f "" "foo" "" } } { attrs T{ attr
 T{ disallowed-char f 1 4 1 } "<x>\u000001</x>" xml-error-test
 T{ missing-close f 1 8 } "<!-- foo" xml-error-test
 T{ misplaced-directive f 1 9 "ENTITY" } "<!ENTITY foo 'bar'><x/>" xml-error-test
+[ "<?xml version='1.0' encoding='foobar'?>" >byte-array bytes>xml ] [ T{ bad-encoding f 1 39 "foobar" } = ] must-fail-with

basis/xml/errors/errors.factor

@@ -338,5 +338,14 @@ TUPLE: bad-doctype < xml-error-at contents ;
 M: bad-doctype summary
     call-next-method "\nDTD contains invalid object" append ;
 
+TUPLE: bad-encoding < xml-error-at encoding ;
+: bad-encoding ( encoding -- * )
+    \ bad-encoding xml-error-at
+        swap >>encoding
+    throw ;
+M: bad-encoding summary
+    call-next-method
+    "\nEncoding in XML document does not exist" append ;
+
 UNION: xml-error
     multitags notags pre/post-content xml-error-at ;