Overlay: Discard base XML entities in overlay extracted files

Author: kaspersv

java/ql/lib/semmle/code/java/Overlay.qll

@@ -102,3 +102,31 @@ private predicate discardBaseConfigLocatable(@configLocatable el) {
   // property files than those included in overlayChangedFiles.
   overlayConfigExtracted(baseConfigLocatable(el))
 }
+
+/**
+ * An `@xmllocatable` that should be discarded in the base variant if its file is
+ * extracted in the overlay variant.
+ */
+overlay[local]
+abstract class DiscardableXmlLocatable extends @xmllocatable {
+  /** Gets the raw file for an xmllocatable in base. */
+  string getRawFileInBase() { not isOverlay() and result = getRawFile(this) }
+
+  /** Gets a textual representation of this discardable xmllocatable. */
+  string toString() { none() }
+}
+
+overlay[local]
+private predicate overlayXmlExtracted(string file) {
+  isOverlay() and
+  exists(@xmllocatable el | not files(el, _) and not xmlNs(el, _, _, _) and file = getRawFile(el))
+}
+
+overlay[discard_entity]
+private predicate discardXmlLocatable(@xmllocatable el) {
+  overlayChangedFiles(el.(DiscardableXmlLocatable).getRawFileInBase())
+  or
+  // The XML extractor is currently not incremental and may extract more
+  // XML files than those included in overlayChangedFiles.
+  overlayXmlExtracted(el.(DiscardableXmlLocatable).getRawFileInBase())
+}

java/ql/lib/semmle/code/xml/XML.qll

@@ -71,12 +71,12 @@ private module Input implements InputSig<File, Location> {
 
 import Make<File, Location, Input>
 
-private class DiscardableXmlAttribute extends DiscardableLocatable, @xmlattribute { }
+private class DiscardableXmlAttribute extends DiscardableXmlLocatable, @xmlattribute { }
 
-private class DiscardableXmlElement extends DiscardableLocatable, @xmlelement { }
+private class DiscardableXmlElement extends DiscardableXmlLocatable, @xmlelement { }
 
-private class DiscardableXmlComment extends DiscardableLocatable, @xmlcomment { }
+private class DiscardableXmlComment extends DiscardableXmlLocatable, @xmlcomment { }
 
-private class DiscardableXmlCharacters extends DiscardableLocatable, @xmlcharacters { }
+private class DiscardableXmlCharacters extends DiscardableXmlLocatable, @xmlcharacters { }
 
-private class DiscardableXmlDtd extends DiscardableLocatable, @xmldtd { }
+private class DiscardableXmlDtd extends DiscardableXmlLocatable, @xmldtd { }