Add support for fixed default element namespace (#2618)

* add support for `fixed default element namespace`

* refactoring of `QNmCache` and `QNmCheck` into `QNmResolver`

Author: GuntherRademacher

basex-core/src/main/java/org/basex/query/QueryParser.java

@@ -95,7 +95,7 @@ public class QueryParser extends InputParser {
   /** Output declarations. */
   private final HashMap<String, Object> sparams = new HashMap<>();
   /** QName cache. */
-  private final QNmCache qnames = new QNmCache();
+  private final QNmResolver qnames = new QNmResolver();
   /** Local variable. */
   private final LocalVars localVars = new LocalVars(this);
 
@@ -261,7 +261,7 @@ private void finish(final MainModule mm) throws QueryException {
     }
 
     // completes the parsing step
-    qnames.assignURI(this, 0);
+    qnames.resolve(this, 0, sc.elemNS);
     if(sc.elemNS != null) sc.ns.add(EMPTY, sc.elemNS, null);
     RecordType.resolveRefs(recordTypeRefs, namedRecordTypes);
   }
@@ -329,8 +329,10 @@ private void prolog1() throws QueryException {
     while(true) {
       final int p = pos;
       if(wsConsumeWs(DECLARE)) {
-        if(wsConsumeWs(DEFAULT)) {
-          if(!defaultNamespaceDecl() && !defaultCollationDecl() && !emptyOrderDecl() &&
+        if(wsConsumeWs(FIXED)) {
+          if(!wsConsumeWs(DEFAULT) || !defaultNamespaceDecl(true)) throw error(DECLINCOMPLETE);
+        } else if(wsConsumeWs(DEFAULT)) {
+          if(!defaultNamespaceDecl(false) && !defaultCollationDecl() && !emptyOrderDecl() &&
              !decimalFormatDecl(true)) throw error(DECLINCOMPLETE);
         } else if(wsConsumeWs(BOUNDARY_SPACE)) {
           boundarySpaceDecl();
@@ -529,10 +531,11 @@ private void boundarySpaceDecl() throws QueryException {
 
   /**
    * Parses the "DefaultNamespaceDecl" rule.
+   * @param fixed fixed default namespace flag
    * @return true if declaration was found
    * @throws QueryException query exception
    */
-  private boolean defaultNamespaceDecl() throws QueryException {
+  private boolean defaultNamespaceDecl(final boolean fixed) throws QueryException {
     final boolean elem = wsConsumeWs(ELEMENT);
     if(!elem && !wsConsumeWs(FUNCTION)) return false;
     wsCheck(NAMESPACE);
@@ -542,7 +545,9 @@ private boolean defaultNamespaceDecl() throws QueryException {
 
     if(elem) {
       if(!decl.add(ELEMENT)) throw error(DUPLNS);
+      sc.elemNsFixed = fixed;
       sc.elemNS = uri.length == 0 ? null : uri;
+      sc.dirNS = sc.elemNS;
     } else {
       if(!decl.add(FUNCTION)) throw error(DUPLNS);
       sc.funcNS = uri;
@@ -682,9 +687,13 @@ private void schemaImport() throws QueryException {
       prefix = ncName(NONAME_X, false);
       if(eq(prefix, XML, XMLNS)) throw error(BINDXML_X, prefix);
       wsCheck("=");
-    } else if(wsConsumeWs(DEFAULT)) {
-      wsCheck(ELEMENT);
-      wsCheck(NAMESPACE);
+    } else {
+      final boolean fixed = wsConsumeWs(FIXED);
+      if(fixed || wsConsumeWs(DEFAULT)) {
+        if(fixed) wsCheck(DEFAULT);
+        wsCheck(ELEMENT);
+        wsCheck(NAMESPACE);
+      }
     }
     final byte[] uri = uriLiteral();
     if(prefix != null && uri.length == 0) throw error(NSEMPTY);
@@ -2080,7 +2089,7 @@ private void validate() throws QueryException {
 
     if(consume(TYPE)) {
       final InputInfo ii = info();
-      qnames.add(eQName(SKIPCHECK, QNAME_X), ii);
+      qnames.add(eQName(SKIPCHECK, QNAME_X), sc, ii);
     }
     consume(STRICT);
     consume(LAX);
@@ -2462,7 +2471,7 @@ private ExprInfo simpleNodeTest(final Kind kind, final boolean all) throws Query
           }
         }
         // name test: prefix:name, name, Q{uri}name
-        qnames.add(name, kind == Kind.ELEMENT, ii);
+        if(kind == Kind.ELEMENT) qnames.add(name,  sc, ii); else qnames.add(name, false, ii);
         return nameTest.apply(name, scope);
       }
     }
@@ -3077,10 +3086,11 @@ private Expr dirElement(final boolean root) throws QueryException {
     // cache namespace information
     final int size = sc.ns.size();
     final byte[] nse = sc.elemNS;
+    final byte[] nsd = sc.dirNS;
     final int npos = qnames.size();
 
     final QNm name = new QNm(qnm);
-    qnames.add(name, ii);
+    qnames.add(name, true, ii);
 
     final Atts ns = new Atts();
     final ExprList cont = new ExprList();
@@ -3170,7 +3180,8 @@ private Expr dirElement(final boolean root) throws QueryException {
             sc.ns.add(prefix, uri);
           } else {
             if(eq(uri, XML_URI)) throw error(XMLNSDEF_X, uri);
-            sc.elemNS = uri;
+            sc.dirNS = uri;
+            if(!sc.elemNsFixed) sc.elemNS = sc.dirNS;
           }
           if(ns.contains(prefix)) throw error(DUPLNSDEF_X, prefix);
           ns.add(prefix, uri);
@@ -3201,7 +3212,7 @@ private Expr dirElement(final boolean root) throws QueryException {
       if(!eq(name.string(), close)) throw error(TAGWRONG_X_X, name.string(), close);
     }
 
-    qnames.assignURI(this, npos);
+    qnames.resolve(this, npos, sc.dirNS);
 
     // check for duplicate attribute names
     if(atts != null) {
@@ -3215,6 +3226,7 @@ private Expr dirElement(final boolean root) throws QueryException {
 
     sc.ns.size(size);
     sc.elemNS = nse;
+    sc.dirNS = nsd;
     return new CElem(info(), false, name, ns, cont.finish());
   }
 
@@ -3356,7 +3368,7 @@ private Expr compConstructor() throws QueryException {
   private Expr compElement() throws QueryException {
     final Expr name = compName(NOELEMNAME, true);
     if(name == null) return null;
-    if(name instanceof final QNm qnm) qnames.add(qnm, info());
+    if(name instanceof final QNm qnm) qnames.add(qnm, sc, info());
     skipWs();
     return current('{') ? new CElem(info(), true, name, new Atts(), enclosedExpr()) : null;
   }

basex-core/src/main/java/org/basex/query/QueryText.java

@@ -69,6 +69,7 @@ public interface QueryText {
   /** Parser token. */ String FALSE = "false";
   /** Parser token. */ String FINALLY = "finally";
   /** Parser token. */ String FIRST = "first";
+  /** Parser token. */ String FIXED = "fixed";
   /** Parser token. */ String FN = "fn";
   /** Parser token. */ String FOR = "for";
   /** Parser token. */ String FROM = "from";

basex-core/src/main/java/org/basex/query/StaticContext.java

@@ -36,8 +36,12 @@ public final class StaticContext {
 
   /** Default collation (default collection ({@link QueryText#COLLATION_URI}): {@code null}). */
   public Collation collation;
+  /** Default element/type namespace fixed flag. */
+  public boolean elemNsFixed;
   /** Default element/type namespace. */
   public byte[] elemNS;
+  /** Direct element constructor default element/type namespace (differs from above if "fixed"). */
+  public byte[] dirNS;
   /** Default function namespace. */
   public byte[] funcNS;
   /** Name of module (not assigned for main module). */
@@ -90,6 +94,7 @@ public StaticContext(final QueryContext qc) {
   void namespace(final String prefix, final String uri) throws QueryException {
     if(prefix.isEmpty()) {
       elemNS = uri.isEmpty() ? null : token(uri);
+      dirNS = elemNS;
     } else if(uri.isEmpty()) {
       ns.delete(token(prefix));
     } else {

basex-core/src/main/java/org/basex/query/util/parse/QNmCache.java

@@ -0,0 +1,81 @@
+package org.basex.query.util.parse;
+
+import static org.basex.query.QueryError.*;
+
+import java.util.*;
+
+import org.basex.query.*;
+import org.basex.query.value.item.*;
+import org.basex.util.*;
+
+/**
+ * Resolves namespace URIs of QNames whose resolution must be deferred until the surrounding
+ * namespace context is known.
+ *
+ * @author BaseX Team, BSD License
+ * @author Christian Gruen
+ */
+public final class QNmResolver {
+  /**
+   * Entry for a QName whose namespace URI still needs to be resolved.
+   * @param name QName to be resolved
+   * @param nsElem flag for assigning default element namespace
+   * @param info input info (can be {@code null})
+   */
+  private record Entry(QNm name, boolean nsElem, InputInfo info) { }
+  /** QNames to be resolved. */
+  private final ArrayList<Entry> entries = new ArrayList<>();
+
+  /**
+   * Adds a QName unless it already has a namespace URI or it can be immediately assigned the fixed
+   * default namespace URI. This method must not be called for the element names of direct element
+   * constructors.
+   * @param name QName
+   * @param sc static context
+   * @param info input info (can be {@code null})
+   */
+  public void add(final QNm name, final StaticContext sc, final InputInfo info) {
+    if(sc.elemNsFixed && !name.hasPrefix() && !name.hasURI()) name.uri(sc.elemNS);
+    else add(name, true, info);
+  }
+
+  /**
+   * Adds a QName unless it already has a namespace URI.
+   * @param name qname
+   * @param nsElem default check
+   * @param info input info (can be {@code null})
+   */
+  public void add(final QNm name, final boolean nsElem, final InputInfo info) {
+    if(!name.hasURI()) entries.add(new Entry(name, nsElem, info));
+  }
+
+  /**
+   * Finalizes the QNames by assigning namespace URIs.
+   * @param qp query parser
+   * @param npos first entry to be checked
+   * @param elemNS default element namespace
+   * @throws QueryException query exception
+   */
+  public void resolve(final QueryParser qp, final int npos, final byte[] elemNS)
+      throws QueryException {
+    for(int i = entries.size() - 1; i >= npos; --i) {
+      final Entry entry = entries.get(i);
+      if(entry.name.hasPrefix()) {
+        entry.name.uri(qp.sc.ns.uri(entry.name.prefix()));
+        if(npos == 0 && !entry.name.hasURI())
+          throw qp.error(NOURI_X, entry.info, entry.name.prefix());
+      } else if(entry.nsElem) {
+        entry.name.uri(elemNS);
+      }
+      if(entry.name.hasURI()) entries.remove(i);
+    }
+  }
+
+  /**
+   * Returns the number of remaining QNames.
+   * @return number
+   */
+  public int size() {
+    return entries.size();
+  }
+}