[MOD] XQuery, destructuring records. qtspecs#2764

Author: ChristianGruen

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

@@ -1573,7 +1573,7 @@ private void letStructBinding(final InputInfo ii, final LinkedList<Clause> claus
     for(final Var var : vrs) {
       final Expr expr = switch(binding.endCp) {
         case ']' -> Function._ARRAY_GET.get(var.info, seqRef, Itr.get(++i));
-        case '}' -> Function._MAP_GET.get(var.info, seqRef, Str.get(var.name.local()));
+        case '}' -> new Lookup(var.info, seqRef, Str.get(var.name.local()));
         default -> (++i < vrs.size() ? Function.ITEMS_AT : Function.SUBSEQUENCE).
           get(var.info, seqRef, Itr.get(i));
       };

basex-core/src/main/java/org/basex/query/expr/Lookup.java

@@ -39,7 +39,7 @@ public Lookup(final InputInfo info, final Expr... expr) {
   public Expr optimize(final CompileContext cc) throws QueryException {
     exprs[1] = exprs[1].simplifyFor(Simplify.DATA, cc);
 
-    final Expr inputs = exprs[0];
+    final Expr inputs = exprs[0], keys = exprs[1];
     final long is = inputs.size();
     if(is == 0) return cc.replaceWith(this, inputs);
 
@@ -48,11 +48,13 @@ public Expr optimize(final CompileContext cc) throws QueryException {
     final boolean map = tp instanceof MapType, array = tp instanceof ArrayType;
     if(!(map || array)) return this;
 
+    // pre-evaluate a single-key lookup
+    if(is == 1 && inputs instanceof Value && keys instanceof Item) return cc.preEval(this);
+
     final Expr expr = opt(cc);
     if(expr != this) return cc.replaceWith(this, expr);
 
     // derive type from input expression
-    final Expr keys = exprs[1];
     final SeqType kt = keys.seqType();
     final SeqType st = map ? ((MapType) tp).valueType() : ((ArrayType) tp).valueType();
     Occ occ = st.occ;
@@ -80,12 +82,14 @@ private Expr opt(final CompileContext cc) throws QueryException {
     if(ks == 0) return keys;
 
     final Type it = input.seqType().type;
-    if(it instanceof final RecordType rt && rt.strict() && keys != WILDCARD &&
-        !(keys instanceof final AStr str && ks == 1 && rt.fields().contains(str.string(info)))) {
-      return this;
-    }
     final boolean map = it instanceof MapType, array = it instanceof ArrayType;
     if(map || array) {
+      // keep the lookup if a runtime value could be a strict record that lacks a requested key
+      if(keys != WILDCARD && it instanceof final MapType mt && (mt instanceof final RecordType rt
+          ? rt.strict() && !(ks == 1 && keys instanceof final AStr str &&
+              rt.fields().contains(str.string(info)))
+          : mt.keyType().intersect(BasicType.STRING) != null)) return this;
+
       /* REWRITE LOOKUP:
        *  MAP?*     → map:items(MAP)
        *  ARRAY?*   → array:items(MAP)

basex-core/src/main/java/org/basex/query/value/type/RecordType.java

@@ -23,9 +23,7 @@ public final class RecordType extends MapType {
   /** Maximum number of entries in generated records. */
   public static final int MAX_GENERATED_SIZE = 32;
 
-  /** Sealed flag: a sealed record type carries a runtime type annotation and constrains
-   * field access (lookup of an undeclared field raises a type error). Inferred record types
-   * (e.g. from map constructors) are not sealed and behave like ordinary maps. */
+  /** Sealed flag (runtime type annotation, constrains field access). */
   private final boolean sealed;
   /** Record fields. */
   private final TokenObjectMap<RecordField> fields;

basex-core/src/test/java/org/basex/query/expr/LookupTest.java

@@ -16,6 +16,7 @@ public final class LookupTest extends SandboxTest {
   /** Test. */
   @Test public void map() {
     query("{ 'a': 'b' } ? a", "b");
+    query("{ 'a': 'b' } ? c", "");
     query("({ 'a': 'b' }, { 'c': 'd' }) ? a", "b");
     query("{ 'a': 'b', 'c': 'd' } ? ('a', 'c')", "b\nd");
     query("({ 'a': 'b' }, { 'c': 'd' }) ? ('a', 'c')", "b\nd");
@@ -84,8 +85,26 @@ public final class LookupTest extends SandboxTest {
     query("({ 'k': 7 }, { 'k': 8 }) ! self::jnode()?k", "7\n8");
   }
 
+  /** Rewrite lookups to map:get/array:get unless this could suppress a strict-record error. */
+  @Test public void rewrite() {
+    check("({ 'a': <x/> }, { 'b': <y/> })?a", "<x/>", exists(Lookup.class), empty(_MAP_GET));
+    check("declare record local:r(a, b); local:r(<x/>, <y/>)?('a', 'b')", "<x/>\n<y/>",
+        exists(Lookup.class));
+    check("[ <x/>, <y/> ]?(1, 2)", "<x/>\n<y/>", exists(Lookup.class));
+
+    check("({ 'a': <x/> })?a", "<x/>", exists(RecordGet.class), empty(Lookup.class));
+    check("({ 'a': <x/> })?b", "", empty(Lookup.class));
+    check("({ 1: <x/> })?1", "<x/>", exists(_MAP_GET), empty(Lookup.class));
+    check("({ 'a': <x/> })?*", "<x/>", exists(_MAP_ITEMS), empty(Lookup.class));
+    check("[ <x/> ]?1", "<x/>", exists(_ARRAY_GET), empty(Lookup.class));
+    check("[ <x/> ]?*", "<x/>", exists(_ARRAY_ITEMS), empty(Lookup.class));
+  }
+
   /** Test. */
   @Test public void error() {
     error("1?a", LOOKUP_X);
+    error("declare record local:r(a, b); local:r(1, 2)?c", RECORDFIELD_X_X);
+    error("declare record local:r(a, b); (local:r(1, 2), { 'c': 3 })?c", RECORDFIELD_X_X);
+    error("declare record local:r(a, b); local:r(<x/>, <y/>)?1", RECORDFIELD_X_X);
   }
 }

basex-core/src/test/java/org/basex/query/expr/XQuery4Test.java

@@ -876,6 +876,13 @@ public final class XQuery4Test extends SandboxTest {
     query("let ${$a, $b, $c} := " + value + " return [ $a, $b, $c ]", "[1,2,3]");
     query("let ${$a, $b, $c, $d} := " + value + " return [ $a, $b, $c, $d ]", "[1,2,3,()]");
 
+    query("declare record local:r(a as xs:integer, b as xs:integer); "
+        + "let ${ $a, $b } := local:r(1, 2) return $a + $b", 3);
+    error("declare record local:r(a as xs:integer, b as xs:integer); "
+        + "let ${ $c } := local:r(1, 2) return $c", RECORDFIELD_X_X);
+    query("let $m as map(xs:string, xs:integer) := map:merge(('a', 'b') ! map:entry(., 1)) "
+        + "let ${ $z } := $m return empty($z)", true);
+
     // GH-2452
     query("""
       let $($a, $b) := (1 to 6) ! string()