Test function result caching (#399)

* Build some tests for function result caching.
* Adjusted focus handling to properly honor focus independence.

Author: david-waltermire

core/src/main/java/gov/nist/secauto/metaschema/core/metapath/function/impl/AbstractFunction.java

@@ -219,8 +219,11 @@ protected static ISequence<?> convertSequence(
     return ISequence.of(stream);
   }
 
+  @Nullable
   private IItem getContextItem(@NonNull ISequence<?> focus) {
-    IItem contextItem = focus.getFirstItem(true);
+    IItem contextItem = isFocusDependent()
+        ? focus.getFirstItem(true)
+        : null;
     if (isFocusDependent() && contextItem == null) {
       throw new DynamicMetapathException(DynamicMetapathException.DYNAMIC_CONTEXT_ABSENT, "The context is empty");
     }

core/src/test/java/gov/nist/secauto/metaschema/core/metapath/function/DefaultFunctionTest.java

@@ -0,0 +1,72 @@
+/*
+ * SPDX-FileCopyrightText: none
+ * SPDX-License-Identifier: CC0-1.0
+ */
+
+package gov.nist.secauto.metaschema.core.metapath.function;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+import gov.nist.secauto.metaschema.core.metapath.DynamicContext;
+import gov.nist.secauto.metaschema.core.metapath.StaticContext;
+import gov.nist.secauto.metaschema.core.metapath.item.ISequence;
+import gov.nist.secauto.metaschema.core.metapath.item.atomic.IBooleanItem;
+import gov.nist.secauto.metaschema.core.util.CollectionUtil;
+
+import org.junit.jupiter.api.Test;
+
+class DefaultFunctionTest {
+
+  /**
+   * Ensure that the same call to the fn:boolean function produces the exact same
+   * result instances.
+   */
+  @Test
+  void testSameResultCurrentDateTime() {
+    StaticContext staticContext = StaticContext.builder()
+        .build();
+
+    IFunction function = staticContext.lookupFunction("current-dateTime", 0);
+    assertNotNull(function);
+
+    DynamicContext dynamicContext = new DynamicContext(staticContext);
+
+    ISequence<?> result1 = function.execute(
+        CollectionUtil.emptyList(),
+        dynamicContext,
+        ISequence.empty());
+    ISequence<?> result2 = function.execute(
+        CollectionUtil.emptyList(),
+        dynamicContext,
+        ISequence.empty());
+
+    assertSame(result1, result2);
+  }
+
+  /**
+   * Ensure that the same call to the fn:boolean function with the same argument
+   * produces the exact same result instances.
+   */
+  @Test
+  void testSameResultBoolean() {
+    StaticContext staticContext = StaticContext.builder()
+        .build();
+
+    IFunction function = staticContext.lookupFunction("boolean", 1);
+    assertNotNull(function);
+
+    DynamicContext dynamicContext = new DynamicContext(staticContext);
+
+    ISequence<?> result1 = function.execute(
+        CollectionUtil.singletonList(ISequence.of(IBooleanItem.valueOf(true))),
+        dynamicContext,
+        ISequence.empty());
+    ISequence<?> result2 = function.execute(
+        CollectionUtil.singletonList(ISequence.of(IBooleanItem.valueOf(true))),
+        dynamicContext,
+        ISequence.empty());
+
+    assertSame(result1, result2);
+  }
+}

databind/src/test/java/gov/nist/secauto/metaschema/databind/FnDocTest.java

@@ -0,0 +1,54 @@
+/*
+ * SPDX-FileCopyrightText: none
+ * SPDX-License-Identifier: CC0-1.0
+ */
+
+package gov.nist.secauto.metaschema.databind;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+import gov.nist.secauto.metaschema.core.metapath.DynamicContext;
+import gov.nist.secauto.metaschema.core.metapath.StaticContext;
+import gov.nist.secauto.metaschema.core.metapath.function.IFunction;
+import gov.nist.secauto.metaschema.core.metapath.item.ISequence;
+import gov.nist.secauto.metaschema.core.metapath.item.atomic.IStringItem;
+import gov.nist.secauto.metaschema.core.util.CollectionUtil;
+
+import org.junit.jupiter.api.Test;
+
+import java.nio.file.Paths;
+
+class FnDocTest {
+
+  /**
+   * Ensure that the same document loaded twice produces the exact same node
+   * instances.
+   */
+  @Test
+  void testSameNode() {
+    IBindingContext bindingContext = IBindingContext.newInstance();
+
+    StaticContext staticContext = StaticContext.builder()
+        .baseUri(Paths.get(".").toUri())
+        .build();
+    DynamicContext dynamicContext = new DynamicContext(staticContext);
+    dynamicContext.setDocumentLoader(bindingContext.newBoundLoader());
+
+    IFunction function = staticContext.lookupFunction("doc", 1);
+    assertNotNull(function);
+
+    ISequence<?> result1 = function.execute(
+        CollectionUtil
+            .singletonList(ISequence.of(IStringItem.valueOf("src/test/resources/metaschema/simple/metaschema.xml"))),
+        dynamicContext,
+        ISequence.empty());
+
+    ISequence<?> result2 = function.execute(
+        CollectionUtil
+            .singletonList(ISequence.of(IStringItem.valueOf("src/test/resources/metaschema/simple/metaschema.xml"))),
+        dynamicContext,
+        ISequence.empty());
+    assertSame(result1, result2);
+  }
+}