Apply path fences to the default lookups of a fenced interpolator

src/main/java/org/apache/commons/text/lookup/InterpolatorStringLookup.java

@@ -69,10 +69,23 @@ final class InterpolatorStringLookup extends AbstractStringLookup {
      */
     InterpolatorStringLookup(final Map<String, StringLookup> stringLookupMap, final StringLookup defaultStringLookup,
             final boolean addDefaultLookups) {
+        this(stringLookupMap, defaultStringLookup, addDefaultLookups, StringLookupFactory.INSTANCE);
+    }
+
+    /**
+     * Constructs a fully customized instance.
+     *
+     * @param stringLookupMap The map of string lookups.
+     * @param defaultStringLookup The default string lookup.
+     * @param addDefaultLookups whether the default lookups should be used.
+     * @param factory The factory providing the default lookups, and their Path fences.
+     */
+    InterpolatorStringLookup(final Map<String, StringLookup> stringLookupMap, final StringLookup defaultStringLookup,
+            final boolean addDefaultLookups, final StringLookupFactory factory) {
         this.defaultStringLookup = defaultStringLookup;
         this.stringLookupMap = stringLookupMap.entrySet().stream().collect(Collectors.toMap(e -> StringLookupFactory.toKey(e.getKey()), Entry::getValue));
         if (addDefaultLookups) {
-            StringLookupFactory.INSTANCE.addDefaultStringLookups(this.stringLookupMap);
+            factory.addDefaultStringLookups(this.stringLookupMap);
         }
     }
 

src/main/java/org/apache/commons/text/lookup/StringLookupFactory.java

@@ -672,6 +672,12 @@ private StringLookupFactory(final Path[] fences) {
     public void addDefaultStringLookups(final Map<String, StringLookup> stringLookupMap) {
         if (stringLookupMap != null) {
             stringLookupMap.putAll(DefaultStringLookupsHolder.INSTANCE.getDefaultStringLookups());
+            if (fences != null) {
+                // The defaults are unfenced singletons, replace them with lookups guarded by our fences.
+                stringLookupMap.replace(toKey(KEY_FILE), DefaultStringLookup.FILE.getStringLookup(), fileStringLookup(fences));
+                stringLookupMap.replace(toKey(KEY_PROPERTIES), DefaultStringLookup.PROPERTIES.getStringLookup(), propertiesStringLookup(fences));
+                stringLookupMap.replace(toKey(KEY_XML), DefaultStringLookup.XML.getStringLookup(), xmlStringLookup(Collections.emptyMap(), fences));
+            }
         }
     }
 
@@ -1031,7 +1037,7 @@ public <R> StringLookup functionStringLookup(final Function<String, R> function)
      * @return The default {@link InterpolatorStringLookup}.
      */
     public StringLookup interpolatorStringLookup() {
-        return InterpolatorStringLookup.INSTANCE;
+        return fences != null ? interpolatorStringLookup(Collections.emptyMap(), mapStringLookup(null), true) : InterpolatorStringLookup.INSTANCE;
     }
 
     /**
@@ -1048,7 +1054,7 @@ public StringLookup interpolatorStringLookup() {
      */
     public StringLookup interpolatorStringLookup(final Map<String, StringLookup> stringLookupMap, final StringLookup defaultStringLookup,
             final boolean addDefaultLookups) {
-        return new InterpolatorStringLookup(stringLookupMap, defaultStringLookup, addDefaultLookups);
+        return new InterpolatorStringLookup(stringLookupMap, defaultStringLookup, addDefaultLookups, this);
     }
 
     /**
@@ -1060,7 +1066,7 @@ public StringLookup interpolatorStringLookup(final Map<String, StringLookup> str
      * @return A new InterpolatorStringLookup.
      */
     public <V> StringLookup interpolatorStringLookup(final Map<String, V> map) {
-        return new InterpolatorStringLookup(map);
+        return interpolatorStringLookup(mapStringLookup(map));
     }
 
     /**
@@ -1071,7 +1077,7 @@ public <V> StringLookup interpolatorStringLookup(final Map<String, V> map) {
      * @return A new InterpolatorStringLookup.
      */
     public StringLookup interpolatorStringLookup(final StringLookup defaultStringLookup) {
-        return new InterpolatorStringLookup(defaultStringLookup);
+        return interpolatorStringLookup(Collections.emptyMap(), defaultStringLookup, true);
     }
 
     /**

src/test/java/org/apache/commons/text/lookup/StringLookupFactoryTest.java

@@ -106,6 +106,26 @@ void testAddDefaultStringLookupsNull() {
         StringLookupFactory.INSTANCE.addDefaultStringLookups(null);
     }
 
+    @Test
+    void testFencedInterpolatorStringLookup() {
+        final StringLookupFactory stringLookupFactory = StringLookupFactory.builder().setFences(XmlStringLookupTest.FENCE_ROOT).get();
+        final String fileKey = "file:UTF-8:" + XmlStringLookupTest.DOC_DIR + "document.properties";
+        final String propertiesKey = "properties:" + XmlStringLookupTest.DOC_DIR + "document.properties::mykey";
+        final String xmlKey = "xml:" + XmlStringLookupTest.DOC_DIR + "document.xml:/root/path/to/node";
+        // Unfenced, the documents outside the fence resolve.
+        assertEquals("Hello World!", StringLookupFactory.INSTANCE.interpolatorStringLookup().apply(propertiesKey));
+        assertEquals("Hello World!", StringLookupFactory.INSTANCE.interpolatorStringLookup().apply(xmlKey));
+        // Fenced, the default lookups of every interpolator must reject them.
+        for (final StringLookup stringLookup : new StringLookup[] { stringLookupFactory.interpolatorStringLookup(),
+                stringLookupFactory.interpolatorStringLookup(Collections.emptyMap()),
+                stringLookupFactory.interpolatorStringLookup(StringLookupFactory.INSTANCE.nullStringLookup()),
+                stringLookupFactory.interpolatorStringLookup(Collections.emptyMap(), null, true) }) {
+            assertThrows(IllegalArgumentException.class, () -> stringLookup.apply(fileKey));
+            assertThrows(IllegalArgumentException.class, () -> stringLookup.apply(propertiesKey));
+            assertThrows(IllegalArgumentException.class, () -> stringLookup.apply(xmlKey));
+        }
+    }
+
     @Test
     void testClear() {
         // this will clear out the global cache in ConstantStringLookup