(groovy) branch master updated: GROOVY-11807: MapWithDefault can break type safety of key set

[pa...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

paulk-asert pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/groovy.git


The following commit(s) were added to refs/heads/master by this push:
     new c1f1e5e957 GROOVY-11807: MapWithDefault can break type safety of key set
c1f1e5e957 is described below

commit c1f1e5e957da602b78db3d5f1f1ba4688a492ece
Author: Paul King <pa...@asert.com.au>
AuthorDate: Mon Jun 29 10:39:21 2026 +1000

    GROOVY-11807: MapWithDefault can break type safety of key set
---
 .../groovy/runtime/DefaultGroovyMethods.java       | 56 ++++++++++++++
 src/test/groovy/bugs/Groovy11807.groovy            | 90 ++++++++++++++++++++++
 2 files changed, 146 insertions(+)

diff --git a/src/main/java/org/codehaus/groovy/runtime/DefaultGroovyMethods.java b/src/main/java/org/codehaus/groovy/runtime/DefaultGroovyMethods.java
index 49b8f2ffc9..1bdc413303 100644
--- a/src/main/java/org/codehaus/groovy/runtime/DefaultGroovyMethods.java
+++ b/src/main/java/org/codehaus/groovy/runtime/DefaultGroovyMethods.java
@@ -19155,6 +19155,62 @@ public class DefaultGroovyMethods extends DefaultGroovyMethodsSupport {
         return MapWithDefault.newInstance(self, autoGrow, autoShrink, init);
     }
 
+    /**
+     * Decorates the given Map with a default value supplied by a closure, as per
+     * {@link #withDefault(Map, Closure)}, but the returned map additionally enforces its
+     * key and value types at runtime. Looking up (and so auto-growing for) a key that is
+     * not an instance of {@code keyType} throws {@link ClassCastException} at the point of
+     * misuse, rather than silently inserting a wrong-typed key that only surfaces later
+     * (for example when reading {@code keySet()}). The check is provided by decorating an
+     * {@link #asChecked(Map, Class, Class) asChecked} view, so direct mutation such as
+     * {@code map[key] = value} is guarded too.
+     * <pre class="language-groovy">
+     * def m = [:].withDefault(Number, String){ 'n/a' }
+     * assert m[1] == 'n/a'       // a compatible key (and String default) grows the map
+     * // m['x']                  // would throw ClassCastException (incompatible key)
+     * // m[2] = 99               // would throw ClassCastException (incompatible value)
+     * </pre>
+     * The {@code keyType} and {@code valueType} arguments are candidates to be supplied
+     * automatically from the map's static type under static compilation (GROOVY-12115);
+     * until then they are passed explicitly and this variant also works in dynamic code.
+     *
+     * @param self a Map
+     * @param keyType the required runtime key type
+     * @param valueType the required runtime value type
+     * @param init a Closure which when passed a {@code key} returns the default value
+     * @return a wrapped Map that enforces key/value types and returns a default value for missing keys
+     * @see #withDefault(Map, Closure)
+     * @see #asChecked(Map, Class, Class)
+     * @since 6.0.0
+     */
+    @Incubating
+    public static <K, V> Map<K, V> withDefault(Map<K, V> self, /* @ClassTag GROOVY-12115 */ Class<K> keyType, /* @ClassTag */ Class<V> valueType, @ClosureParams(FirstParam.FirstGenericType.class) Closure<V> init) {
+        return withDefault(asChecked(self, keyType, valueType), init);
+    }
+
+    /**
+     * Key-checked variant of {@link #withDefault(Map, Class, Class, Closure)} for the common
+     * case (such as a {@code Map<Number, ?>}) where only the key type needs enforcing; values
+     * are left unchecked.
+     * <pre class="language-groovy">
+     * def m = [:].withDefault(Number){ null }
+     * assert m[1] == null
+     * // m['x']                  // would throw ClassCastException (incompatible key)
+     * </pre>
+     *
+     * @param self a Map
+     * @param keyType the required runtime key type
+     * @param init a Closure which when passed a {@code key} returns the default value
+     * @return a wrapped Map that enforces the key type and returns a default value for missing keys
+     * @see #withDefault(Map, Class, Class, Closure)
+     * @since 6.0.0
+     */
+    @Incubating
+    @SuppressWarnings("unchecked")
+    public static <K, V> Map<K, V> withDefault(Map<K, V> self, /* @ClassTag GROOVY-12115 */ Class<K> keyType, @ClosureParams(FirstParam.FirstGenericType.class) Closure<V> init) {
+        return withDefault(self, keyType, (Class<V>) (Class<?>) Object.class, init);
+    }
+
     /**
      * An alias for <code>withLazyDefault</code> which decorates a list allowing
      * it to grow when called with index values outside the normal list bounds.
diff --git a/src/test/groovy/bugs/Groovy11807.groovy b/src/test/groovy/bugs/Groovy11807.groovy
new file mode 100644
index 0000000000..a0bb6d307f
--- /dev/null
+++ b/src/test/groovy/bugs/Groovy11807.groovy
@@ -0,0 +1,90 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you under the Apache License, Version 2.0 (the
+ *  "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied.  See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package bugs
+
+import org.junit.jupiter.api.Test
+
+import static groovy.test.GroovyAssert.assertScript
+
+/**
+ * The plain {@code withDefault} decorator grows a map for any looked-up key, which can
+ * silently insert a key incompatible with the map's declared key type — only surfacing
+ * later (e.g. when reading {@code keySet()}). The key-checked {@code withDefault(Map, Class, Closure)}
+ * overload (built over {@code asChecked}) rejects an incompatible key at the point of misuse
+ * (GROOVY-11807). The transparent, auto-supplied-{@code Class} form is tracked as GROOVY-12115.
+ */
+final class Groovy11807 {
+
+    @Test
+    void testKeyCheckedWithDefaultRejectsIncompatibleKey() {
+        assertScript '''
+            Map<Number,?> map = [:].withDefault(Number){ null }
+            assert map[1] == null                  // a compatible key grows the map
+            assert map.get(2) == null
+            def err = groovy.test.GroovyAssert.shouldFail(ClassCastException) { map.get('x') }
+            assert err.message.contains('Number')
+            assert map.keySet().every { it instanceof Number }
+            Number k = map.keySet()[0]             // the original repro: no longer a runtime cast failure
+            assert k == 1
+        '''
+    }
+
+    @Test
+    void testKeyCheckedWithDefaultGuardsDirectPut() {
+        assertScript '''
+            def map = [:].withDefault(Number){ 0 }
+            map[1] = 10
+            groovy.test.GroovyAssert.shouldFail(ClassCastException) { map['x'] = 1 }
+            assert map.keySet().every { it instanceof Number }
+        '''
+    }
+
+    @Test
+    void testKeyAndValueCheckedWithDefault() {
+        assertScript '''
+            def map = [:].withDefault(Number, String){ 'def' }
+            assert map[1] == 'def'                                              // grows with compatible key/value
+            groovy.test.GroovyAssert.shouldFail(ClassCastException) { map.get('x') }  // incompatible key
+            groovy.test.GroovyAssert.shouldFail(ClassCastException) { map[2] = 99 }   // incompatible value
+        '''
+    }
+
+    @Test
+    void testPlainWithDefaultRemainsLenient() {
+        assertScript '''
+            def map = [:].withDefault{ null }
+            map.get('x')                           // unchanged behaviour: silently grows, no exception
+            assert map.containsKey('x')
+        '''
+    }
+
+    @Test
+    void testKeyCheckedWithDefaultUnderCompileStatic() {
+        assertScript '''
+            @groovy.transform.CompileStatic
+            String check() {
+                Map<Number,?> map = [:].withDefault(Number){ null }
+                assert map[1] == null
+                groovy.test.GroovyAssert.shouldFail(ClassCastException) { map.get('x') }
+                'ok'
+            }
+            assert check() == 'ok'
+        '''
+    }
+}