Fix mutability bug in SkylarkList/SkylarkMap Java APIs

Previously, you could modify a frozen MutableList indirectly via its iterator(). This CL wraps the underlying list with a Collections.unmodifiableList when obtaining the iterator, and likewise for other methods that return views over Skylark data structures.

This also eliminates the SkylarkList#getContents method in favor of just using the SkylarkList object itself.

RELNOTES: None
PiperOrigin-RevId: 164402129

2 files changed, 130 insertions, 0 deletions

diff --git a/src/test/java/com/google/devtools/build/lib/syntax/SkylarkListTest.java b/src/test/java/com/google/devtools/build/lib/syntax/SkylarkListTest.java
index 161b91341d..df518ca67d 100644
--- a/src/test/java/com/google/devtools/build/lib/syntax/SkylarkListTest.java
+++ b/src/test/java/com/google/devtools/build/lib/syntax/SkylarkListTest.java
@@ -14,7 +14,10 @@
 package com.google.devtools.build.lib.syntax;
 
 import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.fail;
 
+import com.google.common.collect.ImmutableList;
+import com.google.devtools.build.lib.syntax.SkylarkList.MutableList;
 import com.google.devtools.build.lib.syntax.SkylarkList.Tuple;
 import com.google.devtools.build.lib.syntax.util.EvaluationTestCase;
 import org.junit.Test;
@@ -242,4 +245,42 @@ public class SkylarkListTest extends EvaluationTestCase {
     assertThat(eval("() == (1,)")).isEqualTo(false);
     assertThat(eval("(1) == (1,)")).isEqualTo(false);
   }
+
+  @Test
+  public void testMutatorsCheckMutability() throws Exception {
+    Mutability mutability = Mutability.create("test");
+    MutableList<Object> list = MutableList.copyOf(mutability, ImmutableList.of(1, 2, 3));
+    mutability.freeze();
+
+    try {
+      list.add(4, null, mutability);
+      fail("expected exception");
+    } catch (EvalException e) {
+      assertThat(e).hasMessage("trying to mutate a frozen object");
+    }
+    try {
+      list.add(0, 4, null, mutability);
+      fail("expected exception");
+    } catch (EvalException e) {
+      assertThat(e).hasMessage("trying to mutate a frozen object");
+    }
+    try {
+      list.addAll(ImmutableList.of(4, 5, 6), null, mutability);
+      fail("expected exception");
+    } catch (EvalException e) {
+      assertThat(e).hasMessage("trying to mutate a frozen object");
+    }
+    try {
+      list.remove(0, null, mutability);
+      fail("expected exception");
+    } catch (EvalException e) {
+      assertThat(e).hasMessage("trying to mutate a frozen object");
+    }
+    try {
+      list.set(0, 10, null, mutability);
+      fail("expected exception");
+    } catch (EvalException e) {
+      assertThat(e).hasMessage("trying to mutate a frozen object");
+    }
+  }
 }
diff --git a/src/test/java/com/google/devtools/build/lib/syntax/SkylarkMutableTest.java b/src/test/java/com/google/devtools/build/lib/syntax/SkylarkMutableTest.java
new file mode 100644
index 0000000000..5232f0446e
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/lib/syntax/SkylarkMutableTest.java
@@ -0,0 +1,89 @@
+// Copyright 2017 The Bazel Authors. All rights reserved.
+//
+// Licensed 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 com.google.devtools.build.lib.syntax;
+
+import static org.junit.Assert.fail;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.devtools.build.lib.syntax.SkylarkList.MutableList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map.Entry;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link SkylarkMutable}. */
+@RunWith(JUnit4.class)
+public final class SkylarkMutableTest {
+
+  @Test
+  public void testViewsCheckMutability() throws Exception {
+    Mutability mutability = Mutability.create("test");
+    MutableList<Object> list = MutableList.copyOf(mutability, ImmutableList.of(1, 2, 3));
+    SkylarkDict<Object, Object> dict = SkylarkDict.copyOf(mutability, ImmutableMap.of(1, 2, 3, 4));
+    mutability.freeze();
+
+    try {
+      Iterator<?> it = list.iterator();
+      it.next();
+      it.remove();
+      fail("expected exception");
+    } catch (UnsupportedOperationException expected) {
+    }
+    try {
+      Iterator<?> it = list.listIterator();
+      it.next();
+      it.remove();
+      fail("expected exception");
+    } catch (UnsupportedOperationException expected) {
+    }
+    try {
+      Iterator<?> it = list.listIterator(1);
+      it.next();
+      it.remove();
+      fail("expected exception");
+    } catch (UnsupportedOperationException expected) {
+    }
+    try {
+      List<Object> sublist = list.subList(1, 2);
+      sublist.set(0, 4);
+      fail("expected exception");
+    } catch (UnsupportedOperationException expected) {
+    }
+    try {
+      Iterator<Entry<Object, Object>> it = dict.entrySet().iterator();
+      Entry<Object, Object> entry = it.next();
+      entry.setValue(5);
+      fail("expected exception");
+    } catch (UnsupportedOperationException expected) {
+    }
+    try {
+      Iterator<Object> it = dict.keySet().iterator();
+      it.next();
+      it.remove();
+      fail("expected exception");
+    } catch (UnsupportedOperationException expected) {
+    }
+    try {
+      Iterator<Object> it = dict.values().iterator();
+      it.next();
+      it.remove();
+      fail("expected exception");
+    } catch (UnsupportedOperationException expected) {
+    }
+  }
+}