core: add ability to create stackless status exceptions

4 files changed, 170 insertions, 0 deletions

diff --git a/core/src/main/java/io/grpc/StatusException.java b/core/src/main/java/io/grpc/StatusException.java
index f9416bf72..e89ac16dc 100644
--- a/core/src/main/java/io/grpc/StatusException.java
+++ b/core/src/main/java/io/grpc/StatusException.java
@@ -27,6 +27,7 @@ public class StatusException extends Exception {
   private static final long serialVersionUID = -660954903976144640L;
   private final Status status;
   private final Metadata trailers;
+  private final boolean fillInStackTrace;
 
   /**
    * Constructs an exception with both a status.  See also {@link Status#asException()}.
@@ -44,9 +45,25 @@ public class StatusException extends Exception {
    * @since 1.0.0
    */
   public StatusException(Status status, @Nullable Metadata trailers) {
+    this(status, trailers, /*fillInStackTrace=*/ true);
+  }
+
+  StatusException(Status status, @Nullable Metadata trailers, boolean fillInStackTrace) {
     super(Status.formatThrowableMessage(status), status.getCause());
     this.status = status;
     this.trailers = trailers;
+    this.fillInStackTrace = fillInStackTrace;
+    fillInStackTrace();
+  }
+
+  @Override
+  public synchronized Throwable fillInStackTrace() {
+    // Let's observe final variables in two states!  This works because Throwable will invoke this
+    // method before fillInStackTrace is set, thus doing nothing.  After the constructor has set
+    // fillInStackTrace, this method will properly fill it in.  Additionally, sub classes may call
+    // this normally, because fillInStackTrace will either be set, or this method will be
+    // overriden.
+    return fillInStackTrace ? super.fillInStackTrace() : this;
   }
 
   /**
diff --git a/core/src/main/java/io/grpc/StatusRuntimeException.java b/core/src/main/java/io/grpc/StatusRuntimeException.java
index d685464d4..27e2e6117 100644
--- a/core/src/main/java/io/grpc/StatusRuntimeException.java
+++ b/core/src/main/java/io/grpc/StatusRuntimeException.java
@@ -29,6 +29,8 @@ public class StatusRuntimeException extends RuntimeException {
   private final Status status;
   private final Metadata trailers;
 
+  private final boolean fillInStackTrace;
+
   /**
    * Constructs the exception with both a status.  See also {@link Status#asException()}.
    *
@@ -45,9 +47,25 @@ public class StatusRuntimeException extends RuntimeException {
    * @since 1.0.0
    */
   public StatusRuntimeException(Status status, @Nullable Metadata trailers) {
+    this(status, trailers, /*fillInStackTrace=*/ true);
+  }
+
+  StatusRuntimeException(Status status, @Nullable Metadata trailers, boolean fillInStackTrace) {
     super(Status.formatThrowableMessage(status), status.getCause());
     this.status = status;
     this.trailers = trailers;
+    this.fillInStackTrace = fillInStackTrace;
+    fillInStackTrace();
+  }
+
+  @Override
+  public synchronized Throwable fillInStackTrace() {
+    // Let's observe final variables in two states!  This works because Throwable will invoke this
+    // method before fillInStackTrace is set, thus doing nothing.  After the constructor has set
+    // fillInStackTrace, this method will properly fill it in.  Additionally, sub classes may call
+    // this normally, because fillInStackTrace will either be set, or this method will be
+    // overriden.
+    return fillInStackTrace ? super.fillInStackTrace() : this;
   }
 
   /**
diff --git a/core/src/test/java/io/grpc/StatusExceptionTest.java b/core/src/test/java/io/grpc/StatusExceptionTest.java
new file mode 100644
index 000000000..dd0d12dcc
--- /dev/null
+++ b/core/src/test/java/io/grpc/StatusExceptionTest.java
@@ -0,0 +1,67 @@
+/*
+ * Copyright 2018 The gRPC Authors
+ *
+ * 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 io.grpc;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/**
+ * Tests for {@link StatusException}.
+ */
+@RunWith(JUnit4.class)
+public class StatusExceptionTest {
+
+  @Test
+  public void internalCtorRemovesStack() {
+    StackTraceElement[] trace =
+        new StatusException(Status.CANCELLED, null, false) {}.getStackTrace();
+
+    assertThat(trace).isEmpty();
+  }
+
+  @Test
+  public void normalCtorKeepsStack() {
+    StackTraceElement[] trace =
+        new StatusException(Status.CANCELLED, null) {}.getStackTrace();
+
+    assertThat(trace).isNotEmpty();
+  }
+
+  @Test
+  public void extendPreservesStack() {
+    StackTraceElement[] trace = new StatusException(Status.CANCELLED) {}.getStackTrace();
+
+    assertThat(trace).isNotEmpty();
+  }
+
+  @Test
+  public void extendAndOverridePreservesStack() {
+    final StackTraceElement element = new StackTraceElement("a", "b", "c", 4);
+    StatusException exception = new StatusException(Status.CANCELLED, new Metadata()) {
+
+      @Override
+      public synchronized Throwable fillInStackTrace() {
+        setStackTrace(new StackTraceElement[]{element});
+        return this;
+      }
+    };
+    assertThat(exception.getStackTrace()).asList().containsExactly(element);
+  }
+}
diff --git a/core/src/test/java/io/grpc/StatusRuntimeExceptionTest.java b/core/src/test/java/io/grpc/StatusRuntimeExceptionTest.java
new file mode 100644
index 000000000..2c3bf7e9c
--- /dev/null
+++ b/core/src/test/java/io/grpc/StatusRuntimeExceptionTest.java
@@ -0,0 +1,68 @@
+/*
+ * Copyright 2018 The gRPC Authors
+ *
+ * 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 io.grpc;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/**
+ * Tests for {@link StatusRuntimeException}.
+ */
+@RunWith(JUnit4.class)
+public class StatusRuntimeExceptionTest {
+
+  @Test
+  public void internalCtorRemovesStack() {
+    StackTraceElement[] trace =
+        new StatusRuntimeException(Status.CANCELLED, null, false) {}.getStackTrace();
+
+    assertThat(trace).isEmpty();
+  }
+
+  @Test
+  public void normalCtorKeepsStack() {
+    StackTraceElement[] trace =
+        new StatusRuntimeException(Status.CANCELLED, null) {}.getStackTrace();
+
+    assertThat(trace).isNotEmpty();
+  }
+
+  @Test
+  public void extendPreservesStack() {
+    StackTraceElement[] trace = new StatusRuntimeException(Status.CANCELLED) {}.getStackTrace();
+
+    assertThat(trace).isNotEmpty();
+  }
+
+  @Test
+  public void extendAndOverridePreservesStack() {
+    final StackTraceElement element = new StackTraceElement("a", "b", "c", 4);
+    StatusRuntimeException exception =
+        new StatusRuntimeException(Status.CANCELLED, new Metadata()) {
+
+      @Override
+      public synchronized Throwable fillInStackTrace() {
+        setStackTrace(new StackTraceElement[]{element});
+        return this;
+      }
+    };
+    assertThat(exception.getStackTrace()).asList().containsExactly(element);
+  }
+}