core: Move io.grpc to grpc-api

io.grpc has fewer dependencies than io.grpc.internal. Moving it to a
separate artifact lets users use the API without bringing in the deps.
If the library has an optional dependency on grpc, that can be quite
convenient.

We now version-pin both grpc-api and grpc-core, since both contain
internal APIs.

I had to change a few tests in grpc-api to avoid FakeClock. Moving
FakeClock to grpc-api was difficult because it uses
io.grpc.internal.TimeProvider, which can't be moved since it is a
production class. Having grpc-api's tests depend on grpc-core's test
classes would be weird and cause a circular dependincy. Having
grpc-api's tests depend on grpc-core is likely possible, but weird and
fairly unnecessary at this point. So instead I rewrote the tests to
avoid FakeClock.

Fixes #1447

BUILD.bazel

@@ -29,7 +29,7 @@ java_library(
     name = "java_grpc_library_deps__do_not_reference",
     visibility = ["//visibility:public"],
     exports = [
-        "//core",
+        "//api",
         "//protobuf",
         "//stub",
         "//stub:javax_annotation",
@@ -43,7 +43,7 @@ java_library(
     name = "java_lite_grpc_library_deps__do_not_reference",
     visibility = ["//visibility:public"],
     exports = [
-        "//core",
+        "//api",
         "//protobuf-lite",
         "//stub",
         "//stub:javax_annotation",

all/build.gradle

@@ -11,6 +11,7 @@ buildscript {
 }
 
 def subprojects = [
+    project(':grpc-api'),
     project(':grpc-auth'),
     project(':grpc-core'),
     project(':grpc-context'),

alts/BUILD.bazel

@@ -8,7 +8,7 @@ java_library(
     deps = [
         ":handshaker_java_grpc",
         ":handshaker_java_proto",
-        "//core",
+        "//api",
         "//core:internal",
         "//netty",
         "//stub",
@@ -35,8 +35,8 @@ java_library(
     deps = [
         ":alts_internal",
         ":handshaker_java_grpc",
+        "//api",
         "//auth",
-        "//core",
         "//core:internal",
         "//netty",
         "@com_google_auth_google_auth_library_oauth2_http//jar",

api/BUILD.bazel

@@ -0,0 +1,14 @@
+java_library(
+    name = "api",
+    srcs = glob([
+        "src/main/java/**/*.java",
+    ]),
+    visibility = ["//visibility:public"],
+    deps = [
+        "//context",
+        "@com_google_code_findbugs_jsr305//jar",
+        "@com_google_guava_failureaccess//jar",  # future transitive dep of Guava. See #5214
+        "@com_google_guava_guava//jar",
+        "@com_google_j2objc_j2objc_annotations//jar",
+    ],
+)

api/build.gradle

@@ -0,0 +1,32 @@
+description = 'gRPC: API'
+
+dependencies {
+    compile project(':grpc-context'),
+            libraries.errorprone,
+            libraries.jsr305,
+            libraries.animalsniffer_annotations
+    compile (libraries.guava) {
+        // prefer 2.3.2 from libraries instead of 2.1.3
+        exclude group: 'com.google.errorprone', module: 'error_prone_annotations'
+        // prefer 3.0.2 from libraries instead of 3.0.1
+        exclude group: 'com.google.code.findbugs', module: 'jsr305'
+        // prefer 1.17 from libraries instead of 1.14
+        exclude group: 'org.codehaus.mojo', module: 'animal-sniffer-annotations'
+    }
+
+    testCompile project(':grpc-context').sourceSets.test.output,
+            project(':grpc-testing'),
+            project(':grpc-grpclb'),
+            libraries.guava_testlib
+
+    jmh project(':grpc-core')
+
+    signature "org.codehaus.mojo.signature:java17:1.0@signature"
+    signature "net.sf.androidscents.signature:android-api-level-14:4.0_r4@signature"
+}
+
+javadoc {
+    // We want io.grpc.Internal, but not io.grpc.Internal*
+    exclude 'io/grpc/Internal?*.java'
+    exclude 'io/grpc/internal/**'
+}

api/src/test/java/io/grpc/ContextsTest.java

@@ -28,11 +28,13 @@ import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
-import io.grpc.internal.FakeClock;
+import com.google.common.util.concurrent.testing.TestingExecutors;
 import io.grpc.internal.NoopServerCall;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import org.junit.Test;
@@ -213,11 +215,29 @@ public class ContextsTest {
 
   @Test
   public void statusFromCancelled_TimeoutExceptionShouldMapToDeadlineExceeded() {
-    FakeClock fakeClock = new FakeClock();
+    final long expectedDelay = 100;
+    final TimeUnit expectedUnit = TimeUnit.SECONDS;
+    class MockScheduledExecutorService extends ForwardingScheduledExecutorService {
+      private ScheduledExecutorService delegate = TestingExecutors.noOpScheduledExecutor();
+      Runnable command;
+
+      @Override public ScheduledExecutorService delegate() {
+        return delegate;
+      }
+
+      @Override public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
+        if (delay > unit.convert(expectedDelay, expectedUnit)) {
+          fail("Delay larger than expected: " + delay + " " + unit);
+        }
+        this.command = command;
+        return super.schedule(command, delay, unit);
+      }
+    }
+
+    MockScheduledExecutorService executorService = new MockScheduledExecutorService();
     Context.CancellableContext cancellableContext = Context.current()
-        .withDeadlineAfter(100, TimeUnit.NANOSECONDS, fakeClock.getScheduledExecutorService());
-    fakeClock.forwardTime(System.nanoTime(), TimeUnit.NANOSECONDS);
-    fakeClock.forwardNanos(100);
+        .withDeadlineAfter(expectedDelay, expectedUnit, executorService);
+    executorService.command.run();
 
     assertTrue(cancellableContext.isCancelled());
     assertThat(cancellableContext.cancellationCause(), instanceOf(TimeoutException.class));