core: add accessor for bare method name in MethodDescriptor (#7339)

Added getBareMethodName and extractBareMethodName for accessing the unqualified method name.

api/src/main/java/io/grpc/MethodDescriptor.java

@@ -262,6 +262,17 @@ public final class MethodDescriptor<ReqT, RespT> {
     return serviceName;
   }
 
+  /**
+   * A convenience method for {@code extractBareMethodName(getFullMethodName())}.
+   *
+   * @since 1.32.0
+   */
+  @Nullable
+  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/5635")
+  public String getBareMethodName() {
+    return extractBareMethodName(fullMethodName);
+  }
+
   /**
    * Parse a response payload from the given {@link InputStream}.
    *
@@ -398,6 +409,22 @@ public final class MethodDescriptor<ReqT, RespT> {
     return fullMethodName.substring(0, index);
   }
 
+  /**
+   * Extract the method name out of a fully qualified method name. May return {@code null}
+   * if the input is malformed, but you cannot rely on it for the validity of the input.
+   *
+   * @since 1.32.0
+   */
+  @Nullable
+  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/5635")
+  public static String extractBareMethodName(String fullMethodName) {
+    int index = checkNotNull(fullMethodName, "fullMethodName").lastIndexOf('/');
+    if (index == -1) {
+      return null;
+    }
+    return fullMethodName.substring(index + 1);
+  }
+
   /**
    * Creates a new builder for a {@link MethodDescriptor}.
    *

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

@@ -177,6 +177,39 @@ public class MethodDescriptorTest {
     assertNull(md.getServiceName());
   }
 
+  @Test
+  public void getBareMethodName_extractsMethod() {
+    Marshaller<Void> marshaller = TestMethodDescriptors.voidMarshaller();
+    MethodDescriptor<?, ?> md = MethodDescriptor.newBuilder(marshaller, marshaller)
+        .setType(MethodType.UNARY)
+        .setFullMethodName("foo/bar")
+        .build();
+
+    assertEquals("bar", md.getBareMethodName());
+  }
+
+  @Test
+  public void getBareMethodName_returnsNull() {
+    Marshaller<Void> marshaller = TestMethodDescriptors.voidMarshaller();
+    MethodDescriptor<?, ?> md = MethodDescriptor.newBuilder(marshaller, marshaller)
+        .setType(MethodType.UNARY)
+        .setFullMethodName("foo-bar")
+        .build();
+
+    assertNull(md.getBareMethodName());
+  }
+
+  @Test
+  public void getBareMethodName_returnsEmptyStringWithMethodMissing() {
+    Marshaller<Void> marshaller = TestMethodDescriptors.voidMarshaller();
+    MethodDescriptor<?, ?> md = MethodDescriptor.newBuilder(marshaller, marshaller)
+        .setType(MethodType.UNARY)
+        .setFullMethodName("foo/")
+        .build();
+
+    assertTrue(md.getBareMethodName().isEmpty());
+  }
+
   @Test
   public void toBuilderTest() {
     MethodDescriptor<String, String> md1 = MethodDescriptor.<String, String>newBuilder()