Add missing default function for match() (#587)

Author: songy23

core/src/main/java/io/opencensus/stats/Measure.java

@@ -37,7 +37,8 @@ public abstract class Measure {
    */
   public abstract <T> T match(
       Function<? super MeasureDouble, T> p0,
-      Function<? super MeasureLong, T> p1);
+      Function<? super MeasureLong, T> p1,
+      Function<? super Measure, T> defaultFunction);
 
   /**
    * Name of measure, as a {@code String}. Should be a ASCII string with a length no greater than
@@ -91,7 +92,10 @@ public static MeasureDouble create(String name, String description, String unit)
     }
 
     @Override
-    public <T> T match(Function<? super MeasureDouble, T> p0, Function<? super MeasureLong, T> p1) {
+    public <T> T match(
+        Function<? super MeasureDouble, T> p0,
+        Function<? super MeasureLong, T> p1,
+        Function<? super Measure, T> defaultFunction) {
       return p0.apply(this);
     }
 
@@ -127,7 +131,10 @@ public static MeasureLong create(String name, String description, String unit) {
     }
 
     @Override
-    public <T> T match(Function<? super MeasureDouble, T> p0, Function<? super MeasureLong, T> p1) {
+    public <T> T match(
+        Function<? super MeasureDouble, T> p0,
+        Function<? super MeasureLong, T> p1,
+        Function<? super Measure, T> defaultFunction) {
       return p1.apply(this);
     }
 

core/src/main/java/io/opencensus/stats/Measurement.java

@@ -30,7 +30,9 @@ public abstract class Measurement {
    * Applies the given match function to the underlying data type.
    */
   public abstract <T> T match(
-      Function<? super MeasurementDouble, T> p0, Function<? super MeasurementLong, T> p1);
+      Function<? super MeasurementDouble, T> p0,
+      Function<? super MeasurementLong, T> p1,
+      Function<? super Measurement, T> defaultFunction);
 
   /**
    * Extracts the measured {@link Measure}.
@@ -60,7 +62,9 @@ public static MeasurementDouble create(MeasureDouble measure, double value) {
 
     @Override
     public <T> T match(
-        Function<? super MeasurementDouble, T> p0, Function<? super MeasurementLong, T> p1) {
+        Function<? super MeasurementDouble, T> p0,
+        Function<? super MeasurementLong, T> p1,
+        Function<? super Measurement, T> defaultFunction) {
       return p0.apply(this);
     }
   }
@@ -84,7 +88,9 @@ public static MeasurementLong create(MeasureLong measure, long value) {
 
     @Override
     public <T> T match(
-        Function<? super MeasurementDouble, T> p0, Function<? super MeasurementLong, T> p1) {
+        Function<? super MeasurementDouble, T> p0,
+        Function<? super MeasurementLong, T> p1,
+        Function<? super Measurement, T> defaultFunction) {
       return p1.apply(this);
     }
   }

core/src/test/java/io/opencensus/stats/MeasureTest.java

@@ -18,8 +18,14 @@
 
 import static com.google.common.truth.Truth.assertThat;
 
+import com.google.common.collect.Lists;
 import com.google.common.testing.EqualsTester;
+import io.opencensus.common.Function;
+import io.opencensus.common.Functions;
+import io.opencensus.stats.Measure.MeasureDouble;
+import io.opencensus.stats.Measure.MeasureLong;
 import java.util.Arrays;
+import java.util.List;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
@@ -115,6 +121,32 @@ public void testMeasureLongEquals() {
         .testEquals();
   }
 
+  @Test
+  public void testMatch() {
+    List<Measure> measures = Arrays.asList(
+        MeasureDouble.create("measure1", "description", "1"),
+        MeasureLong.create("measure2", "description", "1"));
+    List<String> outputs = Lists.newArrayList();
+    for (Measure measure : measures) {
+      outputs.add(
+          measure.match(
+              new Function<MeasureDouble, String>() {
+                @Override
+                public String apply(MeasureDouble arg) {
+                  return "double";
+                }
+              },
+              new Function<MeasureLong, String>() {
+                @Override
+                public String apply(MeasureLong arg) {
+                  return "long";
+                }
+              },
+              Functions.<String>throwAssertionError()));
+    }
+    assertThat(outputs).containsExactly("double", "long").inOrder();
+  }
+
   @Test
   public void testMeasureDoubleIsNotEqualToMeasureLong() {
     assertThat(Measure.MeasureDouble.create("name", "description", "bit/s"))

core_impl/src/main/java/io/opencensus/implcore/stats/MeasureToViewMap.java

@@ -20,6 +20,7 @@
 import com.google.common.collect.Multimap;
 import io.opencensus.common.Clock;
 import io.opencensus.common.Function;
+import io.opencensus.common.Functions;
 import io.opencensus.common.Timestamp;
 import io.opencensus.stats.MeasureMap;
 import io.opencensus.stats.Measurement;
@@ -101,7 +102,8 @@ synchronized void record(TagContext tags, MeasureMap stats, Timestamp timestamp)
       for (MutableViewData view : views) {
         measurement.match(
             new RecordDoubleValueFunc(tags, view, timestamp),
-            new RecordLongValueFunc(tags, view, timestamp));
+            new RecordLongValueFunc(tags, view, timestamp),
+            Functions.<Void>throwAssertionError());
       }
     }
   }