Support ToString in RepeatedField and MapField.

This changes how we approach JSON formatting in general - instead of looking  at the field a value came from, we just look at the type of the value. It's possible this *could* be slightly inefficient, but if we start caring about JSON performance deeply, we'll probably want to rewrite all of this anyway. It's definitely simpler this way.

When we support dynamic messages, we'll need to modify JsonFormatter to handle enum values, as they won't come be "real" .NET enums at that point. It shouldn't be hard to do though.

2 files changed, 71 insertions, 0 deletions

diff --git a/csharp/src/Google.Protobuf.Test/Collections/MapFieldTest.cs b/csharp/src/Google.Protobuf.Test/Collections/MapFieldTest.cs
index 29c4c2a9..ba82c0e8 100644
--- a/csharp/src/Google.Protobuf.Test/Collections/MapFieldTest.cs
+++ b/csharp/src/Google.Protobuf.Test/Collections/MapFieldTest.cs
@@ -562,6 +562,20 @@ namespace Google.Protobuf.Collections
             Assert.IsFalse(values.Contains(null));
         }
 
+        [Test]
+        public void ToString_StringToString()
+        {
+            var map = new MapField<string, string> { { "foo", "bar" }, { "x", "y" } };
+            Assert.AreEqual("{ \"foo\": \"bar\", \"x\": \"y\" }", map.ToString());
+        }
+
+        [Test]
+        public void ToString_UnsupportedKeyType()
+        {
+            var map = new MapField<byte, string> { { 10, "foo" } };
+            Assert.Throws<ArgumentException>(() => map.ToString());
+        }
+
         private static KeyValuePair<TKey, TValue> NewKeyValuePair<TKey, TValue>(TKey key, TValue value)
         {
             return new KeyValuePair<TKey, TValue>(key, value);
diff --git a/csharp/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs b/csharp/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs
index 8c804fdd..8ed54cfb 100644
--- a/csharp/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs
+++ b/csharp/src/Google.Protobuf.Test/Collections/RepeatedFieldTest.cs
@@ -37,6 +37,7 @@ using System.IO;
 using System.Linq;
 using System.Text;
 using Google.Protobuf.TestProtos;
+using Google.Protobuf.WellKnownTypes;
 using NUnit.Framework;
 
 namespace Google.Protobuf.Collections
@@ -599,5 +600,61 @@ namespace Google.Protobuf.Collections
             list.Insert(1, "middle");
             CollectionAssert.AreEqual(new[] { "first", "middle", "second" }, list);
         }
+
+        [Test]
+        public void ToString_Integers()
+        {
+            var list = new RepeatedField<int> { 5, 10, 20 };
+            var text = list.ToString();
+            Assert.AreEqual("[ 5, 10, 20 ]", text);
+        }
+
+        [Test]
+        public void ToString_Strings()
+        {
+            var list = new RepeatedField<string> { "x", "y", "z" };
+            var text = list.ToString();
+            Assert.AreEqual("[ \"x\", \"y\", \"z\" ]", text);
+        }
+
+        [Test]
+        public void ToString_Messages()
+        {
+            var list = new RepeatedField<TestAllTypes> { new TestAllTypes { SingleDouble = 1.5 }, new TestAllTypes { SingleInt32 = 10 } };
+            var text = list.ToString();
+            Assert.AreEqual("[ { \"singleDouble\": 1.5 }, { \"singleInt32\": 10 } ]", text);
+        }
+
+        [Test]
+        public void ToString_Empty()
+        {
+            var list = new RepeatedField<TestAllTypes> { };
+            var text = list.ToString();
+            Assert.AreEqual("[ ]", text);
+        }
+
+        [Test]
+        public void ToString_InvalidElementType()
+        {
+            var list = new RepeatedField<decimal> { 15m };
+            Assert.Throws<ArgumentException>(() => list.ToString());
+        }
+
+        [Test]
+        public void ToString_Timestamp()
+        {
+            var list = new RepeatedField<Timestamp> { Timestamp.FromDateTime(new DateTime(2015, 10, 1, 12, 34, 56, DateTimeKind.Utc)) };
+            var text = list.ToString();
+            Assert.AreEqual("[ \"2015-10-01T12:34:56Z\" ]", text);
+        }
+
+        [Test]
+        public void ToString_Struct()
+        {
+            var message = new Struct { Fields = { { "foo", new Value { NumberValue = 20 } } } };
+            var list = new RepeatedField<Struct> { message };
+            var text = list.ToString();
+            Assert.AreEqual(text, "[ { \"foo\": 20 } ]", message.ToString());
+        }
     }
 }