Parse oneof before field, so that 'oneof' isn't considered a messag…

…e-type in proto3. (#89)

Proto3 fields don't have a label qualifier (optional | repeated | required) to distinguish between those and 'oneof', so it was being treated as a field-type identifier.

Fixes #88

Parser.Test/TestParser.fs

@@ -480,6 +480,17 @@ module Message =
         |> should equal
         <| TOneOf("MyOneof", [ TOneOfField("name",TString,1u,[("foo",TStrLit("bar"))]) ])
 
+    [<Fact>]
+    let ``Parse oneof with multiple cases`` () =
+        Parse.fromStringWithParser (ws >>. pOneOf) """
+            oneof test_oneof {
+                string name = 4;
+                int32 age = 9;
+            }
+            """
+        |> should equal
+        <| TOneOf("test_oneof", [ TOneOfField("name",TString,4u,[]); TOneOfField("age",TInt32,9u,[]) ])
+
     [<Fact>]
     let ``Parse map`` () =
         Parse.fromStringWithParser (ws >>. pMap) """
@@ -1043,3 +1054,33 @@ module Proto2 =
 		        }
             """ |> ignore
         |> should not' (throw typeof<System.FormatException>)
+
+[<Xunit.Trait("Kind", "Unit")>]
+module RegressionTests =
+
+    [<Fact>]
+    let ``proto3 oneof type doesn't parse (#88)`` () =
+        System.Diagnostics.Debugger.Break()
+        Parse.fromStringWithParser pProto """
+            syntax = "proto3";
+
+            message SampleMessage {
+                oneof test_oneof {
+                  string name = 4;
+                  int32 age = 9;
+                  }
+            }
+        """
+        |> should equal (
+            [
+                TSyntax TProto3
+                TMessage ("SampleMessage",
+                    [
+                        TOneOf("test_oneof",
+                            [
+                                TOneOfField("name",TString,4u,[])
+                                TOneOfField("age",TInt32,9u,[])
+                            ])
+
+                    ])
+            ])

Parser/Parser.fs

@@ -359,7 +359,7 @@ module Parse =
             //let todoMsg = "Explicit 'optional' fields are prohibited in proto3 syntax.  Since all fields are optional by default, the 'optional' label should simply be removed."
             (opt (str_ws1 "repeated" >>% TRepeated)) |>> defArg TOptional
 
-        /// Parser for proto2 lable + ws
+        /// Parser for proto2 label + ws
         let pLabel_ws1 = pLabel .>> ws1
 
         /// Parser for types: double | int32 | etc...
@@ -481,13 +481,13 @@ module Parse =
 
             choice [
                 (isProto2 >>. pGroup) // must be parsed first to avoid confusion
+                pOneOf                // must be parsed before pField, so 'oneof' isn't considered a type in Proto3
                 pField
                 pMessageEnum
                 pMessageMessage
                 (isProto2 >>. pMessageExtend)
                 (isProto2 >>. pExtensions)
                 pMessageOption
-                pOneOf
                 pMap
                 pReserved
                 ]