Add reserved fields to proto generator

src/Abc.Zebus.MessageDsl.Tests/MessageDsl/GeneratorTests.cs

@@ -19,13 +19,15 @@ static GeneratorTests()
     protected abstract string SnapshotExtension { get; }
     protected abstract string GenerateRaw(ParsedContracts contracts);
 
+    [MustUseReturnValue]
     protected string Generate(MessageDefinition message)
     {
         var contracts = new ParsedContracts();
         contracts.Messages.Add(message);
         return Generate(contracts);
     }
 
+    [MustUseReturnValue]
     protected string Generate(ParsedContracts contracts)
     {
         PreProcess(contracts);
@@ -40,15 +42,13 @@ protected string Generate(ParsedContracts contracts)
         return result;
     }
 
-    [MustUseReturnValue]
     protected Task<string> Verify(MessageDefinition message)
     {
         var contracts = new ParsedContracts();
         contracts.Messages.Add(message);
         return Verify(contracts);
     }
 
-    [MustUseReturnValue]
     protected async Task<string> Verify(ParsedContracts contracts)
     {
         PreProcess(contracts);

src/Abc.Zebus.MessageDsl.Tests/MessageDsl/ProtoGeneratorTests.cs

@@ -1,4 +1,5 @@
 using System.Threading.Tasks;
+using Abc.Zebus.MessageDsl.Analysis;
 using Abc.Zebus.MessageDsl.Ast;
 using Abc.Zebus.MessageDsl.Generator;
 using Abc.Zebus.MessageDsl.Tests.TestTools;
@@ -190,6 +191,31 @@ public async Task should_handle_message_inheritance()
         code.ShouldContain("optional MsgC _subTypeMsgC = 11;");
     }
 
+    [Test]
+    public async Task should_generate_reservations()
+    {
+        await Verify(new MessageDefinition
+        {
+            Name = "MsgA",
+            Parameters =
+            {
+                new ParameterDefinition("int?", "foo"),
+            },
+            ReservedRanges =
+            {
+                new ReservationRange(2),
+                new ReservationRange(10, 15),
+                new ReservationRange(8, 14),
+                new ReservationRange(16),
+                new ReservationRange(42)
+            },
+            Options =
+            {
+                Proto = true
+            }
+        });
+    }
+
     protected override string SnapshotExtension => "proto";
 
     protected override string GenerateRaw(ParsedContracts contracts)

src/Abc.Zebus.MessageDsl.Tests/MessageDsl/ReservationRangeTests.cs

@@ -0,0 +1,18 @@
+using Abc.Zebus.MessageDsl.Analysis;
+using Abc.Zebus.MessageDsl.Tests.TestTools;
+using NUnit.Framework;
+
+namespace Abc.Zebus.MessageDsl.Tests.MessageDsl;
+
+[TestFixture]
+public class ReservationRangeTests
+{
+    [Test]
+    public void should_compress_ranges()
+    {
+        ReservationRange.Compress([new(2, 4), new(3, 5), new(6, 7), new(10, 12)])
+                        .ShouldEqual([new(2, 7), new(10, 12)]);
+
+        ReservationRange.Compress([]).ShouldEqual([]);
+    }
+}

src/Abc.Zebus.MessageDsl.Tests/MessageDsl/Snapshots/ProtoGeneratorTests.should_generate_reservations.verified.proto

@@ -0,0 +1,11 @@
+
+// Generated by Abc.Zebus.MessageDsl v1.2.3.4
+
+import "servicebus.proto";
+
+message MsgA {
+    option (servicebus.message).type = Event;
+
+    reserved 2, 8 to 16, 42;
+    optional int32 Foo = 1;
+}

src/Abc.Zebus.MessageDsl/Analysis/ReservationRange.cs

@@ -1,11 +1,17 @@
-using Abc.Zebus.MessageDsl.Ast;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Abc.Zebus.MessageDsl.Ast;
 
 namespace Abc.Zebus.MessageDsl.Analysis;
 
 internal readonly struct ReservationRange(int startTag, int endTag)
 {
     public static ReservationRange None => default;
 
+    public int StartTag => startTag;
+    public int EndTag => endTag;
+
     private bool IsValid => startTag > 0;
 
     public ReservationRange(int tag)
@@ -37,6 +43,32 @@ public void AddToMessage(MessageDefinition message)
         message.ReservedRanges.Add(this);
     }
 
+    public static IEnumerable<ReservationRange> Compress(IEnumerable<ReservationRange> ranges)
+    {
+        var startTag = 0;
+        var endTag = 0;
+
+        foreach (var range in ranges.Where(i => i.IsValid).OrderBy(i => i.StartTag))
+        {
+            if (startTag == 0)
+            {
+                startTag = range.StartTag;
+                endTag = range.EndTag;
+            }
+
+            if (range.StartTag > endTag + 1)
+            {
+                yield return new ReservationRange(startTag, endTag);
+                startTag = range.StartTag;
+            }
+
+            endTag = Math.Max(endTag, range.EndTag);
+        }
+
+        if (startTag != 0)
+            yield return new ReservationRange(startTag, endTag);
+    }
+
     public override string ToString()
         => IsValid
             ? startTag != endTag

src/Abc.Zebus.MessageDsl/Generator/ProtoGenerator.cs

@@ -85,6 +85,7 @@ private void WriteMessage(MessageDefinition message)
         using (Block())
         {
             WriteMessageOptions(message);
+            WriteReservedFields(message);
 
             foreach (var param in message.Parameters)
                 WriteField(param);
@@ -109,6 +110,30 @@ private void WriteMessageOptions(MessageDefinition message)
         }
     }
 
+    private void WriteReservedFields(MessageDefinition message)
+    {
+        if (message.ReservedRanges.Count == 0)
+            return;
+
+        Writer.Write("reserved ");
+        var first = true;
+
+        foreach (var reservation in ReservationRange.Compress(message.ReservedRanges))
+        {
+            if (first)
+                first = false;
+            else
+                Writer.Write(", ");
+
+            if (reservation.StartTag == reservation.EndTag)
+                Writer.Write(reservation.StartTag);
+            else
+                Writer.Write("{0} to {1}", reservation.StartTag, reservation.EndTag);
+        }
+
+        Writer.WriteLine(";");
+    }
+
     private void WriteField(ParameterDefinition param)
     {
         Writer.Write(