feat: Add a FieldFormats static class for auto-populated fields

Google.Api.Gax.Tests/FieldFormatsTest.cs

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2024 Google LLC
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file or at
+ * https://developers.google.com/open-source/licenses/bsd
+ */
+
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.RegularExpressions;
+using Xunit;
+
+namespace Google.Api.Gax.Tests;
+
+public class FieldFormatsTest
+{
+    [Fact]
+    public void GenerateUuid4()
+    {
+        // We generate lots of values to check both uniqueness and formatting.
+        int count = 10_000;
+        var strings = new HashSet<string>(Enumerable.Range(0, count).Select(_ => FieldFormats.GenerateUuid4()));
+        Assert.Equal(count, strings.Count);
+
+        var pattern = new Regex("^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$");
+        Assert.All(strings, x => Assert.Matches(pattern, x));
+    }
+}

Google.Api.Gax.Tests/Google.Api.Gax.Tests.csproj

@@ -5,7 +5,7 @@
   <PropertyGroup>
     <TargetFrameworks>net6.0;net462</TargetFrameworks>
     <TargetFrameworks Condition="'$(OS)' != 'Windows_NT'">net6.0</TargetFrameworks>
-    <LangVersion>8.0</LangVersion>
+    <LangVersion>latest</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>

Google.Api.Gax/FieldFormats.cs

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2024 Google LLC
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file or at
+ * https://developers.google.com/open-source/licenses/bsd
+ */
+
+using System;
+
+namespace Google.Api.Gax;
+
+/// <summary>
+/// Convenience methods for handling field formats documented in https://google.aip.dev/202.
+/// </summary>
+public static class FieldFormats
+{
+    /// <summary>
+    /// Generates a UUID v4 value and formats it as xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx,
+    /// using lower-case letters for hex digits.
+    /// </summary>
+    public static string GenerateUuid4() => Guid.NewGuid().ToString();
+}