Cache version strings after first generation.

src/generator/AutoRest.Go/CodeNamerGo.cs

@@ -11,6 +11,8 @@
 using AutoRest.Core.Utilities.Collections;
 using AutoRest.Core.Model;
 using AutoRest.Go.Model;
+using System.Text;
+using System.Text.RegularExpressions;
 
 namespace AutoRest.Go
 {
@@ -29,7 +31,7 @@ public class CodeNamerGo : CodeNamer
         public virtual IEnumerable<string> StandardImports => new string[] { "github.com/Azure/go-autorest/autorest/azure", "net/http" };
 
         public virtual IEnumerable<string> PageableImports => new string[] { "net/http", "github.com/Azure/go-autorest/autorest/to" };
-        
+
         public virtual IEnumerable<string> ValidationImport => new string[] { "github.com/Azure/go-autorest/autorest/validation" };
 
         // CommonInitialisms are those "words" within a name that Golint expects to be uppercase.
@@ -86,6 +88,9 @@ public class CodeNamerGo : CodeNamer
 
         public IReadOnlyDictionary<HttpStatusCode, string> StatusCodeToGoString;
 
+
+        private static readonly Regex semVerPattern = new Regex(@"^(?<major>\d+)\.(?<minor>\d+)\.(?<patch>\d+)(?:-(?<tag>\S+))?$", RegexOptions.Compiled);
+
         /// <summary>
         /// Initializes a new instance of CodeNamerGo.
         /// </summary>
@@ -412,20 +417,12 @@ public void ReserveNamespace(string ns)
         // camelCase or PascalCase.
         private string EnsureNameCase(string name)
         {
-            List<string> words = new List<string>();
-            new List<string>(name.ToWords())
-                .ForEach(s =>
-                {
-                    if (CommonInitialisms.Contains(s))
-                    {
-                        words.Add(s.ToUpper());
-                    }
-                    else
-                    {
-                        words.Add(s);
-                    }
-                });
-            return String.Join(String.Empty, words.ToArray());
+            var builder = new StringBuilder();
+            foreach (var s in name.ToWords())
+            {
+                builder.Append(CommonInitialisms.Contains(s) ? s.ToUpper() : s);
+            }
+            return builder.ToString();
         }
 
         public static string[] SDKVersionFromPackageVersion(string v)
@@ -434,12 +431,19 @@ public static string[] SDKVersionFromPackageVersion(string v)
             {
                 throw new ArgumentNullException("package version");
             }
-            string[] version = v.Split('.');
-            if (version.Length != 3)
+
+            var ver = semVerPattern.Match(v);
+
+            if (ver.Success)
             {
-                throw new InvalidOperationException("version string should have major, minor and patch versions.");
+                var tagVal = ver.Groups["tag"].Success ? ver.Groups["tag"].Value : "";
+                return new[] { ver.Groups["major"].Value, ver.Groups["minor"].Value, ver.Groups["patch"].Value, tagVal };
+
             }
-            return version;
+            throw new ArgumentException(
+                paramName: nameof(v),
+                message: "Version strings should be either of the format \"<major>.<minor>.<patch>\" or \"<major>.<minor>.<patch>-<tag>\". Where major, minor, and patch are decimal numbers and tag does not include whitespace.");
+
         }
 
         public override string EscapeDefaultValue(string defaultValue, IModelType type)

src/generator/AutoRest.Go/Templates/VersionTemplate.cshtml

@@ -13,29 +13,46 @@ package @Model.Namespace
 
 @EmptyLine
 import (
+    "bytes"
     "fmt"
+    "strings"
 )
 @EmptyLine
 
 const (
     major = "@(Model.Version[0])"
     minor = "@(Model.Version[1])"
     patch = "@(Model.Version[2])"
-    // Always begin a "tag" with a dash (as per http://semver.org)
-    tag   = "-beta"
+    tag   = "@(Model.Version[3])"
 
-    semVerFormat = "%s.%s.%s%s"
     userAgentFormat = "Azure-SDK-For-Go/%s arm-%s/%s"
 )
 
+// cached results of UserAgent and Version to prevent repeated operations.
+var (
+    userAgent string
+    version string
+)
+
 @EmptyLine
 // UserAgent returns the UserAgent string to use when sending http.Requests.
 func UserAgent() string {
-    return fmt.Sprintf(userAgentFormat, Version(), "@(Model.Namespace)", "@(Model.ApiVersion)")
+    if userAgent == "" {
+        userAgent = fmt.Sprintf(userAgentFormat, Version(), "@(Model.Namespace)", "@(Model.ApiVersion)")
+    }
+    return userAgent
 }
 
 @EmptyLine
 // Version returns the semantic version (see http://semver.org) of the client.
 func Version() string {
-    return fmt.Sprintf(semVerFormat, major, minor, patch, tag)
+    if version == "" {
+        versionBuilder := bytes.NewBufferString(fmt.Sprintf("%d.%d.%d", major, minor, patch))
+        if tag != "" {
+            versionBuilder.WriteRune('-')
+            versionBuilder.WriteString(strings.TrimPrefix(tag, "-"))
+        }
+        version = string(versionBuilder.Bytes())
+    }
+    return version
 }