Add string extension methods to validate spec versions for easy reuse

Author: MaggieKimani1

src/Microsoft.OpenApi.Readers/OpenApiVersionExtensionMethods.cs

@@ -0,0 +1,59 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license.
+
+namespace Microsoft.OpenApi.Readers
+{
+    /// <summary>
+    /// Generates custom extension methods for the version string type
+    /// </summary>
+    public static class OpenApiVersionExtensionMethods
+    {
+        /// <summary>
+        /// Extension method for Spec version 2.0
+        /// </summary>
+        /// <param name="version"></param>
+        /// <returns></returns>
+        public static bool is2_0(this string version)
+        {
+            bool result = false;
+            if (version.Equals("2.0"))
+            {
+                result = true;
+            }
+            
+            return result;
+        }
+
+        /// <summary>
+        /// Extension method for Spec version 3.0
+        /// </summary>
+        /// <param name="version"></param>
+        /// <returns></returns>
+        public static bool is3_0(this string version)
+        {
+            bool result = false;
+            if (version.StartsWith("3.0"))
+            {
+                result = true;
+            }
+
+            return result;
+        }
+
+        /// <summary>
+        /// Extension method for Spec version 3.1
+        /// </summary>
+        /// <param name="version"></param>
+        /// <returns></returns>
+        public static bool is3_1(this string version)
+        {
+            bool result = false;
+            if (version.StartsWith("3.1"))
+            {
+                result = true;
+            }
+
+            return result;
+        }
+    }
+}

src/Microsoft.OpenApi.Readers/ParsingContext.cs

@@ -59,14 +59,14 @@ internal OpenApiDocument Parse(YamlDocument yamlDocument)
 
             switch (inputVersion)
             {
-                case string version when version == "2.0":
+                case string version when version.is2_0():
                     VersionService = new OpenApiV2VersionService(Diagnostic);
                     doc = VersionService.LoadDocument(RootNode);
                     this.Diagnostic.SpecificationVersion = OpenApiSpecVersion.OpenApi2_0;
                     ValidateRequiredFields(doc, version);
                     break;
 
-                case string version when version.StartsWith("3.0") || version.StartsWith("3.1"):
+                case string version when version.is3_0() || version.is3_1():
                     VersionService = new OpenApiV3VersionService(Diagnostic);
                     doc = VersionService.LoadDocument(RootNode);
                     this.Diagnostic.SpecificationVersion = OpenApiSpecVersion.OpenApi3_0;
@@ -248,12 +248,12 @@ public void PopLoop(string loopid)
 
         private void ValidateRequiredFields(OpenApiDocument doc, string version)
         {
-            if ((version == "2.0" || version.StartsWith("3.0")) && (doc.Paths == null || !doc.Paths.Any()))
+            if ((version.is2_0() || version.is3_0()) && (doc.Paths == null || !doc.Paths.Any()))
             {
                 // paths is a required field in OpenAPI 3.0 but optional in 3.1
                 RootNode.Context.Diagnostic.Errors.Add(new OpenApiError("", $"Paths is a REQUIRED field at {RootNode.Context.GetLocation()}"));
             }
-            else if (version.StartsWith("3.1") && (doc.Paths == null || !doc.Paths.Any()) && (doc.Webhooks == null || !doc.Webhooks.Any()))
+            else if (version.is3_1() && (doc.Paths == null || !doc.Paths.Any()) && (doc.Webhooks == null || !doc.Webhooks.Any()))
             {
                 RootNode.Context.Diagnostic.Errors.Add(new OpenApiError(
                     "", $"The document MUST contain either a Paths or Webhooks field at {RootNode.Context.GetLocation()}"));