feat: better handling of enum changes based on direction

| Enum Change   | In Request (path/query/body) | In Response (body) | In Both  |
|---------------|------------------------------|--------------------|----------|
| Value Added   | OK                           | Breaking           | Breaking |
| Value Removed | Breaking                     | OK                 | Breaking |

src/Criteo.OpenApi.Comparator.UTest/OpenApiEnumDirectionTests.cs

@@ -0,0 +1,92 @@
+// Copyright (c) Criteo Technology. All rights reserved.
+// Licensed under the Apache 2.0 License. See LICENSE in the project root for license information.
+
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+using Criteo.OpenApi.Comparator.Logging;
+using NUnit.Framework;
+
+namespace Criteo.OpenApi.Comparator.UTest;
+
+[TestFixture]
+public class OpenApiEnumDirectionTests
+{
+    [TestCase("old_without_refs", "path_add", "#/paths/~1order~1{path}/post/parameters/0/schema/enum")]
+    [TestCase("old_without_refs", "query_add", "#/paths/~1order~1{path}/post/parameters/1/schema/enum")]
+    [TestCase("old_without_refs", "body_add", "#/paths/~1order~1{path}/post/requestBody/content/application~1json/schema/properties/foo/enum")]
+    [TestCase("old_with_refs", "request_ref_add", "#/paths/~1order~1{path}/post/parameters/0/schema/enum")]
+    public void CompareOAS_ShouldReturn_NonBreaking_AddedEnumValueChange(string oldName, string newName, string jsonRef, int expectedDifferencesCount = 1)
+    {
+        var differences = CompareSpecifications(oldName, newName);
+        differences.AssertContains(new ExpectedDifference
+        {
+            Rule = ComparisonRules.AddedEnumValue,
+            Severity = Severity.Warning,
+            NewJsonRef = jsonRef
+        }, expectedDifferencesCount);
+    }
+
+
+    [TestCase("old_without_refs", "response_add", "#/paths/~1order~1{path}/post/responses/200/content/application~1json/schema/properties/bar/enum")]
+    [TestCase("old_with_refs", "response_ref_add", "#/paths/~1order~1{path}/post/responses/200/content/application~1json/schema/properties/bar/enum")]
+    [TestCase("old_with_refs", "both_ref_add", "#/paths/~1order~1{path}/post/responses/200/content/application~1json/schema/properties/foo/enum", 2)]
+    public void CompareOAS_ShouldReturn_Breaking_AddedEnumValueChange(string oldName, string newName, string jsonRef, int expectedDifferencesCount = 1)
+    {
+        var differences = CompareSpecifications(oldName, newName);
+        differences.AssertContains(new ExpectedDifference
+        {
+            Rule = ComparisonRules.AddedEnumValue,
+            Severity = Severity.Error,
+            NewJsonRef = jsonRef
+        }, expectedDifferencesCount);
+    }
+
+    [TestCase("old_without_refs", "response_remove", "#/paths/~1order~1{path}/post/responses/200/content/application~1json/schema/properties/bar/enum")]
+    [TestCase("old_with_refs", "response_ref_remove", "#/paths/~1order~1{path}/post/responses/200/content/application~1json/schema/properties/bar/enum")]
+    public void CompareOAS_ShouldReturn_NonBreaking_RemovedEnumValueChange(string oldName, string newName, string jsonRef, int expectedDifferencesCount = 1)
+    {
+        var differences = CompareSpecifications(oldName, newName);
+        differences.AssertContains(new ExpectedDifference
+        {
+            Rule = ComparisonRules.RemovedEnumValue,
+            Severity = Severity.Warning,
+            NewJsonRef = jsonRef
+        }, expectedDifferencesCount);
+    }
+
+    [TestCase("old_without_refs", "path_remove", "#/paths/~1order~1{path}/post/parameters/0/schema/enum")]
+    [TestCase("old_without_refs", "query_remove", "#/paths/~1order~1{path}/post/parameters/1/schema/enum")]
+    [TestCase("old_without_refs", "body_remove", "#/paths/~1order~1{path}/post/requestBody/content/application~1json/schema/properties/foo/enum")]
+    [TestCase("old_with_refs", "request_ref_remove", "#/paths/~1order~1{path}/post/parameters/0/schema/enum")]
+    [TestCase("old_with_refs", "both_ref_remove", "#/paths/~1order~1{path}/post/requestBody/content/application~1json/schema/properties/foo/enum")]
+    public void CompareOAS_ShouldReturn_Breaking_RemovedEnumValueChange(string oldName, string newName, string jsonRef, int expectedDifferencesCount = 1)
+    {
+        var differences = CompareSpecifications(oldName, newName);
+        differences.AssertContains(new ExpectedDifference
+        {
+            Rule = ComparisonRules.RemovedEnumValue,
+            Severity = Severity.Error,
+            NewJsonRef = jsonRef,
+        }, expectedDifferencesCount);
+    }
+
+    private static IList<ComparisonMessage> CompareSpecifications(string oldName, string newName)
+    {
+        var baseDirectory = Directory
+            .GetParent(typeof(OpenApiSpecificationsCompareTests).GetTypeInfo().Assembly.Location)
+            .ToString();
+
+        var oldFileName = Path.Combine(baseDirectory, "Resource", "enum_direction", oldName + ".json");
+        var newFileName = Path.Combine(baseDirectory, "Resource", "enum_direction", newName + ".yaml");
+
+        var differences = OpenApiComparator
+            .Compare(File.ReadAllText(oldFileName), File.ReadAllText(newFileName), strict: true)
+            .ToList();
+
+        OpenApiSpecificationsCompareTests.ValidateDifferences(differences);
+
+        return differences;
+    }
+}

src/Criteo.OpenApi.Comparator.UTest/OpenApiSpecificationsCompareTests.cs

@@ -315,12 +315,12 @@ public void CompareOAS_ShouldReturn_RemovedEnumValueDifferences()
                 Rule = ComparisonRules.RemovedEnumValue,
                 Severity = Severity.Warning,
                 OldJsonRef = "#/paths/~1api~1Parameters/put/parameters/0/schema/enum"
-            }, 2);
+            }, 3);
             differences.AssertContains(new ExpectedDifference
             {
                 Rule = ComparisonRules.ConstraintIsStronger,
                 Severity = Severity.Info,
-            }, 2);
+            }, 3);
         }
 
         [Test]
@@ -333,12 +333,12 @@ public void CompareOAS_ShouldReturn_AddedEnumValueDifferences()
                 Rule = ComparisonRules.AddedEnumValue,
                 Severity = Severity.Warning,
                 NewJsonRef = "#/paths/~1api~1Parameters/put/responses/200/content/application~1json/schema/properties/petType/enum"
-            }, 1);
+            }, 2);
             differences.AssertContains(new ExpectedDifference
             {
                 Rule = ComparisonRules.ConstraintIsWeaker,
                 Severity = Severity.Info,
-            }, 2);
+            }, 4);
         }
 
         [Test]
@@ -627,12 +627,12 @@ public void CompareOAS_ShouldReturn_OneMessagePerRule_When_RecursiveModel()
                 Rule = ComparisonRules.RemovedProperty,
                 Severity = Severity.Warning,
                 OldJsonRef = "#/paths/~1api~1Operations/post/parameters/0/schema/properties/error/properties/target"
-            }, 1);
+            }, 2);
             differences.AssertContains(new ExpectedDifference
             {
                 Rule = ComparisonRules.ReadonlyPropertyChanged,
                 Severity = Severity.Warning,
-            }, 1);
+            }, 2);
         }
 
         [Test]
@@ -859,7 +859,7 @@ private static void ValidateMessage(ComparisonMessage message)
             }
         }
 
-        private static void ValidateDifferences(IEnumerable<ComparisonMessage> differences)
+        internal static void ValidateDifferences(IEnumerable<ComparisonMessage> differences)
         {
             foreach (var message in differences)
             {

src/Criteo.OpenApi.Comparator.UTest/Resource/enum_direction/body_add.yaml

@@ -0,0 +1,46 @@
+openapi: 3.0.0
+info:
+  title: My API
+  version: 0.2.0
+paths:
+  /order/{path}:
+    post:
+      parameters:
+        - name: path
+          in: path
+          required: true
+          schema:
+            type: string
+            enum:
+              - abc
+              - def
+        - name: query
+          in: query
+          schema:
+            type: string
+            enum:
+              - ghi
+              - jkl
+      requestBody:
+        content:
+          application/json:
+            schema:
+              properties:
+                foo:
+                  type: string
+                  enum:
+                    - zzzzzz
+                    - mno
+                    - pqr
+      responses:
+        "200":
+          description: Successful Response
+          content:
+            application/json:
+              schema:
+                properties:
+                  bar:
+                    type: string
+                    enum:
+                      - stu
+                      - vwx

src/Criteo.OpenApi.Comparator.UTest/Resource/enum_direction/body_remove.yaml

@@ -0,0 +1,44 @@
+openapi: 3.0.0
+info:
+  title: My API
+  version: 0.2.0
+paths:
+  /order/{path}:
+    post:
+      parameters:
+        - name: path
+          in: path
+          required: true
+          schema:
+            type: string
+            enum:
+              - abc
+              - def
+        - name: query
+          in: query
+          schema:
+            type: string
+            enum:
+              - ghi
+              - jkl
+      requestBody:
+        content:
+          application/json:
+            schema:
+              properties:
+                foo:
+                  type: string
+                  enum:
+                    - pqr
+      responses:
+        "200":
+          description: Successful Response
+          content:
+            application/json:
+              schema:
+                properties:
+                  bar:
+                    type: string
+                    enum:
+                      - stu
+                      - vwx

src/Criteo.OpenApi.Comparator.UTest/Resource/enum_direction/both_ref_add.yaml

@@ -0,0 +1,49 @@
+openapi: 3.0.0
+info:
+  title: My API
+  version: 0.2.0
+paths:
+  /order/{path}:
+    post:
+      parameters:
+        - name: path
+          in: path
+          required: true
+          schema:
+            $ref: "#/components/schemas/RequestOnlyEnum"
+      requestBody:
+        content:
+          application/json:
+            schema:
+              properties:
+                foo:
+                  $ref: "#/components/schemas/RequestResponseEnum"
+      responses:
+        "200":
+          description: Successful Response
+          content:
+            application/json:
+              schema:
+                properties:
+                  foo:
+                    $ref: "#/components/schemas/RequestResponseEnum"
+                  bar:
+                    $ref: "#/components/schemas/ResponseOnlyEnum"
+components:
+  schemas:
+    RequestOnlyEnum:
+      type: string
+      enum:
+        - abc
+        - def
+    ResponseOnlyEnum:
+      type: string
+      enum:
+        - ghi
+        - jkl
+    RequestResponseEnum:
+      type: string
+      enum:
+        - zzzzzz
+        - mno
+        - pqr

src/Criteo.OpenApi.Comparator.UTest/Resource/enum_direction/both_ref_remove.yaml

@@ -0,0 +1,47 @@
+openapi: 3.0.0
+info:
+  title: My API
+  version: 0.2.0
+paths:
+  /order/{path}:
+    post:
+      parameters:
+        - name: path
+          in: path
+          required: true
+          schema:
+            $ref: "#/components/schemas/RequestOnlyEnum"
+      requestBody:
+        content:
+          application/json:
+            schema:
+              properties:
+                foo:
+                  $ref: "#/components/schemas/RequestResponseEnum"
+      responses:
+        "200":
+          description: Successful Response
+          content:
+            application/json:
+              schema:
+                properties:
+                  foo:
+                    $ref: "#/components/schemas/RequestResponseEnum"
+                  bar:
+                    $ref: "#/components/schemas/ResponseOnlyEnum"
+components:
+  schemas:
+    RequestOnlyEnum:
+      type: string
+      enum:
+        - abc
+        - def
+    ResponseOnlyEnum:
+      type: string
+      enum:
+        - ghi
+        - jkl
+    RequestResponseEnum:
+      type: string
+      enum:
+        - pqr