From c76cb9248de8966b25bc08b098b88d6734b96d09 Mon Sep 17 00:00:00 2001
From: "N. Taylor Mullen" <nimullen@microsoft.com>
Date: Wed, 24 Jul 2019 16:21:19 -0700
Subject: [PATCH] Add support for increment/decrement [Parameter] usage
 detection.

- Didn't realize there was an increment or decrement operation kind.
- Added tests to cover this scenario

#12543
---
 .../src/ComponentParameterUsageAnalyzer.cs    | 16 ++++-
 .../ComponentParameterUsageAnalyzerTest.cs    | 63 +++++++++++++++++++
 2 files changed, 76 insertions(+), 3 deletions(-)

diff --git a/src/Components/Analyzers/src/ComponentParameterUsageAnalyzer.cs b/src/Components/Analyzers/src/ComponentParameterUsageAnalyzer.cs
index 0d45edcabc..8df3167b83 100644
--- a/src/Components/Analyzers/src/ComponentParameterUsageAnalyzer.cs
+++ b/src/Components/Analyzers/src/ComponentParameterUsageAnalyzer.cs
@@ -38,8 +38,18 @@ namespace Microsoft.AspNetCore.Components.Analyzers
                 {
                     startBlockContext.RegisterOperationAction(context =>
                     {
-                        var assignmentOperation = (IAssignmentOperation)context.Operation;
-                        var leftHandSide = assignmentOperation.Target;
+                        IOperation leftHandSide;
+
+                        if (context.Operation is IAssignmentOperation assignmentOperation)
+                        {
+                            leftHandSide = assignmentOperation.Target;
+                        }
+                        else
+                        {
+                            var incrementOrDecrementOperation = (IIncrementOrDecrementOperation)context.Operation;
+                            leftHandSide = incrementOrDecrementOperation.Target;
+                        }
+
                         if (leftHandSide == null)
                         {
                             // Malformed assignment, no left hand side.
@@ -96,7 +106,7 @@ namespace Microsoft.AspNetCore.Components.Analyzers
                             DiagnosticDescriptors.ComponentParametersShouldNotBeSetOutsideOfTheirDeclaredComponent,
                             propertyReference.Syntax.GetLocation(),
                             propertyReference.Member.Name));
-                    }, OperationKind.SimpleAssignment, OperationKind.CompoundAssignment, OperationKind.CoalesceAssignment);
+                    }, OperationKind.SimpleAssignment, OperationKind.CompoundAssignment, OperationKind.CoalesceAssignment, OperationKind.Increment, OperationKind.Decrement);
                 });
             });
         }
diff --git a/src/Components/Analyzers/test/ComponentParameterUsageAnalyzerTest.cs b/src/Components/Analyzers/test/ComponentParameterUsageAnalyzerTest.cs
index db664a2e76..d1c2d2bede 100644
--- a/src/Components/Analyzers/test/ComponentParameterUsageAnalyzerTest.cs
+++ b/src/Components/Analyzers/test/ComponentParameterUsageAnalyzerTest.cs
@@ -19,6 +19,7 @@ namespace Microsoft.AspNetCore.Components.Analyzers
         class TestComponent : IComponent
         {{
             [Parameter] public string TestProperty {{ get; set; }}
+            [Parameter] public int TestInt {{ get; set; }}
             public string NonParameter {{ get; set; }}
         }}
     }}" + ComponentsTestDeclarations.Source;
@@ -119,6 +120,68 @@ namespace Microsoft.AspNetCore.Components.Analyzers
                 });
         }
 
+        [Fact]
+        public void ComponentPropertyIncrement_Warns()
+        {
+            var test = $@"
+    namespace ConsoleApplication1
+    {{
+        using {typeof(ParameterAttribute).Namespace};
+        class OtherComponent : IComponent
+        {{
+            private TestComponent _testComponent;
+            void Render()
+            {{
+                _testComponent = new TestComponent();
+                _testComponent.TestInt++;
+            }}
+        }}
+    }}" + ComponentTestSource;
+
+            VerifyCSharpDiagnostic(test,
+                new DiagnosticResult
+                {
+                    Id = DiagnosticDescriptors.ComponentParametersShouldNotBeSetOutsideOfTheirDeclaredComponent.Id,
+                    Message = "Component parameter 'TestInt' should not be set outside of its component.",
+                    Severity = DiagnosticSeverity.Warning,
+                    Locations = new[]
+                    {
+                        new DiagnosticResultLocation("Test0.cs", 11, 17)
+                    }
+                });
+        }
+
+        [Fact]
+        public void ComponentPropertyDecrement_Warns()
+        {
+            var test = $@"
+    namespace ConsoleApplication1
+    {{
+        using {typeof(ParameterAttribute).Namespace};
+        class OtherComponent : IComponent
+        {{
+            private TestComponent _testComponent;
+            void Render()
+            {{
+                _testComponent = new TestComponent();
+                _testComponent.TestInt--;
+            }}
+        }}
+    }}" + ComponentTestSource;
+
+            VerifyCSharpDiagnostic(test,
+                new DiagnosticResult
+                {
+                    Id = DiagnosticDescriptors.ComponentParametersShouldNotBeSetOutsideOfTheirDeclaredComponent.Id,
+                    Message = "Component parameter 'TestInt' should not be set outside of its component.",
+                    Severity = DiagnosticSeverity.Warning,
+                    Locations = new[]
+                    {
+                        new DiagnosticResultLocation("Test0.cs", 11, 17)
+                    }
+                });
+        }
+
         [Fact]
         public void ComponentPropertyExpression_Ignores()
         {