Merge pull request #537 from manfred-brands/issue-344

Within usage analyzer + tests + codefix

.editorconfig

@@ -97,6 +97,7 @@ dotnet_style_collection_initializer = true:none
 dotnet_style_coalesce_expression = true:warning
 dotnet_style_null_propagation = true:warning
 dotnet_style_explicit_tuple_names = true:warning
+dotnet_style_prefer_is_null_check_over_reference_equality_method = true:warning
 
 # Expression-bodied members
 csharp_style_expression_bodied_accessors = when_on_single_line:warning
@@ -131,6 +132,12 @@ dotnet_naming_rule.parameters_and_locals.severity = warning
 dotnet_naming_rule.parameters_and_locals.symbols = parameters_and_locals
 dotnet_naming_rule.parameters_and_locals.style = camel_case
 
+##################################################################################
+# IDE Code Style Analyzers
+
+# IDE0041: Use 'is null' check
+dotnet_diagnostic.IDE0041.severity = warning
+
 # IDE0046: Convert to conditional expression
 # Complex Conditional expressions are not easier to read
 dotnet_diagnostic.IDE0046.severity = none
@@ -237,3 +244,11 @@ dotnet_diagnostic.CA1310.severity = error
 # Default severity for analyzer diagnostics with category 'MicrosoftCodeAnalysisReleaseTracking'
 dotnet_analyzer_diagnostic.category-MicrosoftCodeAnalysisReleaseTracking.severity = none
 
+##################################################################################
+# CSharpIsNull Analyzers
+
+# CSIsNull001: Use `is null` for null checks
+dotnet_diagnostic.CSIsNull001.severity = warning
+
+# CSIsNull002: Use `is object` for non-null checks
+dotnet_diagnostic.CSIsNull002.severity = warning

documentation/NUnit2047.md

@@ -0,0 +1,96 @@
+# NUnit2047
+
+## Incompatible types for Within constraint
+
+| Topic    | Value
+| :--      | :--
+| Id       | NUnit2047
+| Severity | Warning
+| Enabled  | True
+| Category | Assertion
+| Code     | [WithinUsageAnalyzer](https://github.com/nunit/nunit.analyzers/blob/master/src/nunit.analyzers/WithinUsage/WithinUsageAnalyzer.cs)
+
+## Description
+
+The `Within` modifier should only be used for numeric or Date/Time arguments or tuples containing only these element types. Using it on other types will not have any effect.
+
+## Motivation
+
+To bring developers' attention to a scenario in which their code is actually having no effect and may reveal that their test is not doing what they expect.
+
+## How to fix violations
+
+### Example Violation
+
+```csharp
+[Test]
+public void RecordsEqualsMismatch()
+{
+    var a = new Data(1, 1.0);
+    var b = new Data(1, 1.1);
+
+    Assert.That(a, Is.EqualTo(b).Within(0.2), $"{a} != {b}");
+}
+
+private sealed record Data(int number, double Value);
+```
+
+### Explanation
+
+Using `Within` here doesn't make any sense, because NUnit cannot apply comparison with tolerance to the types we're comparing.
+
+### Fix
+
+Remove the errant call to `Within`:
+
+```csharp
+[Test]
+public void RecordsEqualsMismatch()
+{
+    var a = new Data(1, 1.0);
+    var b = new Data(1, 1.1);
+
+    Assert.That(a, Is.EqualTo(b), $"{a} != {b}");
+}
+
+private sealed record Data(int number, double Value);
+```
+
+<!-- start generated config severity -->
+## Configure severity
+
+### Via ruleset file
+
+Configure the severity per project, for more info see [MSDN](https://learn.microsoft.com/en-us/visualstudio/code-quality/using-rule-sets-to-group-code-analysis-rules?view=vs-2022).
+
+### Via .editorconfig file
+
+```ini
+# NUnit2047: Incompatible types for Within constraint
+dotnet_diagnostic.NUnit2047.severity = chosenSeverity
+```
+
+where `chosenSeverity` can be one of `none`, `silent`, `suggestion`, `warning`, or `error`.
+
+### Via #pragma directive
+
+```csharp
+#pragma warning disable NUnit2047 // Incompatible types for Within constraint
+Code violating the rule here
+#pragma warning restore NUnit2047 // Incompatible types for Within constraint
+```
+
+Or put this at the top of the file to disable all instances.
+
+```csharp
+#pragma warning disable NUnit2047 // Incompatible types for Within constraint
+```
+
+### Via attribute `[SuppressMessage]`
+
+```csharp
+[System.Diagnostics.CodeAnalysis.SuppressMessage("Assertion",
+    "NUnit2047:Incompatible types for Within constraint",
+    Justification = "Reason...")]
+```
+<!-- end generated config severity -->

documentation/index.md

@@ -102,6 +102,7 @@ Rules which improve assertions in the test code.
 | [NUnit2044](https://github.com/nunit/nunit.analyzers/tree/master/documentation/NUnit2044.md) | Non-delegate actual parameter | :white_check_mark: | :exclamation: | :white_check_mark: |
 | [NUnit2045](https://github.com/nunit/nunit.analyzers/tree/master/documentation/NUnit2045.md) | Use Assert.Multiple | :white_check_mark: | :information_source: | :white_check_mark: |
 | [NUnit2046](https://github.com/nunit/nunit.analyzers/tree/master/documentation/NUnit2046.md) | Use CollectionConstraint for better assertion messages in case of failure | :white_check_mark: | :information_source: | :white_check_mark: |
+| [NUnit2047](https://github.com/nunit/nunit.analyzers/tree/master/documentation/NUnit2047.md) | Incompatible types for Within constraint | :white_check_mark: | :warning: | :white_check_mark: |
 
 ### Suppressor Rules (NUnit3001 - )
 

src/Directory.Build.props

@@ -24,6 +24,7 @@
     <PackageReference Include="StyleCop.Analyzers.Unstable" Version="1.2.0.435" PrivateAssets="all" />
     <PackageReference Include="Microsoft.CodeAnalysis.NetAnalyzers" Version="7.0.1" PrivateAssets="all" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp.CodeStyle" Version="3.11.0" PrivateAssets="all" />
+    <PackageReference Include="CSharpIsNullAnalyzer" Version="0.1.300" PrivateAssets="all" />
   </ItemGroup>
 
   <PropertyGroup>

src/nunit.analyzers.sln

@@ -88,6 +88,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "documentation", "documentat
 		..\documentation\NUnit2044.md = ..\documentation\NUnit2044.md
 		..\documentation\NUnit2045.md = ..\documentation\NUnit2045.md
 		..\documentation\NUnit2046.md = ..\documentation\NUnit2046.md
+		..\documentation\NUnit2047.md = ..\documentation\NUnit2047.md
 		..\documentation\NUnit3001.md = ..\documentation\NUnit3001.md
 		..\documentation\NUnit3002.md = ..\documentation\NUnit3002.md
 		..\README.md = ..\README.md