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Merge pull request #850 from polyadic/list-pattern-analyzer
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‎Funcky.Analyzers/Funcky.Analyzers.Test/OptionListPatternTest.cs

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using Microsoft.CodeAnalysis.Testing;
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using Xunit;
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using VerifyCS = Funcky.Analyzers.Test.CSharpAnalyzerVerifier<Funcky.Analyzers.OptionListPatternAnalyzer>;
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namespace Funcky.Analyzers.Test;
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public sealed class OptionListPatternTest
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{
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// language=csharp
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private const string OptionStub =
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"""
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namespace Funcky.Monads
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{
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public readonly struct Option<T>
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{
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public int Count => throw null!;
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public T this[int index] => throw null!;
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}
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}
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""";
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[Fact]
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public async Task ErrorsWhenListPatternHasMoreThanOneElement()
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{
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// language=csharp
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const string inputCode =
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"""
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using Funcky.Monads;
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class C
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{
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private void M(Option<string> option)
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{
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_ = option is ["foo", "bar"];
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_ = option is [var foo, var bar, var baz];
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_ = option is [var one, var two, var three, var four];
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}
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}
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""";
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DiagnosticResult[] expectedDiagnostics = [
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VerifyCS.Diagnostic().WithSpan(7, 23, 7, 37),
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VerifyCS.Diagnostic().WithSpan(8, 23, 8, 50),
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VerifyCS.Diagnostic().WithSpan(9, 23, 9, 62),
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];
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await VerifyCS.VerifyAnalyzerAsync(inputCode + Environment.NewLine + OptionStub, expectedDiagnostics);
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}
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[Fact]
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public async Task DoesNotErrorWhenUsingAListPatternWithZeroOrOneElements()
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{
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// language=csharp
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const string inputCode =
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"""
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using Funcky.Monads;
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class C
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{
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private void M(Option<string> option)
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{
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_ = option is ["foo"];
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_ = option is [];
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}
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}
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""";
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await VerifyCS.VerifyAnalyzerAsync(inputCode + Environment.NewLine + OptionStub);
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}
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[Fact]
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public async Task UsingASlicePatternIsACompileError()
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{
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// language=csharp
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const string inputCode =
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"""
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using Funcky.Monads;
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class C
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{
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private void M(Option<string> option)
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{
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_ = option is [..var slice];
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}
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}
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""";
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DiagnosticResult[] expectedDiagnostics = [
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DiagnosticResult.CompilerError("CS1503").WithSpan(7, 24, 7, 35).WithArguments("1", "System.Range", "int"),
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];
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await VerifyCS.VerifyAnalyzerAsync(inputCode + Environment.NewLine + OptionStub, expectedDiagnostics);
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}
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}

‎Funcky.Analyzers/Funcky.Analyzers/AnalyzerReleases.Unshipped.md

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### New Rules
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Rule ID | Category | Severity | Notes
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--------|----------|----------|-------
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λ1010 | Funcky | Error | OptionListPatternAnalyzer
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λ1101 | Funcky | Warning | FunctionalAssertAnalyzer

‎Funcky.Analyzers/Funcky.Analyzers/Funcky.Analyzers.Roslyn4.0.csproj

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<AnalyzerRoslynVersion>4.0.1</AnalyzerRoslynVersion>
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<DisableAnalyzerReleaseTracking>true</DisableAnalyzerReleaseTracking>
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</PropertyGroup>
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<Import Project="Funcky.Analyzers.targets" />
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</Project>

‎Funcky.Analyzers/Funcky.Analyzers/Funcky.Analyzers.targets

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<ItemGroup>
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<EmbeddedResource Update="Resources.resx" Generator="ResXFileCodeGenerator" LastGenOutput="Resources.Designer.cs" />
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</ItemGroup>
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<PropertyGroup Condition="'$(DisableAnalyzerReleaseTracking)' == 'true'">
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<!-- RS2008: Enable analyzer release tracking -->
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<NoWarn>$(NoWarn);RS2008</NoWarn>
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</PropertyGroup>
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<Target Name="_FunckyRemoveAnalyzerReleasesFiles" BeforeTargets="CoreCompile" Condition="'$(DisableAnalyzerReleaseTracking)' == 'true'">
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<ItemGroup>
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<AdditionalFiles Remove="AnalyzerReleases.Shipped.md" />
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<AdditionalFiles Remove="AnalyzerReleases.Unshipped.md" />
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</ItemGroup>
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</Target>
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<Import Project="..\Funcky.Analyzers.Package\Packing.targets" />
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</Project>

‎Funcky.Analyzers/Funcky.Analyzers/OptionListPatternAnalyzer.cs

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#if ROSLYN_4_4_0
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using System.Collections.Immutable;
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using Microsoft.CodeAnalysis;
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using Microsoft.CodeAnalysis.Diagnostics;
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using Microsoft.CodeAnalysis.Operations;
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namespace Funcky.Analyzers;
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[DiagnosticAnalyzer(LanguageNames.CSharp)]
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public sealed class OptionListPatternAnalyzer : DiagnosticAnalyzer
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{
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public static readonly DiagnosticDescriptor OptionHasZeroOrOneElements = new(
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id: $"{DiagnosticName.Prefix}{DiagnosticName.Usage}10",
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title: "An option has either zero or one elements",
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messageFormat: "An option has either zero or one elements, testing for more elements will never match",
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category: nameof(Funcky),
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DiagnosticSeverity.Error,
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isEnabledByDefault: true);
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public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => ImmutableArray.Create(OptionHasZeroOrOneElements);
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public override void Initialize(AnalysisContext context)
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{
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context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
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context.EnableConcurrentExecution();
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context.RegisterCompilationStartAction(OnCompilationStart);
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}
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private static void OnCompilationStart(CompilationStartAnalysisContext context)
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{
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if (context.Compilation.GetOptionOfTType() is { } optionOfTType)
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{
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context.RegisterOperationAction(AnalyzeListPattern(optionOfTType), OperationKind.ListPattern);
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}
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}
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private static Action<OperationAnalysisContext> AnalyzeListPattern(INamedTypeSymbol optionOfTType)
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=> context
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=>
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{
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var operation = (IListPatternOperation)context.Operation;
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if (SymbolEqualityComparer.Default.Equals(operation.InputType.OriginalDefinition, optionOfTType)
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&& operation.Patterns.Length > 1)
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{
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context.ReportDiagnostic(Diagnostic.Create(OptionHasZeroOrOneElements, operation.Syntax.GetLocation()));
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}
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};
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}
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#endif

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