Code Inspections

A central feature of ReSharper and Rider is to show Code Inspections for potential quality issues, common practices and improvements, code redundancies, and other inspection categories. Such code inspections are further classified by severity levels, which determine how the code is underlined in the editor.

You can provide new code inspections by implementing:

IHighlighting – an interface containing all the necessary data to show code inspections (and to enable quick-fixes)
ElementProblemAnalyzer – a component that gets called by the SDK to analyze syntax trees and find highlightings

IHighlighting

The IHighlighting interface requires to implement 4 members, which return data specific to an individual occurrence of an inspection in code:

ToolTip and ErrorStripeToolTip are the strings that are shown while hovering the inspection in the editor or the stripes on the right-hand side of the editor
IsValid() determines whether the data connected with the inspection are still valid (usually PSI elements or text ranges)
CalculateRange() returns the range in the document where the inspection should be shown

Static and Configurable Severities

Independent of an individual IHighlighting instance, the SDK requires general information about the inspection type, which is provided through the StaticSeverityHighlightingAttribute or ConfigurableSeverityHighlightingAttribute. As the names suggest, one is for highlightings with static severities and the other to let users change them:

ConfigurableSeverityId is a unique inspection identifier used for severity configuration and suppression through comments
Languages defines the languages (C#, ...) for which the inspection is intended
OverlapResolve defines the policy when two inspections overlap
OverloadResolvePriority defines the priority when two inspections with the same overlap policy and range collide

If you've applied the ConfigurableSeverityHighlightingAttribute, you also need to add the RegisterConfigurableSeverity with the following information:

Group should reference a well-known identifier from HighlightingGroupIds (but you can also define your own group)
DefaultSeverity is the pre-configured severity level of the inspection
Title* represents the searchable title and is shown in the list of all inspections
Description* is shown in the bottom field when the inspection is selected

ElementProblemAnalyzer

The ElementProblemAnalyzer<T> component is responsible to examine all syntax trees in the solution and to create highlightings accordingly. The generic parameter T is used to constrain the elements on which the analyzer should run, e.g., with ICSharpDeclaration, it is only called for types and members. The Run is invoked by the SDK with the following parameters:

T element is the start element from where the syntax tree is analyzed
ElementProblemAnalyzerData provides additional context about the analysis
- Solution and File for the analyzed element
- SettingsStore for checking settings that influence the highlighting (except severity)
- ThrowIfInterrupted() should be called in more complex analyzers
IHighlightingConsumer is used to pass created highlightings out of the analyzer, usually AddHighlighting

To allow the SDK working with the analyzer, it must be marked with the ElementProblemAnalyzerAttribute and include the following information:

ElementTypes are the ITreeNode abstractions on which the analyzer is called; usually this is the same as T, but an analyzer can also implement the non-generic IElementProblemAnalyzer
HighlightingTypes enumerates all highlighting types that are generated by the analyzer

Sample Implementation

Highlighting

[RegisterConfigurableSeverity(
    SeverityId,
    CompoundItemName: null,
    Group: HighlightingGroupIds.CodeSmell,
    Title: Message,
    Description: Description,
    DefaultSeverity: Severity.WARNING)]
[ConfigurableSeverityHighlighting(
    SeverityId,
    CSharpLanguage.Name,
    OverlapResolve = OverlapResolveKind.ERROR,
    OverloadResolvePriority = 0,
    // Appears in solution-wide analysis
    ToolTipFormatString = Message)]
public class SampleDeclarationHighlighting : IHighlighting
{
    // Appears in suppression comments
    public const string SeverityId = "SampleDeclarationInspection";

    // Appears in settings
    public const string Message = $"ReSharper SDK: {nameof(SampleDeclarationHighlighting)}.{nameof(Message)}";
    public const string Description = $"ReSharper SDK: {nameof(SampleDeclarationHighlighting)}.{nameof(Description)}";

    public SampleDeclarationHighlighting(ICSharpDeclaration declaration)
    {
        Declaration = declaration;
    }

    // Used for IsValid and quick-fixes
    public ICSharpDeclaration Declaration { get; }

    public bool IsValid() => Declaration.IsValid();
    public DocumentRange CalculateRange() => Declaration.NameIdentifier.NotNull().GetHighlightingRange();

    // Appears in editor
    public string ToolTip => $"ReSharper SDK: {nameof(SampleDeclarationHighlighting)}.{nameof(Message)}";

    // Appears in scrollbar
    public string ErrorStripeToolTip => $"ReSharper SDK: {nameof(SampleDeclarationHighlighting)}.{nameof(ErrorStripeToolTip)}";
}

ProblemAnalyzer

[ElementProblemAnalyzer(
    typeof(ICSharpDeclaration),
    // Allows to disable the problem analyzer if code inspection is disabled
    HighlightingTypes = new[] { typeof(SampleDeclarationHighlighting) })]
public class SampleDeclarationProblemAnalyzer : ElementProblemAnalyzer<ICSharpDeclaration>
{
    protected override void Run(
        ICSharpDeclaration element,
        ElementProblemAnalyzerData data,
        IHighlightingConsumer consumer)
    {
        if (element.NameIdentifier?.Name.All(char.IsUpper) ?? true)
            return;

        consumer.AddHighlighting(new SampleDeclarationHighlighting(element));
    }
}

Last modified: 04 July 2023