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Added Rule UseSingleValueFromPipelineParameter
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‎Rules/Strings.resx‎

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<data name="AvoidReservedWordsAsFunctionNamesError" xml:space="preserve">
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<value>The reserved word '{0}' was used as a function name. This should be avoided.</value>
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</data>
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<data name="UseSingleValueFromPipelineParameterCommonName" xml:space="preserve">
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<value>Use a single ValueFromPipeline parameter per parameter set</value>
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</data>
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<data name="UseSingleValueFromPipelineParameterDescription" xml:space="preserve">
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<value>Use at most a single ValueFromPipeline parameter per parameter set to avoid undefined or unexpected behaviour.</value>
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</data>
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<data name="UseSingleValueFromPipelineParameterError" xml:space="preserve">
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<value>Multiple parameters ({0}) in parameter set '{1}' are marked as ValueFromPipeline. Only one parameter per parameter set should accept pipeline input.</value>
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</data>
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<data name="UseSingleValueFromPipelineParameterName" xml:space="preserve">
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<value>UseSingleValueFromPipelineParameter</value>
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</data>
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</root>

‎Rules/UseSingleValueFromPipelineParameter.cs‎

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// Copyright (c) Microsoft Corporation. All rights reserved.
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// Licensed under the MIT License.
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using Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic;
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using System;
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using System.Collections.Generic;
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using System.Globalization;
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using System.Linq;
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using System.Management.Automation.Language;
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#if !CORECLR
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using System.ComponentModel.Composition;
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#endif
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namespace Microsoft.Windows.PowerShell.ScriptAnalyzer.BuiltinRules
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{
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#if !CORECLR
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[Export(typeof(IScriptRule))]
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#endif
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/// <summary>
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/// Rule that identifies parameter blocks with multiple parameters in
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/// the same parameter set that are marked as ValueFromPipeline=true, which
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/// can cause undefined behavior.
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/// </summary>
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public class UseSingleValueFromPipelineParameter : IScriptRule
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{
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private const string AllParameterSetsName = "__AllParameterSets";
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/// <summary>
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/// Analyzes the PowerShell AST for parameter sets with multiple ValueFromPipeline parameters.
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/// </summary>
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/// <param name="ast">The PowerShell Abstract Syntax Tree to analyze.</param>
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/// <param name="fileName">The name of the file being analyzed (for diagnostic reporting).</param>
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/// <returns>A collection of diagnostic records for each violating parameter.</returns>
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public IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string fileName)
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{
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if (ast == null)
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{
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yield break;
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}
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// Find all param blocks that have a Parameter attribute with
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// ValueFromPipeline set to true.
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var paramBlocks = ast.FindAll(testAst => testAst is ParamBlockAst, true)
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.Where(paramBlock => paramBlock.FindAll(
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attributeAst => attributeAst is AttributeAst attr &&
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ParameterAttributeAstHasValueFromPipeline(attr),
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true
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).Any());
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foreach (var paramBlock in paramBlocks)
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{
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// Find all parameter declarations in the current param block
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// Convert the generic ast objects into ParameterAst Objects
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// For each ParameterAst, find all it's attributes that have
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// ValueFromPipeline set to true (either explicitly or
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// implicitly). Flatten the results into a single collection of
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// Annonymous objects relating the parameter with it's attribute
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// and then group them by parameter set name.
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//
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//
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// https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_parameter_sets?#reserved-parameter-set-name
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//
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// The default parameter set name is '__AllParameterSets'.
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// Not specifying a parameter set name and using the parameter
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// set name '__AllParameterSets' are equivalent, so we shouldn't
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// treat them like they're different just because one is an
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// empty string and the other is not.
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//
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// Filter the list to only keep parameter sets that have more
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// than one ValueFromPipeline parameter.
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var parameterSetGroups = paramBlock.FindAll(n => n is ParameterAst, true)
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.Cast<ParameterAst>()
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.SelectMany(parameter => parameter.FindAll(
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a => a is AttributeAst attr && ParameterAttributeAstHasValueFromPipeline(attr),
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true
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).Cast<AttributeAst>().Select(attr => new { Parameter = parameter, Attribute = attr }))
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.GroupBy(item => GetParameterSetForAttribute(item.Attribute) ?? AllParameterSetsName)
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.Where(group => group.Count() > 1);
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foreach (var group in parameterSetGroups)
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{
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// __AllParameterSets being the default name is...obscure.
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// Instead we'll show the user "default". It's more than
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// likely the user has not specified a parameter set name,
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// so default will make sense. If they have used 'default'
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// as their parameter set name, then we're still correct.
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var parameterSetName = group.Key == AllParameterSetsName ? "default" : group.Key;
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// Create a concatenated string of parameter names that
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// conflict in this parameter set
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var parameterNames = string.Join(", ", group.Select(item => item.Parameter.Name.VariablePath.UserPath));
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// We emit a diagnostic record for each offending parameter
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// attribute in the parameter set so it's obvious where all the
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// occurrences are.
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foreach (var item in group)
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{
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var message = string.Format(CultureInfo.CurrentCulture,
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Strings.UseSingleValueFromPipelineParameterError,
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parameterNames,
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parameterSetName);
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yield return new DiagnosticRecord(
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message,
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item.Attribute.Extent,
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GetName(),
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DiagnosticSeverity.Warning,
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fileName,
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parameterSetName);
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}
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}
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}
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}
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/// <summary>
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/// Returns whether the specified AttributeAst represents a Parameter attribute
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/// that has the ValueFromPipeline named argument set to true (either explicitly or
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/// implicitly).
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/// </summary>
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/// <param name="attributeAst">The Parameter attribute to examine.</param>
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/// <returns>Whether the attribute has the ValueFromPipeline named argument set to true.</returns>
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private static bool ParameterAttributeAstHasValueFromPipeline(AttributeAst attributeAst)
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{
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// Exit quickly if the attribute is null, has no named arguments, or
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// is not a parameter attribute.
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if (attributeAst?.NamedArguments == null ||
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!string.Equals(attributeAst.TypeName?.Name, "Parameter", StringComparison.OrdinalIgnoreCase))
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{
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return false;
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}
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return attributeAst.NamedArguments
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.OfType<NamedAttributeArgumentAst>()
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.Any(namedArg => string.Equals(
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namedArg?.ArgumentName,
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"ValueFromPipeline",
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StringComparison.OrdinalIgnoreCase
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// Helper.Instance.GetNamedArgumentAttributeValue handles both explicit ($true)
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// and implicit (no value specified) ValueFromPipeline declarations
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) && Helper.Instance.GetNamedArgumentAttributeValue(namedArg));
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}
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/// <summary>
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/// Gets the ParameterSetName value from a Parameter attribute.
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/// </summary>
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/// <param name="attributeAst">The Parameter attribute to examine.</param>
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/// <returns>The parameter set name, or null if not found or empty.</returns>
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private static string GetParameterSetForAttribute(AttributeAst attributeAst)
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{
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// Exit quickly if the attribute is null, has no named arguments, or
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// is not a parameter attribute.
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if (attributeAst?.NamedArguments == null ||
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!string.Equals(attributeAst.TypeName.Name, "Parameter", StringComparison.OrdinalIgnoreCase))
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{
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return null;
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}
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return attributeAst.NamedArguments
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.OfType<NamedAttributeArgumentAst>()
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.Where(namedArg => string.Equals(
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namedArg?.ArgumentName,
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"ParameterSetName",
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StringComparison.OrdinalIgnoreCase
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))
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.Select(namedArg => namedArg?.Argument)
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.OfType<StringConstantExpressionAst>()
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.Select(stringConstAst => stringConstAst?.Value)
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.FirstOrDefault(value => !string.IsNullOrWhiteSpace(value));
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}
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public string GetCommonName() => Strings.UseSingleValueFromPipelineParameterCommonName;
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public string GetDescription() => Strings.UseSingleValueFromPipelineParameterDescription;
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public string GetName() => Strings.UseSingleValueFromPipelineParameterName;
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public RuleSeverity GetSeverity() => RuleSeverity.Warning;
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public string GetSourceName() => Strings.SourceName;
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public SourceType GetSourceType() => SourceType.Builtin;
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}
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}

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