ReviewUnusedParameter.cs

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Management.Automation.Language;
using Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic;
#if !CORECLR
using System.ComponentModel.Composition;
#endif
using System.Globalization;

namespace Microsoft.Windows.PowerShell.ScriptAnalyzer.BuiltinRules
{
    /// <summary>
    /// ReviewUnusedParameter: Check that all declared parameters are used in the script body.
    /// </summary>
#if !CORECLR
[Export(typeof(IScriptRule))]
#endif
    public class ReviewUnusedParameter : IScriptRule
    {
        public IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string fileName)
        {
            if (ast == null)
            {
                throw new ArgumentNullException(Strings.NullAstErrorMessage);
            }

            IEnumerable<Ast> scriptBlockAsts = ast.FindAll(oneAst => oneAst is ScriptBlockAst, true);
            if (scriptBlockAsts == null)
            {
                yield break;
            }

            foreach (ScriptBlockAst scriptBlockAst in scriptBlockAsts)
            {
                // find all declared parameters
                IEnumerable<Ast> parameterAsts = scriptBlockAst.FindAll(oneAst => oneAst is ParameterAst, false);

                // list all variables
                IDictionary<string, int> variableCount = scriptBlockAst.FindAll(oneAst => oneAst is VariableExpressionAst, true)
                    .Select(variableExpressionAst => ((VariableExpressionAst)variableExpressionAst).VariablePath.UserPath)
                    .GroupBy(variableName => variableName, StringComparer.OrdinalIgnoreCase)
                    .ToDictionary(variableName => variableName.Key, variableName => variableName.Count(), StringComparer.OrdinalIgnoreCase);

                // all bets are off if the script uses PSBoundParameters
                if (variableCount.ContainsKey("PSBoundParameters"))
                {
                    continue;
                }

                foreach (ParameterAst parameterAst in parameterAsts)
                {
                    // there should be at least two usages of the variable since the parameter declaration counts as one
                    variableCount.TryGetValue(parameterAst.Name.VariablePath.UserPath, out int variableUsageCount);
                    if (variableUsageCount >= 2)
                    {
                        continue;
                    }

                    yield return new DiagnosticRecord(
                        string.Format(CultureInfo.CurrentCulture, Strings.ReviewUnusedParameterError, parameterAst.Name.VariablePath.UserPath),
                        parameterAst.Name.Extent,
                        GetName(),
                        DiagnosticSeverity.Warning,
                        fileName,
                        parameterAst.Name.VariablePath.UserPath
                    );
                }
            }
        }

        /// <summary>
        /// GetName: Retrieves the name of this rule.
        /// </summary>
        /// <returns>The name of this rule</returns>
        public string GetName()
        {
            return string.Format(CultureInfo.CurrentCulture, Strings.NameSpaceFormat, GetSourceName(), Strings.ReviewUnusedParameterName);
        }

        /// <summary>
        /// GetCommonName: Retrieves the common name of this rule.
        /// </summary>
        /// <returns>The common name of this rule</returns>
        public string GetCommonName()
        {
            return string.Format(CultureInfo.CurrentCulture, Strings.ReviewUnusedParameterCommonName);
        }

        /// <summary>
        /// GetDescription: Retrieves the description of this rule.
        /// </summary>
        /// <returns>The description of this rule</returns>
        public string GetDescription()
        {
            return string.Format(CultureInfo.CurrentCulture, Strings.ReviewUnusedParameterDescription);
        }

        /// <summary>
        /// GetSourceType: Retrieves the type of the rule, builtin, managed or module.
        /// </summary>
        public SourceType GetSourceType()
        {
            return SourceType.Builtin;
        }

        /// <summary>
        /// GetSeverity: Retrieves the severity of the rule: error, warning of information.
        /// </summary>
        /// <returns></returns>
        public RuleSeverity GetSeverity()
        {
            return RuleSeverity.Warning;
        }

        /// <summary>
        /// GetSourceName: Retrieves the module/assembly name the rule is from.
        /// </summary>
        public string GetSourceName()
        {
            return string.Format(CultureInfo.CurrentCulture, Strings.SourceName);
        }
    }
}