ScriptAnalyzer.cs

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

using System.Text.RegularExpressions;
using Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic;
using System;
using System.Collections.Generic;
#if !CORECLR
using System.ComponentModel.Composition;
using System.ComponentModel.Composition.Hosting;
#endif // !CORECLR
using System.IO;
using System.Linq;
using System.Management.Automation;
using System.Management.Automation.Language;
using System.Management.Automation.Runspaces;
using System.Reflection;
using System.Globalization;
using System.Collections.Concurrent;
using System.Threading.Tasks;
using System.Collections.ObjectModel;
using System.Collections;
using System.Diagnostics;
using System.Text;

namespace Microsoft.Windows.PowerShell.ScriptAnalyzer
{
    public sealed class ScriptAnalyzer
    {
        #region Private members

        private IOutputWriter outputWriter;
        private Dictionary<string, object> settings;
#if !CORECLR
        private CompositionContainer container;
#endif // !CORECLR
        Dictionary<string, List<string>> validationResults = new Dictionary<string, List<string>>();
        string[] includeRule;
        string[] excludeRule;
        string[] severity;
        List<Regex> includeRegexList;
        List<Regex> excludeRegexList;
        bool suppressedOnly;
#if !PSV3
        ModuleDependencyHandler moduleHandler;
#endif
#endregion

#region Singleton
        private static object syncRoot = new Object();
        private static ScriptAnalyzer instance;
        public static ScriptAnalyzer Instance
        {
            get
            {
                if (instance == null)
                {
                    lock (syncRoot)
                    {
                        if (instance == null)
                            instance = new ScriptAnalyzer();
                    }
                }

                return instance;
            }
        }

        #endregion

        #region Properties

#if CORECLR
        public IEnumerable<IScriptRule> ScriptRules { get; private set; }
        public IEnumerable<ITokenRule> TokenRules { get; private set; }
        public IEnumerable<ILogger> Loggers { get; private set; }
        public IEnumerable<IDSCResourceRule> DSCResourceRules { get; private set; }
#else
        [ImportMany]
        public IEnumerable<IScriptRule> ScriptRules { get; private set; }
        [ImportMany]
        public IEnumerable<ITokenRule> TokenRules { get; private set; }
        [ImportMany]
        public IEnumerable<ILogger> Loggers { get; private set; }
        [ImportMany]
        public IEnumerable<IDSCResourceRule> DSCResourceRules { get; private set; }
        // Initializes via ImportMany
#endif // !CORECLR

        internal List<ExternalRule> ExternalRules { get; set; }

#if !PSV3
        public ModuleDependencyHandler ModuleHandler {
            get
            {
                return moduleHandler;
            }

            internal set
            {
                moduleHandler = value;
            }
        }
#endif

#endregion

#region Methods

        /// <summary>
        /// Initialize : Initializes default rules, loggers and helper.
        /// </summary>
        internal void Initialize<TCmdlet>(
            TCmdlet cmdlet,
            string[] customizedRulePath = null,
            string[] includeRuleNames = null,
            string[] excludeRuleNames = null,
            string[] severity = null,
            bool includeDefaultRules = false,
            bool suppressedOnly = false)
            where TCmdlet : PSCmdlet, IOutputWriter
        {
            if (cmdlet == null)
            {
                throw new ArgumentNullException("cmdlet");
            }

            this.Initialize(
                cmdlet,
                cmdlet.SessionState.Path,
                cmdlet.SessionState.InvokeCommand,
                customizedRulePath,
                includeRuleNames,
                excludeRuleNames,
                severity,
                includeDefaultRules,
                suppressedOnly);
        }

        /// <summary>
        /// Initialize : Initializes default rules, loggers and helper.
        /// </summary>
        public void Initialize(
            Runspace runspace,
            IOutputWriter outputWriter,
            string[] customizedRulePath = null,
            string[] includeRuleNames = null,
            string[] excludeRuleNames = null,
            string[] severity = null,
            bool includeDefaultRules = false,
            bool suppressedOnly = false,
            string profile = null)
        {
            if (runspace == null)
            {
                throw new ArgumentNullException("runspace");
            }

            //initialize helper
            Helper.Instance = new Helper(
                runspace.SessionStateProxy.InvokeCommand,
                outputWriter);
            Helper.Instance.Initialize();


            this.Initialize(
                outputWriter,
                runspace.SessionStateProxy.Path,
                runspace.SessionStateProxy.InvokeCommand,
                customizedRulePath,
                includeRuleNames,
                excludeRuleNames,
                severity,
                includeDefaultRules,
                suppressedOnly,
                profile);
        }

        /// <summary>
        /// clean up this instance, resetting all properties
        /// </summary>
        public void CleanUp()
        {
            includeRule = null;
            excludeRule = null;
            severity = null;
            includeRegexList = null;
            excludeRegexList = null;
            suppressedOnly = false;
        }

        /// <summary>
        /// Update includerules, excluderules, severity and rule arguments.
        /// </summary>
        /// <param name="settings">An object of type Settings</param>
        public void UpdateSettings(Settings settings)
        {
            if (settings == null)
            {
                throw new ArgumentNullException(nameof(settings));
            }

            this.severity = (!settings.Severities.Any()) ? null : settings.Severities.ToArray();
            this.includeRule = (!settings.IncludeRules.Any()) ? null : settings.IncludeRules.ToArray();
            this.excludeRule = (!settings.ExcludeRules.Any()) ? null : settings.ExcludeRules.ToArray();
            if (settings.RuleArguments != null)
            {
                Helper.Instance.SetRuleArguments(
                    settings.RuleArguments.ToDictionary(
                        kvp => kvp.Key,
                        kvp => kvp.Value as object,
                        StringComparer.OrdinalIgnoreCase));
            }
        }

        internal bool ParseProfile(object profileObject, PathIntrinsics path, IOutputWriter writer)
        {
            // profile was not given
            if (profileObject == null)
            {
                writer.WriteVerbose("No settings hashtable or file to consume");
                return true;
            }

            if (!(profileObject is string || profileObject is Hashtable))
            {
                writer.WriteWarning("Settings parameter should be a hashtable or a filepath");
                return false;
            }

            List<string> includeRuleList = new List<string>();
            List<string> excludeRuleList = new List<string>();
            List<string> severityList = new List<string>();

            bool hasError = false;

            Hashtable hashTableProfile = profileObject as Hashtable;

            // checks whether we get a hashtable
            if (hashTableProfile != null)
            {
                hasError = ParseProfileHashtable(hashTableProfile, path, writer, severityList, includeRuleList, excludeRuleList);
            }
            else
            {
                // checks whether we get a string instead
                string profile = profileObject as string;

                if (!String.IsNullOrWhiteSpace(profile))
                {
                    hasError = ParseProfileString(profile, path, writer, severityList, includeRuleList, excludeRuleList);
                }
            }

            if (hasError)
            {
                return false;
            }

            this.severity = (severityList.Count() == 0) ? null : severityList.ToArray();
            this.includeRule = (includeRuleList.Count() == 0) ? null : includeRuleList.ToArray();
            this.excludeRule = (excludeRuleList.Count() == 0) ? null : excludeRuleList.ToArray();
            if (settings != null
                && settings.ContainsKey("Rules"))
            {
                var ruleArgs = settings["Rules"] as Dictionary<string, object>;
                Helper.Instance.SetRuleArguments(ruleArgs);
            }
            return true;
        }

        private bool AddProfileItem(
            string key,
            List<string> values,
            List<string> severityList,
            List<string> includeRuleList,
            List<string> excludeRuleList)
        {
            Debug.Assert(key != null);
            Debug.Assert(values != null);
            Debug.Assert(severityList != null);
            Debug.Assert(includeRuleList != null);
            Debug.Assert(excludeRuleList != null);

            switch (key.ToLower())
            {
                case "severity":
                    severityList.AddRange(values);
                    break;
                case "includerules":
                    includeRuleList.AddRange(values);
                    break;
                case "excluderules":
                    excludeRuleList.AddRange(values);
                    break;
                default:
                    return false;
            }
            return true;
        }

        private Dictionary<string, object> GetDictionaryFromHashTableAst(
            HashtableAst hashTableAst,
            IOutputWriter writer,
            string profile,
            out bool hasError)
        {
            hasError = false;
            var output = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
            foreach (var kvp in hashTableAst.KeyValuePairs)
            {
                var keyAst = kvp.Item1 as StringConstantExpressionAst;
                if (keyAst == null)
                {
                    // first item (the key) should be a string
                    writer.WriteError(
                        new ErrorRecord(
                            new InvalidDataException(
                                string.Format(
                                    CultureInfo.CurrentCulture,
                                    Strings.WrongKeyFormat,
                                    kvp.Item1.Extent.StartLineNumber,
                                    kvp.Item1.Extent.StartColumnNumber,
                                    profile)),
                            Strings.ConfigurationKeyNotAString,
                            ErrorCategory.InvalidData,
                            profile));
                    hasError = true;
                    continue;
                }
                var key = keyAst.Value;
                // parse the item2 as array
                PipelineAst pipeAst = kvp.Item2 as PipelineAst;
                List<string> rhsList = new List<string>();
                if (pipeAst != null)
                {
                    ExpressionAst pureExp = pipeAst.GetPureExpression();
                    if (pureExp is StringConstantExpressionAst)
                    {
                        rhsList.Add((pureExp as StringConstantExpressionAst).Value);
                    }
                    else if (pureExp is HashtableAst)
                    {
                        output[key] = GetDictionaryFromHashTableAst(
                            pureExp as HashtableAst,
                            writer,
                            profile,
                            out hasError);
                        continue;
                    }
                    else
                    {
                        ArrayLiteralAst arrayLitAst = pureExp as ArrayLiteralAst;
                        if (arrayLitAst == null && pureExp is ArrayExpressionAst)
                        {
                            ArrayExpressionAst arrayExp = pureExp as ArrayExpressionAst;
                            // Statements property is never null
                            if (arrayExp.SubExpression != null)
                            {
                                StatementAst stateAst = arrayExp.SubExpression.Statements.FirstOrDefault();
                                if (stateAst != null && stateAst is PipelineAst)
                                {
                                    CommandBaseAst cmdBaseAst = (stateAst as PipelineAst).PipelineElements.FirstOrDefault();
                                    if (cmdBaseAst != null && cmdBaseAst is CommandExpressionAst)
                                    {
                                        CommandExpressionAst cmdExpAst = cmdBaseAst as CommandExpressionAst;
                                        if (cmdExpAst.Expression is StringConstantExpressionAst)
                                        {
                                            rhsList.Add((cmdExpAst.Expression as StringConstantExpressionAst).Value);
                                        }
                                        else
                                        {
                                            arrayLitAst = cmdExpAst.Expression as ArrayLiteralAst;
                                        }
                                    }
                                }
                            }
                        }

                        if (arrayLitAst != null)
                        {
                            foreach (var element in arrayLitAst.Elements)
                            {
                                // all the values in the array needs to be string
                                if (!(element is StringConstantExpressionAst))
                                {
                                    outputWriter.WriteError(
                                        new ErrorRecord(
                                            new InvalidDataException(
                                                string.Format(
                                                    CultureInfo.CurrentCulture,
                                                    Strings.WrongValueFormat,
                                                    element.Extent.StartLineNumber,
                                                    element.Extent.StartColumnNumber,
                                                    "")),
                                        Strings.ConfigurationValueNotAString,
                                        ErrorCategory.InvalidData,
                                        null));
                                    hasError = true;
                                    continue;
                                }

                                rhsList.Add((element as StringConstantExpressionAst).Value);
                            }
                        }
                    }
                }

                if (rhsList.Count == 0)
                {
                    writer.WriteError(
                        new ErrorRecord(
                            new InvalidDataException(
                                string.Format(
                                    CultureInfo.CurrentCulture,
                                    Strings.WrongValueFormat,
                                    kvp.Item2.Extent.StartLineNumber,
                                    kvp.Item2.Extent.StartColumnNumber,
                                    profile)),
                            Strings.ConfigurationValueWrongFormat,
                            ErrorCategory.InvalidData,
                            profile));
                    hasError = true;
                    continue;
                }
                output[key] = rhsList;
            }
            return output;
        }

        /// <summary>
        /// Recursively convert hashtable to dictionary
        /// </summary>
        /// <param name="hashtable"></param>
        /// <returns>Dictionary that maps string to object</returns>
        private Dictionary<string, object> GetDictionaryFromHashtable(
            Hashtable hashtable,
            IOutputWriter writer,
            out bool hasError)
        {
            var dictionary = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
            hasError = false;
            foreach (var obj in hashtable.Keys)
            {
                string key = obj as string;
                if (key == null)
                {
                    writer.WriteError(
                        new ErrorRecord(
                            new InvalidDataException(string.Format(CultureInfo.CurrentCulture, Strings.KeyNotString, key)),
                            Strings.ConfigurationKeyNotAString,
                            ErrorCategory.InvalidData,
                            hashtable));
                    hasError = true;
                    return null;
                }
                var valueHashtableObj = hashtable[obj];
                if (valueHashtableObj == null)
                {
                    writer.WriteError(
                        new ErrorRecord(
                            new InvalidDataException(string.Format(CultureInfo.CurrentCulture, Strings.WrongValueHashTable, valueHashtableObj, key)),
                            Strings.WrongConfigurationKey,
                            ErrorCategory.InvalidData,
                            hashtable));
                    hasError = true;
                    return null;
                }
                var valueHashtable = valueHashtableObj as Hashtable;
                if (valueHashtable == null)
                {
                    dictionary.Add(key, valueHashtableObj);
                }
                else
                {
                    var dict = GetDictionaryFromHashtable(valueHashtable, writer, out hasError);
                    if (dict != null)
                    {
                        dictionary.Add(key, dict);
                    }
                    else
                    {
                        return null;
                    }
                }

            }
            return dictionary;
        }

        private bool ParseProfileHashtable(Hashtable profile, PathIntrinsics path, IOutputWriter writer,
            List<string> severityList, List<string> includeRuleList, List<string> excludeRuleList)
        {
            bool hasError = false;

            HashSet<string> validKeys = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
            validKeys.Add("severity");
            validKeys.Add("includerules");
            validKeys.Add("excluderules");
            validKeys.Add("rules");

            settings = GetDictionaryFromHashtable(profile, writer, out hasError);
            if (hasError)
            {
                return hasError;
            }

            var settingsKeys = new string[settings.Keys.Count];
            settings.Keys.CopyTo(settingsKeys, 0);
            foreach (var settingKey in settingsKeys)
            {
                var key = settingKey.ToLower();
                object value = settings[key];
                switch (key)
                {
                    case "severity":
                    case "includerules":
                    case "excluderules":
                        // value must be either string or collections of string or array
                        if (value == null
                            || !(value is string
                                || value is IEnumerable<string>
                                || value.GetType().IsArray))
                        {
                            writer.WriteError(
                                new ErrorRecord(
                                    new InvalidDataException(string.Format(CultureInfo.CurrentCulture, Strings.WrongValueHashTable, value, key)),
                                    Strings.WrongConfigurationKey,
                                    ErrorCategory.InvalidData,
                                    profile));
                            hasError = true;
                            break;
                        }
                        List<string> values = new List<string>();
                        if (value is string)
                        {
                            values.Add(value as string);
                        }
                        else if (value is IEnumerable<string>)
                        {
                            values.Union(value as IEnumerable<string>);
                        }
                        else if (value.GetType().IsArray)
                        {
                            // for array case, sometimes we won't be able to cast it directly to IEnumerable<string>
                            foreach (var val in value as IEnumerable)
                            {
                                if (val is string)
                                {
                                    values.Add(val as string);
                                }
                                else
                                {
                                    writer.WriteError(
                                        new ErrorRecord(
                                            new InvalidDataException(string.Format(CultureInfo.CurrentCulture, Strings.WrongValueHashTable, val, key)),
                                            Strings.WrongConfigurationKey,
                                            ErrorCategory.InvalidData,
                                            profile));
                                    hasError = true;
                                    break;
                                }
                            }
                        }
                        AddProfileItem(key, values, severityList, includeRuleList, excludeRuleList);
                        settings[key] = values;
                        break;

                    case "rules":
                        break;

                    default:
                        writer.WriteError(
                            new ErrorRecord(
                                new InvalidDataException(string.Format(CultureInfo.CurrentCulture, Strings.WrongKeyHashTable, key)),
                                Strings.WrongConfigurationKey,
                                ErrorCategory.InvalidData,
                                profile));
                        hasError = true;
                        break;
                }
            }
            return hasError;
        }

        private bool ParseProfileString(string profile, PathIntrinsics path, IOutputWriter writer,
            List<string> severityList, List<string> includeRuleList, List<string> excludeRuleList)
        {
            bool hasError = false;

            try
            {
                profile = path.GetResolvedPSPathFromPSPath(profile).First().Path;
            }
            catch
            {
                writer.WriteError(new ErrorRecord(new FileNotFoundException(string.Format(CultureInfo.CurrentCulture, Strings.FileNotFound, profile)),
                    Strings.ConfigurationFileNotFound, ErrorCategory.ResourceUnavailable, profile));
                hasError = true;
            }

            if (File.Exists(profile))
            {
                Token[] parserTokens = null;
                ParseError[] parserErrors = null;
                Ast profileAst = Parser.ParseFile(profile, out parserTokens, out parserErrors);
                IEnumerable<Ast> hashTableAsts = profileAst.FindAll(item => item is HashtableAst, false);

                // no hashtable, raise warning
                if (hashTableAsts.Count() == 0)
                {
                    writer.WriteError(new ErrorRecord(new ArgumentException(string.Format(CultureInfo.CurrentCulture, Strings.InvalidProfile, profile)),
                        Strings.ConfigurationFileHasNoHashTable, ErrorCategory.ResourceUnavailable, profile));
                    hasError = true;
                }
                else
                {
                    HashtableAst hashTableAst = hashTableAsts.First() as HashtableAst;
#if PSV3
                    settings = GetDictionaryFromHashTableAst(
                        hashTableAst,
                        writer,
                        profile,
                        out hasError);
                    foreach (var key in settings.Keys)
                    {
                        var rhsList = settings[key] as List<string>;
                        if (rhsList == null)
                        {
                            continue;
                        }
                        if (!AddProfileItem(key, rhsList, severityList, includeRuleList, excludeRuleList))
                        {
                            writer.WriteError(
                                new ErrorRecord(
                                    new InvalidDataException(
                                        string.Format(
                                            CultureInfo.CurrentCulture,
                                            Strings.WrongKey,
                                            key,
                                            profile)),
                                    Strings.WrongConfigurationKey,
                                    ErrorCategory.InvalidData,
                                    profile));
                            hasError = true;
                        }
                    }
#else

                    try
                    {
                        var hashtable = hashTableAst.SafeGetValue() as Hashtable;
                        hasError = ParseProfileHashtable(hashtable, path, writer, severityList, includeRuleList, excludeRuleList);
                    }
                    catch
                    {
                        writer.WriteError(
                            new ErrorRecord(
                                new ArgumentException(string.Format(CultureInfo.CurrentCulture, Strings.InvalidProfile, profile)),
                                Strings.ConfigurationFileHasInvalidHashtable,
                                ErrorCategory.ResourceUnavailable,
                                profile));
                        hasError = true;
                    }
#endif // PSV3
                }
            }

            return hasError;
        }

        private void Initialize(
            IOutputWriter outputWriter,
            PathIntrinsics path,
            CommandInvocationIntrinsics invokeCommand,
            string[] customizedRulePath,
            string[] includeRuleNames,
            string[] excludeRuleNames,
            string[] severity,
            bool includeDefaultRules = false,
            bool suppressedOnly = false,
            string profile = null)
        {
            if (outputWriter == null)
            {
                throw new ArgumentNullException("outputWriter");
            }
#if !PSV3
            this.moduleHandler = null;
#endif

            this.outputWriter = outputWriter;

#region Verifies rule extensions

            List<string> paths = this.GetValidCustomRulePaths(customizedRulePath, path);

            #endregion

#if CORECLR
            // For Full CLR logger is loaded via Composition
            // But for Core CLR we need to load it explicitly
            this.Loggers = GetInterfaceImplementationsFromAssembly<ILogger>();
#endif
            #region Initializes Rules

            var includeRuleList = new List<string>();
            var excludeRuleList = new List<string>();
            var severityList = new List<string>();

            if (profile != null)
            {
                ParseProfileString(profile, path, outputWriter, severityList, includeRuleList, excludeRuleList);
            }

            if (includeRuleNames != null)
            {
                foreach (string includeRuleName in includeRuleNames.Where(rule => !includeRuleList.Contains(rule, StringComparer.OrdinalIgnoreCase)))
                {
                    includeRuleList.Add(includeRuleName);
                }
            }

            if (excludeRuleNames != null)
            {
                foreach (string excludeRuleName in excludeRuleNames.Where(rule => !excludeRuleList.Contains(rule, StringComparer.OrdinalIgnoreCase)))
                {
                    excludeRuleList.Add(excludeRuleName);
                }
            }

            if (severity != null)
            {
                foreach (string sev in severity.Where(s => !severityList.Contains(s, StringComparer.OrdinalIgnoreCase)))
                {
                    severityList.Add(sev);
                }
            }

            this.suppressedOnly = suppressedOnly;
            this.includeRegexList = new List<Regex>();
            this.excludeRegexList = new List<Regex>();

            if (this.severity == null)
            {
                this.severity = severityList.Count == 0 ? null : severityList.ToArray();
            }
            else
            {
                this.severity = this.severity.Union(severityList).ToArray();
            }

            if (this.includeRule == null)
            {
                this.includeRule = includeRuleList.Count == 0 ? null : includeRuleList.ToArray();
            }
            else
            {
                this.includeRule = this.includeRule.Union(includeRuleList).ToArray();
            }

            if (this.excludeRule == null)
            {
                this.excludeRule = excludeRuleList.Count == 0 ? null : excludeRuleList.ToArray();
            }
            else
            {
                this.excludeRule = this.excludeRule.Union(excludeRuleList).ToArray();
            }

            //Check wild card input for the Include/ExcludeRules and create regex match patterns
            if (this.includeRule != null)
            {
                foreach (string rule in includeRule)
                {
                    Regex includeRegex = new Regex(String.Format("^{0}$", Regex.Escape(rule).Replace(@"\*", ".*")), RegexOptions.IgnoreCase);
                    this.includeRegexList.Add(includeRegex);
                }
            }

            if (this.excludeRule != null)
            {
                foreach (string rule in excludeRule)
                {
                    Regex excludeRegex = new Regex(String.Format("^{0}$", Regex.Escape(rule).Replace(@"\*", ".*")), RegexOptions.IgnoreCase);
                    this.excludeRegexList.Add(excludeRegex);
                }
            }

            try
            {
                this.LoadRules(this.validationResults, invokeCommand, includeDefaultRules);
                this.ConfigureScriptRules();
            }
            catch (Exception ex)
            {
                this.outputWriter.ThrowTerminatingError(
                    new ErrorRecord(
                        ex,
                        ex.HResult.ToString("X", CultureInfo.CurrentCulture),
                        ErrorCategory.NotSpecified, this));
            }

#endregion

#region Verify rules

            // Safely get one non-duplicated list of rules
            IEnumerable<IRule> rules =
                Enumerable.Union<IRule>(
                    Enumerable.Union<IRule>(
                        this.ScriptRules ?? Enumerable.Empty<IRule>(),
                        this.TokenRules ?? Enumerable.Empty<IRule>()),
                    this.ExternalRules ?? Enumerable.Empty<IExternalRule>());

            // Ensure that rules were actually loaded
            if (rules == null || rules.Any() == false)
            {
                this.outputWriter.ThrowTerminatingError(
                    new ErrorRecord(
                        new Exception(),
                        string.Format(
                            CultureInfo.CurrentCulture,
                            Strings.RulesNotFound),
                        ErrorCategory.ResourceExists,
                        this));
            }

#endregion
        }

        private List<string> GetValidCustomRulePaths(string[] customizedRulePath, PathIntrinsics path)
        {
            List<string> paths = new List<string>();

            if (customizedRulePath != null)
            {
                paths.AddRange(
                    customizedRulePath.ToList());
            }

            if (paths.Count > 0)
            {
                this.validationResults = this.CheckRuleExtension(paths.ToArray(), path);
                foreach (string extension in this.validationResults["InvalidPaths"])
                {
                    this.outputWriter.WriteWarning(string.Format(CultureInfo.CurrentCulture, Strings.MissingRuleExtension, extension));
                }
            }
            else
            {
                this.validationResults = new Dictionary<string, List<string>>();
                this.validationResults.Add("InvalidPaths", new List<string>());
                this.validationResults.Add("ValidModPaths", new List<string>());
                this.validationResults.Add("ValidDllPaths", new List<string>());
            }

            return paths;
        }


        private IEnumerable<T> GetInterfaceImplementationsFromAssembly<T>() where T : class
        {
            string dirName = Path.GetDirectoryName(typeof(ScriptAnalyzer).GetTypeInfo().Assembly.Location);
            var dllPaths = Directory.EnumerateFiles(dirName, "*.dll", SearchOption.TopDirectoryOnly);
            var objects = new List<T>();
            foreach (var dllPath in dllPaths)
            {
                outputWriter.WriteVerbose(string.Format("Found Assembly: {0}", dllPath));
                var objectsFromOneFile = GetInterfaceImplementationsFromAssembly<T>(dllPath);
                objects.AddRange(objectsFromOneFile);
            }
            return objects;
        }

        private IEnumerable<T> GetInterfaceImplementationsFromAssembly<T>(string ruleDllPath) where T : class
        {
            var fileName = Path.GetFileNameWithoutExtension(ruleDllPath);
            var assemblyName = new AssemblyName(fileName);
            outputWriter.WriteVerbose(string.Format("Loading Assembly:{0}", assemblyName.FullName));

            var dll = Assembly.Load(assemblyName);
            var rules = new List<T>();
            if (dll == null)
            {
                outputWriter.WriteVerbose(string.Format("Cannot load {0}", ruleDllPath));
                return rules;
            }
            foreach (var type in dll.ExportedTypes)
            {
                var typeInfo = type.GetTypeInfo();
                if (!typeInfo.IsInterface
                    && !typeInfo.IsAbstract
                    && typeInfo.ImplementedInterfaces.Contains(typeof(T)))
                {
                    outputWriter.WriteVerbose(
                        string.Format(
                            "Creating Instance of {0}", type.Name));

                    var ruleObj = Activator.CreateInstance(type);
                    T rule = ruleObj as T;
                    if (rule == null)
                    {
                        outputWriter.WriteVerbose(
                            string.Format(
                                "Cannot cast instance of type {0} to {1}", type.Name, typeof(T).GetTypeInfo().Name));
                        continue;
                    }
                    rules.Add(rule);
                }
            }
            return rules;
        }

        private void LoadRules(Dictionary<string, List<string>> result, CommandInvocationIntrinsics invokeCommand, bool loadBuiltInRules)
        {
            List<string> paths = new List<string>();

            // Clear external rules for each invoke.
            this.ScriptRules = null;
            this.TokenRules = null;
            this.ExternalRules = null;

#if CORECLR
            this.ScriptRules = GetInterfaceImplementationsFromAssembly<IScriptRule>();
            this.TokenRules = GetInterfaceImplementationsFromAssembly<ITokenRule>();
            this.DSCResourceRules = GetInterfaceImplementationsFromAssembly<IDSCResourceRule>();
#else
            // An aggregate catalog that combines multiple catalogs.
            using (AggregateCatalog catalog = new AggregateCatalog())
            {
                // Adds all the parts found in the same directory.
                string dirName = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
                catalog.Catalogs.Add(
                    new SafeDirectoryCatalog(
                        dirName,
                        this.outputWriter));

                // Adds user specified directory
                paths = result.ContainsKey("ValidDllPaths") ? result["ValidDllPaths"] : result["ValidPaths"];
                foreach (string path in paths)
                {
                    if (String.Equals(Path.GetExtension(path), ".dll", StringComparison.OrdinalIgnoreCase))
                    {
                        catalog.Catalogs.Add(new AssemblyCatalog(path));
                    }
                    else
                    {
                        catalog.Catalogs.Add(
                            new SafeDirectoryCatalog(
                                path,
                                this.outputWriter));
                    }
                }

                // Creates the CompositionContainer with the parts in the catalog.
                container = new CompositionContainer(catalog);

                // Fills the imports of this object.
                try
                {
                    container.ComposeParts(this);
                }
                catch (CompositionException compositionException)
                {
                    this.outputWriter.WriteWarning(compositionException.ToString());
                }
            }
#endif // CORECLR
            if (!loadBuiltInRules)
            {
                this.ScriptRules = null;
            }

            // Gets external rules.
            if (result.ContainsKey("ValidModPaths") && result["ValidModPaths"].Count > 0)
            {
                ExternalRules = GetExternalRule(result["ValidModPaths"].ToArray());
            }
        }

        // Configure rules derived from ConfigurableScriptRule class
        private void ConfigureScriptRules()
        {
            if (ScriptRules == null)
            {
                return;
            }

            foreach (var scriptRule in ScriptRules)
            {
                var configurableScriptRule = scriptRule as ConfigurableRule;
                if (configurableScriptRule == null)
                {
                    continue;
                }

                var paramValueMap = Helper.Instance.GetRuleArguments(scriptRule.GetName());
                if (paramValueMap == null)
                {