GetCommandCommand.cs

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

using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Management.Automation;
using System.Management.Automation.Internal;
using System.Management.Automation.Language;
using System.Reflection;

using Dbg = System.Management.Automation.Diagnostics;

namespace Microsoft.PowerShell.Commands
{
    /// <summary>
    /// The get-command cmdlet.  It uses the command discovery APIs to find one or more
    /// commands of the given name.  It returns an instance of CommandInfo for each
    /// command that is found.
    /// </summary>
    [Cmdlet(VerbsCommon.Get, "Command", DefaultParameterSetName = "CmdletSet", HelpUri = "https://go.microsoft.com/fwlink/?LinkID=113309")]
    [OutputType(typeof(AliasInfo), typeof(ApplicationInfo), typeof(FunctionInfo),
                typeof(CmdletInfo), typeof(ExternalScriptInfo), typeof(FilterInfo),
                typeof(string), typeof(PSObject))]
    public sealed class GetCommandCommand : PSCmdlet
    {
        #region Definitions of cmdlet parameters

        /// <summary>
        /// Gets or sets the path(s) or name(s) of the commands to retrieve.
        /// </summary>
        [Parameter(
            Position = 0,
            ValueFromPipeline = true,
            ValueFromPipelineByPropertyName = true,
            ParameterSetName = "AllCommandSet")]
        [ValidateNotNullOrEmpty]
        public string[] Name
        {
            get
            {
                return _names;
            }

            set
            {
                _nameContainsWildcard = false;
                _names = value;

                if (value != null)
                {
                    foreach (string commandName in value)
                    {
                        if (WildcardPattern.ContainsWildcardCharacters(commandName))
                        {
                            _nameContainsWildcard = true;
                            break;
                        }
                    }
                }
            }
        }

        private string[] _names;
        private bool _nameContainsWildcard;

        /// <summary>
        /// Gets or sets the verb parameter to the cmdlet.
        /// </summary>
        [Parameter(ValueFromPipelineByPropertyName = true, ParameterSetName = "CmdletSet")]
        public string[] Verb
        {
            get
            {
                return _verbs;
            }

            set
            {
                if (value == null)
                {
                    value = Array.Empty<string>();
                }

                _verbs = value;
                _verbPatterns = null;
            }
        }

        private string[] _verbs = Array.Empty<string>();

        /// <summary>
        /// Gets or sets the noun parameter to the cmdlet.
        /// </summary>
        [Parameter(ValueFromPipelineByPropertyName = true, ParameterSetName = "CmdletSet")]
        [ArgumentCompleter(typeof(NounArgumentCompleter))]
        public string[] Noun
        {
            get
            {
                return _nouns;
            }

            set
            {
                if (value == null)
                {
                    value = Array.Empty<string>();
                }

                _nouns = value;
                _nounPatterns = null;
            }
        }

        private string[] _nouns = Array.Empty<string>();

        /// <summary>
        /// Gets or sets the PSSnapin/Module parameter to the cmdlet.
        /// </summary>
        [SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays", Justification = "Cmdlets use arrays for parameters.")]
        [Parameter(ValueFromPipelineByPropertyName = true)]
        [Alias("PSSnapin")]
        public string[] Module
        {
            get
            {
                return _modules;
            }

            set
            {
                if (value == null)
                {
                    value = Array.Empty<string>();
                }

                _modules = value;
                _modulePatterns = null;

                _isModuleSpecified = true;
            }
        }

        private string[] _modules = Array.Empty<string>();
        private bool _isModuleSpecified = false;

        /// <summary>
        /// Gets or sets the FullyQualifiedModule parameter to the cmdlet.
        /// </summary>
        [SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays", Justification = "Cmdlets use arrays for parameters.")]
        [Parameter(ValueFromPipelineByPropertyName = true)]
        public ModuleSpecification[] FullyQualifiedModule
        {
            get
            {
                return _moduleSpecifications;
            }

            set
            {
                if (value != null)
                {
                    _moduleSpecifications = value;
                }

                _isFullyQualifiedModuleSpecified = true;
            }
        }

        private ModuleSpecification[] _moduleSpecifications = Array.Empty<ModuleSpecification>();
        private bool _isFullyQualifiedModuleSpecified = false;

        /// <summary>
        /// Gets or sets the type of the command to get.
        /// </summary>
        [Parameter(ValueFromPipelineByPropertyName = true, ParameterSetName = "AllCommandSet")]
        [Alias("Type")]
        public CommandTypes CommandType
        {
            get
            {
                return _commandType;
            }

            set
            {
                _commandType = value;
                _isCommandTypeSpecified = true;
            }
        }

        private CommandTypes _commandType = CommandTypes.All;
        private bool _isCommandTypeSpecified = false;

        /// <summary>
        /// The parameter representing the total number of commands that will
        /// be returned. If negative, all matching commands that are found will
        /// be returned.
        /// </summary>
        [Parameter(ValueFromPipelineByPropertyName = true)]
        public int TotalCount { get; set; } = -1;

        /// <summary>
        /// The parameter that determines if the CommandInfo or the string
        /// definition of the command is output.
        /// </summary>
        [Parameter(ValueFromPipelineByPropertyName = true)]
        public SwitchParameter Syntax
        {
            get
            {
                return _usage;
            }

            set
            {
                _usage = value;
            }
        }

        private bool _usage;

        /// <summary>
        /// This parameter causes the output to be packaged into ShowCommandInfo PSObject types
        /// needed to display GUI command information.
        /// </summary>
        [Parameter()]
        public SwitchParameter ShowCommandInfo { get; set; }

        /// <summary>
        /// The parameter that all additional arguments get bound to. These arguments are used
        /// when retrieving dynamic parameters from cmdlets that support them.
        /// </summary>
        [Parameter(Position = 1, ValueFromRemainingArguments = true)]
        [AllowNull]
        [AllowEmptyCollection]
        [Alias("Args")]
        public object[] ArgumentList { get; set; }

        /// <summary>
        /// The parameter that determines if additional matching commands should be returned.
        /// (Additional matching functions and aliases are returned from module tables)
        /// </summary>
        [Parameter(ValueFromPipelineByPropertyName = true)]
        public SwitchParameter All
        {
            get { return _all; }

            set { _all = value; }
        }

        private bool _all;

        /// <summary>
        /// The parameter that determines if additional matching commands from available modules should be returned.
        /// If set to true, only those commands currently in the session are returned.
        /// </summary>
        [Parameter(ValueFromPipelineByPropertyName = true)]
        public SwitchParameter ListImported
        {
            get
            {
                return _listImported;
            }

            set
            {
                _listImported = value;
            }
        }

        private bool _listImported;

        /// <summary>
        /// The parameter that filters commands returned to only include commands that have a parameter with a name that matches one of the ParameterName's arguments.
        /// </summary>
        [Parameter]
        [ValidateNotNullOrEmpty]
        [SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays")]
        public string[] ParameterName
        {
            get { return _parameterNames; }

            set
            {
                if (value == null)
                {
                    throw new ArgumentNullException("value");
                }

                _parameterNames = value;
                _parameterNameWildcards = SessionStateUtilities.CreateWildcardsFromStrings(
                    _parameterNames,
                    WildcardOptions.CultureInvariant | WildcardOptions.IgnoreCase);
            }
        }

        private Collection<WildcardPattern> _parameterNameWildcards;
        private string[] _parameterNames;
        private HashSet<string> _matchedParameterNames;

        /// <summary>
        /// The parameter that filters commands returned to only include commands that have a parameter of a type that matches one of the ParameterType's arguments.
        /// </summary>
        [Parameter]
        [ValidateNotNullOrEmpty]
        [SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays")]
        public PSTypeName[] ParameterType
        {
            get
            {
                return _parameterTypes;
            }

            set
            {
                if (value == null)
                {
                    throw new ArgumentNullException("value");
                }

                // if '...CimInstance#Win32_Process' is specified, then exclude '...CimInstance'
                List<PSTypeName> filteredParameterTypes = new List<PSTypeName>(value.Length);
                for (int i = 0; i < value.Length; i++)
                {
                    PSTypeName ptn = value[i];

                    if (value.Any(otherPtn => otherPtn.Name.StartsWith(ptn.Name + "#", StringComparison.OrdinalIgnoreCase)))
                    {
                        continue;
                    }

                    if ((i != 0) && (ptn.Type != null) && (ptn.Type.Equals(typeof(object))))
                    {
                        continue;
                    }

                    filteredParameterTypes.Add(ptn);
                }

                _parameterTypes = filteredParameterTypes.ToArray();
            }
        }

        private PSTypeName[] _parameterTypes;

        /// <summary>
        /// Gets or sets the parameter that enables using fuzzy matching.
        /// </summary>
        [Parameter(ParameterSetName = "AllCommandSet")]
        public SwitchParameter UseFuzzyMatching { get; set; }

        private List<CommandScore> _commandScores = new List<CommandScore>();

        /// <summary>
        /// Gets or sets the parameter that determines if return cmdlets based on abbreviation expansion.
        /// This means it matches cmdlets where the uppercase characters for the noun match
        /// the given characters.  i.e., g-sgc would match Get-SomeGreatCmdlet.
        /// </summary>
        [Parameter(ValueFromPipelineByPropertyName = true, ParameterSetName = "AllCommandSet")]
        public SwitchParameter UseAbbreviationExpansion { get; set; }

        #endregion Definitions of cmdlet parameters

        #region Overrides

        /// <summary>
        /// Begin Processing.
        /// </summary>
        protected override void BeginProcessing()
        {
            _timer.Start();

            base.BeginProcessing();

            if (ShowCommandInfo.IsPresent && Syntax.IsPresent)
            {
                ThrowTerminatingError(
                    new ErrorRecord(
                        new PSArgumentException(DiscoveryExceptions.GetCommandShowCommandInfoParamError),
                        "GetCommandCannotSpecifySyntaxAndShowCommandInfoTogether",
                        ErrorCategory.InvalidArgument,
                        null));
            }
        }

        /// <summary>
        /// Method that implements get-command.
        /// </summary>
        protected override void ProcessRecord()
        {
            // Module and FullyQualifiedModule should not be specified at the same time.
            // Throw out terminating error if this is the case.
            if (_isModuleSpecified && _isFullyQualifiedModuleSpecified)
            {
                string errMsg = string.Format(CultureInfo.InvariantCulture, SessionStateStrings.GetContent_TailAndHeadCannotCoexist, "Module", "FullyQualifiedModule");
                ErrorRecord error = new ErrorRecord(new InvalidOperationException(errMsg), "ModuleAndFullyQualifiedModuleCannotBeSpecifiedTogether", ErrorCategory.InvalidOperation, null);
                ThrowTerminatingError(error);
            }

            // Initialize the module patterns
            if (_modulePatterns == null)
            {
                _modulePatterns = SessionStateUtilities.CreateWildcardsFromStrings(Module, WildcardOptions.IgnoreCase | WildcardOptions.CultureInvariant);
            }

            switch (ParameterSetName)
            {
                case "CmdletSet":
                    AccumulateMatchingCmdlets();
                    break;

                case "AllCommandSet":
                    AccumulateMatchingCommands();
                    break;

                default:
                    Dbg.Assert(
                        false,
                        "Only the valid parameter set names should be used");
                    break;
            }
        }

        /// <summary>
        /// Writes out the accumulated matching commands.
        /// </summary>
        protected override void EndProcessing()
        {
            // We do not show the pithy aliases (not of the format Verb-Noun) and applications by default.
            // We will show them only if the Name, All and totalCount are not specified.
            if ((this.Name == null) && (!_all) && TotalCount == -1 && !UseFuzzyMatching)
            {
                CommandTypes commandTypesToIgnore = 0;

                if (((this.CommandType & CommandTypes.Alias) != CommandTypes.Alias) || (!_isCommandTypeSpecified))
                {
                    commandTypesToIgnore |= CommandTypes.Alias;
                }

                if (((_commandType & CommandTypes.Application) != CommandTypes.Application) ||
                    (!_isCommandTypeSpecified))
                {
                    commandTypesToIgnore |= CommandTypes.Application;
                }

                _accumulatedResults =
                    _accumulatedResults.Where(
                        commandInfo =>
                        (((commandInfo.CommandType & commandTypesToIgnore) == 0) ||
                         (commandInfo.Name.IndexOf('-') > 0))).ToList();
            }

            // report not-found errors for ParameterName and ParameterType if needed
            if ((_matchedParameterNames != null) && (ParameterName != null))
            {
                foreach (string requestedParameterName in ParameterName)
                {
                    if (WildcardPattern.ContainsWildcardCharacters(requestedParameterName))
                    {
                        continue;
                    }

                    if (_matchedParameterNames.Contains(requestedParameterName))
                    {
                        continue;
                    }

                    string errorMessage = string.Format(
                        CultureInfo.InvariantCulture,
                        DiscoveryExceptions.CommandParameterNotFound,
                        requestedParameterName);
                    var exception = new ArgumentException(errorMessage, requestedParameterName);
                    var errorRecord = new ErrorRecord(exception, "CommandParameterNotFound",
                                                      ErrorCategory.ObjectNotFound, requestedParameterName);
                    WriteError(errorRecord);
                }
            }

            // Only sort if they didn't fully specify a name)
            if ((_names == null) || (_nameContainsWildcard))
            {
                // Use the stable sorting to sort the result list
                _accumulatedResults = _accumulatedResults.OrderBy(a => a, new CommandInfoComparer()).ToList();
            }

            OutputResultsHelper(_accumulatedResults);

            object pssenderInfo = Context.GetVariableValue(SpecialVariables.PSSenderInfoVarPath);
            if ((pssenderInfo != null) && (pssenderInfo is System.Management.Automation.Remoting.PSSenderInfo))
            {
                // Win8: 593295. Exchange has around 1000 cmdlets. During Import-PSSession,
                // Get-Command  | select-object ..,HelpURI,... is run. HelpURI is a script property
                // which in turn runs Get-Help. Get-Help loads the help content and caches it in the process.
                // This caching is using around 190 MB. During V3, we have implemented HelpURI attribute
                // and this should solve it. In V2, we dont have this attribute and hence 3rd parties
                // run into the same issue. The fix here is to reset help cache whenever get-command is run on
                // a remote endpoint. In the worst case, this will affect get-help to run a little longer
                // after get-command is run..but that should be OK because get-help is used mainly for
                // document reading purposes and not in production.
                Context.HelpSystem.ResetHelpProviders();
            }
        }

        #endregion

        #region Private Methods

        private void OutputResultsHelper(IEnumerable<CommandInfo> results)
        {
            CommandOrigin origin = this.MyInvocation.CommandOrigin;

            if (UseFuzzyMatching)
            {
                results = _commandScores.OrderBy(x => x.Score).Select(x => x.Command).ToList();
            }

            int count = 0;
            foreach (CommandInfo result in results)
            {
                count += 1;
                // Only write the command if it is visible to the requestor
                if (SessionState.IsVisible(origin, result))
                {
                    // If the -syntax flag was specified, write the definition as a string
                    // otherwise just return the object...
                    if (Syntax)
                    {
                        if (!string.IsNullOrEmpty(result.Syntax))
                        {
                            PSObject syntax = PSObject.AsPSObject(result.Syntax);

                            syntax.IsHelpObject = true;

                            WriteObject(syntax);
                        }
                    }
                    else
                    {
                        if (ShowCommandInfo.IsPresent)
                        {
                            // Write output as ShowCommandCommandInfo object.
                            WriteObject(
                                ConvertToShowCommandInfo(result));
                        }
                        else
                        {
                            // Write output as normal command info object.
                            WriteObject(result);
                        }
                    }
                }
            }

            _timer.Stop();

#if LEGACYTELEMETRY
            // We want telementry on commands people look for but don't exist - this should give us an idea
            // what sort of commands people expect but either don't exist, or maybe should be installed by default.
            // The StartsWith is to avoid logging telemetry when suggestion mode checks the
            // current directory for scripts/exes in the current directory and '.' is not in the path.
            if (count == 0 && Name != null && Name.Length > 0 && !Name[0].StartsWith(".\\", StringComparison.OrdinalIgnoreCase))
            {
                Telemetry.Internal.TelemetryAPI.ReportGetCommandFailed(Name, _timer.ElapsedMilliseconds);
            }
#endif
        }

        /// <summary>
        /// The comparer to sort CommandInfo objects in the result list.
        /// </summary>
        private class CommandInfoComparer : IComparer<CommandInfo>
        {
            /// <summary>
            /// Compare two CommandInfo objects first by their command types, and if they
            /// are with the same command type, then we compare their names.
            /// </summary>
            /// <param name="x"></param>
            /// <param name="y"></param>
            /// <returns></returns>
            public int Compare(CommandInfo x, CommandInfo y)
            {
                if ((int)x.CommandType < (int)y.CommandType)
                {
                    return -1;
                }
                else if ((int)x.CommandType > (int)y.CommandType)
                {
                    return 1;
                }
                else
                {
                    return string.Compare(x.Name, y.Name, StringComparison.OrdinalIgnoreCase);
                }
            }
        }

        private void AccumulateMatchingCmdlets()
        {
            _commandType = CommandTypes.Cmdlet | CommandTypes.Function | CommandTypes.Filter | CommandTypes.Alias | CommandTypes.Configuration;

            Collection<string> commandNames = new Collection<string>();
            commandNames.Add("*");
            AccumulateMatchingCommands(commandNames);
        }

        private bool IsNounVerbMatch(CommandInfo command)
        {
            bool result = false;

            do // false loop
            {
                if (_verbPatterns == null)
                {
                    _verbPatterns = SessionStateUtilities.CreateWildcardsFromStrings(Verb, WildcardOptions.IgnoreCase | WildcardOptions.CultureInvariant);
                }

                if (_nounPatterns == null)
                {
                    _nounPatterns = SessionStateUtilities.CreateWildcardsFromStrings(Noun, WildcardOptions.IgnoreCase | WildcardOptions.CultureInvariant);
                }

                if (!string.IsNullOrEmpty(command.ModuleName))
                {
                    if (_isFullyQualifiedModuleSpecified)
                    {
                        if (!_moduleSpecifications.Any(
                                moduleSpecification =>
                                ModuleIntrinsics.IsModuleMatchingModuleSpec(command.Module, moduleSpecification)))
                        {
                            break;
                        }
                    }
                    else if (!SessionStateUtilities.MatchesAnyWildcardPattern(command.ModuleName, _modulePatterns, true))
                    {
                        break;
                    }
                }
                else
                {
                    if (_modulePatterns.Count > 0 || _moduleSpecifications.Any())
                    {
                        // Its not a match if we are filtering on a PSSnapin/Module name but the cmdlet doesn't have one.
                        break;
                    }
                }

                // Get the noun and verb to check...
                string verb;
                string noun;
                CmdletInfo cmdlet = command as CmdletInfo;
                if (cmdlet != null)
                {
                    verb = cmdlet.Verb;
                    noun = cmdlet.Noun;
                }
                else
                {
                    if (!CmdletInfo.SplitCmdletName(command.Name, out verb, out noun))
                        break;
                }

                if (!SessionStateUtilities.MatchesAnyWildcardPattern(verb, _verbPatterns, true))
                {
                    break;
                }

                if (!SessionStateUtilities.MatchesAnyWildcardPattern(noun, _nounPatterns, true))
                {
                    break;
                }

                result = true;
            } while (false);

            return result;
        }

        /// <summary>
        /// Writes out the commands for the AllCommandSet using the specified CommandType.
        /// </summary>
        private void AccumulateMatchingCommands()
        {
            Collection<string> commandNames =
                SessionStateUtilities.ConvertArrayToCollection<string>(this.Name);

            if (commandNames.Count == 0)
            {
                commandNames.Add("*");
            }

            AccumulateMatchingCommands(commandNames);
        }

        private void AccumulateMatchingCommands(IEnumerable<string> commandNames)
        {
            // First set the search options

            SearchResolutionOptions options = SearchResolutionOptions.None;
            if (All)
            {
                options = SearchResolutionOptions.SearchAllScopes;
            }

            if (UseAbbreviationExpansion)
            {
                options |= SearchResolutionOptions.UseAbbreviationExpansion;
            }

            if (UseFuzzyMatching)
            {
                options |= SearchResolutionOptions.FuzzyMatch;
            }

            if ((this.CommandType & CommandTypes.Alias) != 0)
            {
                options |= SearchResolutionOptions.ResolveAliasPatterns;
            }

            if ((this.CommandType & (CommandTypes.Function | CommandTypes.Filter | CommandTypes.Configuration)) != 0)
            {
                options |= SearchResolutionOptions.ResolveFunctionPatterns;
            }

            foreach (string commandName in commandNames)
            {
                try
                {
                    // Determine if the command name is module-qualified, and search
                    // available modules for the command.
                    string moduleName;
                    string plainCommandName = Utils.ParseCommandName(commandName, out moduleName);
                    bool isModuleQualified = (moduleName != null);

                    // If they've specified a module name, we can do some smarter filtering.
                    // Otherwise, we have to filter everything.
                    if ((this.Module.Length == 1) && (!WildcardPattern.ContainsWildcardCharacters(this.Module[0])))
                    {
                        moduleName = this.Module[0];
                    }

                    bool isPattern = WildcardPattern.ContainsWildcardCharacters(plainCommandName) || UseAbbreviationExpansion || UseFuzzyMatching;
                    if (isPattern)
                    {
                        options |= SearchResolutionOptions.CommandNameIsPattern;
                    }

                    // Try to initially find the command in the available commands
                    int count = 0;
                    bool isDuplicate;
                    bool resultFound = FindCommandForName(options, commandName, isPattern, true, ref count, out isDuplicate);

                    // If we didn't find the command, or if it had a wildcard, also see if it
                    // is in an available module
                    if (!resultFound || isPattern)
                    {
                        // If the command name had no wildcards or was module-qualified,
                        // import the module so that we can return the fully structured data.
                        // This uses the same code path as module auto-loading.
                        if ((!isPattern) || (!string.IsNullOrEmpty(moduleName)))
                        {
                            string tempCommandName = commandName;
                            if ((!isModuleQualified) && (!string.IsNullOrEmpty(moduleName)))
                            {
                                tempCommandName = moduleName + "\\" + commandName;
                            }

                            try
                            {
                                CommandDiscovery.LookupCommandInfo(tempCommandName, this.MyInvocation.CommandOrigin, this.Context);
                            }
                            catch (CommandNotFoundException)
                            {
                                // Ignore, LookupCommandInfo doesn't handle wildcards.
                            }

                            resultFound = FindCommandForName(options, commandName, isPattern, false, ref count, out isDuplicate);
                        }
                        // Show additional commands from available modules only if ListImported is not specified
                        else if (!ListImported)
                        {
                            if (TotalCount < 0 || count < TotalCount)
                            {
                                IEnumerable<CommandInfo> commands;
                                if (UseFuzzyMatching)
                                {
                                    foreach (var commandScore in System.Management.Automation.Internal.ModuleUtils.GetFuzzyMatchingCommands(
                                        plainCommandName,
                                        this.Context,
                                        this.MyInvocation.CommandOrigin,
                                        rediscoverImportedModules: true,
                                        moduleVersionRequired: _isFullyQualifiedModuleSpecified))
                                    {
                                        _commandScores.Add(commandScore);
                                    }

                                    commands = _commandScores.Select(x => x.Command).ToList();
                                }
                                else
                                {
                                    commands = System.Management.Automation.Internal.ModuleUtils.GetMatchingCommands(
                                        plainCommandName,
                                        this.Context,
                                        this.MyInvocation.CommandOrigin,
                                        rediscoverImportedModules: true,
                                        moduleVersionRequired: _isFullyQualifiedModuleSpecified,
                                        useAbbreviationExpansion: UseAbbreviationExpansion);
                                }

                                foreach (CommandInfo command in commands)
                                {
                                    // Cannot pass in "command" by ref (foreach iteration variable)
                                    CommandInfo current = command;

                                    if (IsCommandMatch(ref current, out isDuplicate) && (!IsCommandInResult(current)) && IsParameterMatch(current))
                                    {
                                        _accumulatedResults.Add(current);

                                        // Make sure we don't exceed the TotalCount parameter
                                        ++count;

                                        if (TotalCount >= 0 && count >= TotalCount)
                                        {
                                            break;
                                        }
                                    }
                                }
                            }
                        }
                    }

                    // If we are trying to match a single specific command name (no glob characters)
                    // then we need to write an error if we didn't find it.
                    if (!isDuplicate)
                    {
                        if (!resultFound && !isPattern)
                        {
                            CommandNotFoundException e =
                                new CommandNotFoundException(
                                    commandName,
                                    null,
                                    "CommandNotFoundException",
                                    DiscoveryExceptions.CommandNotFoundException);

                            WriteError(
                                new ErrorRecord(
                                    e.ErrorRecord,
                                    e));
                            continue;
                        }
                    }
                }
                catch (CommandNotFoundException exception)
                {
                    WriteError(
                        new ErrorRecord(
                            exception.ErrorRecord,
                            exception));
                }
            }
        }

        private bool FindCommandForName(SearchResolutionOptions options, string commandName, bool isPattern, bool emitErrors, ref int currentCount, out bool isDuplicate)
        {
            CommandSearcher searcher =
                    new CommandSearcher(
                        commandName,
                        options,
                        this.CommandType,
                        this.Context);

            bool resultFound = false;
            isDuplicate = false;

            do
            {
                try
                {
                    if (!searcher.MoveNext())
                    {
                        break;
                    }
                }
                catch (ArgumentException argumentException)
                {
                    if (emitErrors)
                    {
                        WriteError(new ErrorRecord(argumentException, "GetCommandInvalidArgument", ErrorCategory.SyntaxError, null));
                    }

                    continue;
                }
                catch (PathTooLongException pathTooLong)
                {
                    if (emitErrors)
                    {
                        WriteError(new ErrorRecord(pathTooLong, "GetCommandInvalidArgument", ErrorCategory.SyntaxError, null));
                    }

                    continue;
                }
                catch (FileLoadException fileLoadException)
                {
                    if (emitErrors)
                    {
                        WriteError(new ErrorRecord(fileLoadException, "GetCommandFileLoadError", ErrorCategory.ReadError, null));
                    }

                    continue;
                }
                catch (MetadataException metadataException)
                {
                    if (emitErrors)
                    {
                        WriteError(new ErrorRecord(metadataException, "GetCommandMetadataError", ErrorCategory.MetadataError, null));
                    }

                    continue;
                }
                catch (FormatException formatException)
                {
                    if (emitErrors)
                    {
                        WriteError(new ErrorRecord(formatException, "GetCommandBadFileFormat", ErrorCategory.InvalidData, null));
                    }

                    continue;
                }

                CommandInfo current = ((IEnumerator<CommandInfo>)searcher).Current;

                // skip private commands as early as possible
                // (i.e. before setting "result found" flag and before trying to use ArgumentList parameter)
                // see bugs Windows 7: #520498 and #520470
                CommandOrigin origin = this.MyInvocation.CommandOrigin;
                if (!SessionState.IsVisible(origin, current))
                {
                    continue;
                }

                bool tempResultFound = IsCommandMatch(ref current, out isDuplicate);

                if (tempResultFound && (!IsCommandInResult(current)))
                {
                    resultFound = true;
                    if (IsParameterMatch(current))
                    {
                        // Make sure we don't exceed the TotalCount parameter
                        ++currentCount;

                        if (TotalCount >= 0 && currentCount > TotalCount)
                        {
                            break;
                        }

                        if (UseFuzzyMatching)
                        {
                            int score = FuzzyMatcher.GetDamerauLevenshteinDistance(current.Name, commandName);
                            _commandScores.Add(new CommandScore(current, score));
                        }

                        _accumulatedResults.Add(current);

                        if (ArgumentList != null)
                        {
                            // Don't iterate the enumerator any more. If -arguments was specified, then we stop at the first match
                            break;
                        }
                    }

                    // Only for this case, the loop should exit
                    // Get-Command Foo
                    if (isPattern || All || TotalCount != -1 || _isCommandTypeSpecified || _isModuleSpecified || _isFullyQualifiedModuleSpecified)
                    {
                        continue;
                    }
                    else
                    {
                        break;
                    }
                }
            } while (true);

            if (All)
            {
                // Get additional matching commands from module tables.
                foreach (CommandInfo command in GetMatchingCommandsFromModules(commandName))
                {
                    CommandInfo c = command;
                    bool tempResultFound = IsCommandMatch(ref c, out isDuplicate);
                    if (tempResultFound)
                    {
                        resultFound = true;