PR Summary

Improve processing of the powershell built-in type data from types.ps1xml, typesV3.ps1xml and GetEvent.types.ps1xml.

A few changes to speed up the processing of the built-in PowerShell type data.

1. Refactor TypeTable.cs a little to make it more efficiently at collection allocations.
   • Remove a few internal methods that are not used anywhere.
   • Update some code that does collection allocations to use a specific capacity, so as to avoid resizing or wasted allocations.
   • Add an new overload to ProcessStandardMembers, which takes an instance of PSMemberInfoInternalCollection<PSMemberInfo> directly that contains the standard members.
   • Separate out ProcessTypeConverter and ProcessTypeAdapter from ProcessTypeDataToAdd.
2. Add two overloads constructors to PSMemberSet and PSPropertySet that are used from TypeTable, which skip argument checks and reuse the passed in collection argument.
3. Generate code to register the built-in type information directly to the TypeTable without going through the TypeData representation as the intermediate step.
   • Currently the type information is represented by TypeData objects constructed in Types_Ps1Xml, TypesV3_Ps1Xml and GetEvent_Types_Ps1Xml. Then the TypeData objects are processed by TypeTable.ProcessTypeDataToAdd one by one.
   • I wrote a tool to go through the TypeData objects from Types_Ps1Xml.Get(), TypesV3_Ps1Xml.Get() and GetEvent_Types_Ps1Xml.Get() and generate the code that directly register the type information into TypeTable, so we can get rid of the intermediate step.
   • The tool can be found here. It's in one of the commits here, but was removed in a later commit as part of the cleanup work.
   • The new code are in TypeTable_Types_Ps1Xml.cs, TypeTable_Types_TypesV3_Ps1Xml.cs and TypeTable_GetEvent_Types_Ps1Xml. TypeTable is now declared as partial class, and spread in TypeTable.cs and the aforementioned 3 files.
4. Some more minor optimizations to the generated code, for example, use the cached ValueFactory delegate instance instead of create a new one for every duplicate one.

After this change, creating a default TypeTable instance those 3 built-in PowerShell type files takes about 47% less time at a stable state.

### 7.0.0-preview.5
PS> [string[]] $file = @("$PSHOME\types.ps1xml", "$PSHOME\typesv3.ps1xml", "$PSHOME\GetEvent.types.ps1xml")
>> Measure-Command { foreach($i in 1..100) { [System.Management.Automation.Runspaces.TypeTable]::new($file) } }

Days              : 0
Hours             : 0
Minutes           : 0
Seconds           : 0
Milliseconds      : 150
Ticks             : 1501009
TotalDays         : 1.73727893518519E-06
TotalHours        : 4.16946944444444E-05
TotalMinutes      : 0.00250168166666667
TotalSeconds      : 0.1501009
TotalMilliseconds : 150.1009

### After Change
PS> [string[]] $file = @("$PSHOME\types.ps1xml", "$PSHOME\typesv3.ps1xml", "$PSHOME\GetEvent.types.ps1xml")
>> Measure-Command { foreach($i in 1..100) { [System.Management.Automation.Runspaces.TypeTable]::new($file) } }

Days              : 0
Hours             : 0
Minutes           : 0
Seconds           : 0
Milliseconds      : 82
Ticks             : 827806
TotalDays         : 9.58108796296296E-07
TotalHours        : 2.29946111111111E-05
TotalMinutes      : 0.00137967666666667
TotalSeconds      : 0.0827806
TotalMilliseconds : 82.7806

Runspace.Open() is about 10% faster with the change at a stable state:

### 7.0.0-preview.5
PS> $iss = [initialsessionstate]::CreateDefault()
>> Measure-Command { foreach($i in 1..100) { $rs = [runspacefactory]::CreateRunspace($iss); $rs.Open(); $rs.Dispose() } }

Days              : 0
Hours             : 0
Minutes           : 0
Seconds           : 0
Milliseconds      : 495
Ticks             : 4954424
TotalDays         : 5.73428703703704E-06
TotalHours        : 0.000137622888888889
TotalMinutes      : 0.00825737333333333
TotalSeconds      : 0.4954424
TotalMilliseconds : 495.4424

### After Change
PS> $iss = [initialsessionstate]::CreateDefault()
>> Measure-Command { foreach($i in 1..100) { $rs = [runspacefactory]::CreateRunspace($iss); $rs.Open(); $rs.Dispose() } }

Days              : 0
Hours             : 0
Minutes           : 0
Seconds           : 0
Milliseconds      : 442
Ticks             : 4428146
TotalDays         : 5.12516898148148E-06
TotalHours        : 0.000123004055555556
TotalMinutes      : 0.00738024333333333
TotalSeconds      : 0.4428146
TotalMilliseconds : 442.8146

Memory allocation comparison
The profiling was taken using pwsh.exe -noprofile -c exit. The left side was built from master branch before this PR. The right side was built with the changes in this PR.

As the image below shows, the right side has less memory allocations in general.

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
• This PR is ready to merge and is not Work in Progress.
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• Breaking changes
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• User-facing changes
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• Testing - New and feature
  • N/A or can only be tested interactively
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  • Make sure you've added a new test if existing tests do not effectively test the code changed
• Tooling
  • I have considered the user experience from a tooling perspective and don't believe tooling will be impacted.
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    • Impact on PowerShell Editor Services which is used in the PowerShell extension for VSCode (which runs in a different PS Host).
    • Impact on Completions (both in the console and in editors) - one of PowerShell's most powerful features.
    • Impact on PSScriptAnalyzer (which provides linting & formatting in the editor extensions).
    • Impact on EditorSyntax (which provides syntax highlighting with in VSCode, GitHub, and many other editors).