Fix formatting truncation to handle strings with VT sequences

[daxian-dbw]

PR Summary

Fix #16700

Fix formatting truncation to handle strings with VT sequences.
The main changes are in buffer cell length calculation, as well as adding VtSubstring implementations, which are used to get part of a string that may contain escape sequences.

With the changes in this PR, the formatting works fine with the demo scripts from #16700 (comment) and #16700 (comment):

function Get-DemoObjects {
    [PSCustomObject]@{PSTypeName = "User"; Name = "Bob Saggat"; Tenure = 2; Role = "Developer" }
    [PSCustomObject]@{PSTypeName = "User"; Name = "John Seymour"; Tenure = 6; Role = "Sw Engineer" }
    [PSCustomObject]@{PSTypeName = "User"; Name = "Billy Bob Thorton"; Tenure = 13; Role = "Senior DevOps Engineer" }
}

Get-DemoObjects |
    Format-Table @{Width = 10; Name = "Name"; E = { (@("`e[32m", "`e[34m", "`e[33m", "`e[31m", "`e[33m", "`e[34m", "`e[32m")[[array]::BinarySearch(@(3, 5, 8), $_.Tenure)]) + $_.Name + "`e[39m"}},
                 @{Width = 15; Name = "Role";  E = { $_.Role }}, 
                 @{Width = 3; Name = "YIR";  E = { $_.Tenure }}

Get-DemoObjects |
    Format-Table @{Width = 10; Name = "Name"; E = { (@("`e[32m", "`e[34m", "`e[33m", "`e[31m", "`e[33m", "`e[34m", "`e[32m")[[array]::BinarySearch(@(3, 5, 8), $_.Tenure)]) + $_.Name + "`e[39m"}},
                 @{Width = 15; Name = "Role";  E = {
                                -join $(switch -regex ($_.Role){
                                        "Senior" { "`e[42m" }
                                        "Engineer" { "`e[1;33m" }
                                    }) + $_.Role  + "`e[0m"}}, 
                 @{Width = 3; Name = "YIR";  E = { $_.Tenure }}

$PSStyle.OutputRendering = "Ansi"
(Get-DemoObjects) + (Get-DemoObjects) + 
(Get-DemoObjects) + (Get-DemoObjects) + 
(Get-DemoObjects) + (Get-DemoObjects) | 
    Format-Wide @{E = { (@("`e[32m", "`e[34m", "`e[33m", "`e[31m", "`e[33m", "`e[34m", "`e[32m")[[array]::BinarySearch(@(3, 5, 8), $_.Tenure)]) + $_.Name + "`e[39m"}} -co 2 | Out-String -Width 47

Get-DemoObjects | Format-Table @{Width = 10; Name = "Name"; E = { "`e[33m" + $_.Name } }, 
                               @{Width = 15; Name = "Role"; E = { $_.Role }},
                               @{Width = 3;  Name = "YIR";  E = { $_.Tenure }}

Get-DemoObjects | Format-Table @{Width = 10; Name = "Name"; E = { "`e[1;33m" + $_.Name } }, 
                               @{Width = 15; Name = "Role"; E = { $_.Role }},
                               @{Width = 3;  Name = "YIR";  E = { $_.Tenure }}

Using the repro provided in #16700 (comment), now the formatting truncation and alignment work as expected:

Out-String works as well:

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[daxian-dbw]

@SeeminglyScience Now that the default buffer cell calculation takes into account escape sequences and CJK characters, I think we can make ConsoleHost and VSCode host to use the default DisplayCells instead of calling into the host specific LengthInBufferCells method. Let me know if you have any concerns.

[SeeminglyScience]

@SeeminglyScience Now that the default buffer cell calculation takes into account escape sequences and CJK characters, I think we can make ConsoleHost and VSCode host to use the default DisplayCells instead of calling into the host specific LengthInBufferCells method. Let me know if you have any concerns.

I agree! VSCode just redirects to ConsoleHost*'s implementation so shouldn't need any changes there.

Also does this mean that piping to line output writers that aren't host aware should work now too? 😮 (e.g. Out-String and less.exe would calculate the wrong value width because they never call LengthInBufferCells)

[daxian-dbw]

Yes, Out-String works too. I will add a screenshot to the description about this.
[update] screenshot added. Also add it here:

[PaulHigin]

LGTM

[SeeminglyScience]

Very clever fix, well done! LGTM ❤️

[ghost]

🎉v7.3.0-preview.4 has been released which incorporates this pull request.:tada:

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