set-content and get-content's -encoding parameter doesn't tab complete to all options

Steps to reproduce

I think this inhibits discovery.

set-psreadlineoption -editmode emacs
'hi there' | set-content file -encoding #press tab

# for example this works for ebcdic (or ibm037):
'hi there' | set-content file -encoding ebcdic-cp-us

Expected behavior

# many encodings, more than listed by [System.Text.Encoding]::GetEncodings()

Actual behavior

ascii             bigendianutf32    unicode           utf8              utf8NoBOM
bigendianunicode  oem               utf7              utf8BOM           utf32

Environment data

Name                           Value
----                           -----
PSVersion                      7.1.1
PSEdition                      Core
GitCommitId                    7.1.1
OS                             Microsoft Windows 10.0.19042
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

[jszabo98]

A bit of a sidenote, but the displaynames of the encodings in the docs are completely different. Over 30 kinds of ebcdic! https://docs.microsoft.com/en-us/dotnet/api/system.text.encoding?view=net-5.0#list-of-encodings

<div>Encoding Class (System.Text)</div><div>Represents a character encoding. </div>

[jszabo98]

I don’t think this is too horrible if tab shows all options at once. Plus there’s the benefit of knowing this improvement actually exists. It’s like pressing tab after get-childitem in a folder with at least 100 files. It can be limited by typing the first few characters. It will ask first if you want to display all possibilities. (based on https://adamtheautomator.com/powershell-tab-completion/)

function Do-Thing {
    [CmdletBinding()]
    param(
        [Parameter()]
        [string]$Name
    )
    $Name
}

$scriptBlock = { [System.Text.Encoding]::GetEncodings().name }

Register-ArgumentCompleter -CommandName Do-Thing -ParameterName Name -ScriptBlock $scriptBlock


do-thing -name #tab

Display all 138 possibilities? (y or n) _

# 87x35

IBM037                   IBM01146                 x-cp20001                iso-8859-1
IBM437                   IBM01147                 x-Chinese-Eten           iso-8859-2
IBM500                   IBM01148                 x-cp20003                iso-8859-3
ASMO-708                 IBM01149                 x-cp20004                iso-8859-4
DOS-720                  utf-16                   x-cp20005                iso-8859-5
ibm737                   utf-16BE                 x-IA5                    iso-8859-6
ibm775                   windows-1250             x-IA5-German             iso-8859-7
ibm850                   windows-1251             x-IA5-Swedish            iso-8859-8
ibm852                   Windows-1252             x-IA5-Norwegian          iso-8859-9
IBM855                   windows-1253             us-ascii                 iso-8859-13
ibm857                   windows-1254             x-cp20261                iso-8859-15
IBM00858                 windows-1255             x-cp20269                x-Europa
IBM860                   windows-1256             IBM273                   iso-8859-8-i
ibm861                   windows-1257             IBM277                   iso-2022-jp
DOS-862                  windows-1258             IBM278                   csISO2022JP
IBM863                   Johab                    IBM280                   iso-2022-kr
IBM864                   macintosh                IBM284                   x-cp50227
IBM865                   x-mac-japanese           IBM285                   EUC-CN
cp866                    x-mac-chinesetrad        IBM290                   euc-kr
ibm869                   x-mac-korean             IBM297                   hz-gb-2312
IBM870                   x-mac-arabic             IBM420                   GB18030
windows-874              x-mac-hebrew             IBM423                   x-iscii-de
cp875                    x-mac-greek              IBM424                   x-iscii-be
shift_jis                x-mac-cyrillic           x-EBCDIC-KoreanExtended  x-iscii-ta
gb2312                   x-mac-chinesesimp        IBM-Thai                 x-iscii-te
ks_c_5601-1987           x-mac-romanian           koi8-r                   x-iscii-as
big5                     x-mac-ukrainian          IBM871                   x-iscii-or
IBM1026                  x-mac-thai               IBM880                   x-iscii-ka
IBM01047                 x-mac-ce                 IBM905                   x-iscii-ma
IBM01140                 x-mac-icelandic          IBM00924                 x-iscii-gu
IBM01141                 x-mac-turkish            EUC-JP                   x-iscii-pa
IBM01142                 x-mac-croatian           x-cp20936                utf-7
IBM01143                 utf-32                   x-cp20949                utf-8
IBM01144                 utf-32BE                 cp1025
IBM01145                 x-Chinese-CNS            koi8-u

<div> Adam the Automator</div><div>Dynamic Tab Completion with PowerShell ArgumentCompleters</div><div>Learn how to build some handy PowerShell tab-completion parameters that automatically update built by ArgumentCompleters.</div>