moby: ANSI Code Page in Hyper-V Windows containers should not be 65001

Description When running a Windows container with Hyper-V isolation, the system ANSI Code Page (ACP) is set to 65001, which corresponds to the UTF-8 code page, rather than to an “ordinary” code page.

For Windows Desktop, this is a Beta feature called “Beta: Use Unicode UTF-8 for worldwide language support”:

As this causes incompatibilities with software that doesn’t support UTF-8, it should not be enabled in containers by default.

• Most notoriously, this happens with SQL Server: https://github.com/microsoft/mssql-docker/issues/466#issuecomment-506079975
• But it also affects other software: https://social.msdn.microsoft.com/Forums/en-US/0c4a2452-efd5-4e39-bd58-9748201e1670/codepages-in-servercorenanoserver?forum=windowscontainers
• Another example: https://github.com/conda/conda/issues/8088

Repro steps without SQL Server:

1. Execute docker run -it --rm --isolation=hyperv mcr.microsoft.com/windows/servercore:1903 powershell
2. Inside the PowerShell, run this:

$Signature = "[DllImport(`"kernel32.dll`")] public static extern int GetACP();";$acpGetter = Add-Type -MemberDefinition $Signature -Name "Acp" -Namespace Win32Functions -PassThru; $acpGetter::GetACP()

1. Observe the results

Describe the results you received:

• With process isolation: 1252 (an “ordinary” code page)
• With Hyper-V isolation: 65001 (the UTF-8 code page)

Describe the results you expected: The selected code page shouldn’t be determined by a beta feature that’s not enabled on the host, regardless of the isolation mode. So it should either

• be the same as on the host OS (in my case, 1252),
• be hardcoded to something more friendly to non-UTF-8 applications,
• or be configurable at container start.

Output of docker version:

Client: Docker Engine - Community
 Version:           19.03.5
 API version:       1.40
 Go version:        go1.12.12
 Git commit:        633a0ea
 Built:             Wed Nov 13 07:22:37 2019
 OS/Arch:           windows/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          19.03.5
  API version:      1.40 (minimum version 1.24)
  Go version:       go1.12.12
  Git commit:       633a0ea
  Built:            Wed Nov 13 07:36:50 2019
  OS/Arch:          windows/amd64
  Experimental:     false

Output of docker info:

Client:
 Debug Mode: false

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 7
 Server Version: 19.03.5
 Storage Driver: windowsfilter
  Windows:
 Logging Driver: json-file
 Plugins:
  Volume: local
  Network: ics internal l2bridge l2tunnel nat null overlay private transparent
  Log: awslogs etwlogs fluentd gcplogs gelf json-file local logentries splunk syslog
 Swarm: inactive
 Default Isolation: hyperv
 Kernel Version: 10.0 18362 (18362.1.amd64fre.19h1_release.190318-1202)
 Operating System: Windows 10 Pro Version 1903 (OS Build 18362.592)
 OSType: windows
 Architecture: x86_64
 CPUs: 12
 Total Memory: 31.85GiB
 Name: W1119
 ID: 6SEL:LRZQ:3NZL:TEA3:KE36:A6UU:Y4WU:EXDA:PRKO:QSZQ:QQA3:V4WU
 Docker Root Dir: D:\DockerData
 Debug Mode: true
  File Descriptors: -1
  Goroutines: 28
  System Time: 2020-02-17T15:21:58.5160558+01:00
  EventsListeners: 1
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false
 Product License: Community Engine