Initial draft of encoding rfc

Author: JamesWTruher

1-Draft/DefaultFileEncoding.md

@@ -0,0 +1,91 @@
+---
+RFC: Default File Encoding
+Author: James Truher
+Status: Draft
+Area: FileSystem
+Comments Due: 4/16/2017
+---
+
+# Default file encoding which optionally includes Byte Order Mark (BOM) 
+
+Ensuring file creation is proper for the platform, including whether the BOM should be written.
+
+## Motivation
+
+Current PowerShell behavior is that a BOM is created by default when a file is created for those encodings where the BOM is needed.
+This is a problem for Linux systems where the default encoding is UTF8 but a BOM is not written when a file is created.
+Creating files on Linux with a BOM makes it difficult to interact with the native tools, as the following example illustrates.
+
+```PowerShell
+PS> "ĝoo" > file.txt
+PS> get-content file.txt
+ĝoo
+PS> exit
+james@jimtru-ops2:~$ cat file.txt
+▒▒oo
+
+```
+This is due to the BOM being written into the file:
+```powershell
+PS /home/james> format-hex file.txt
+
+           Path: /home/james/file.txt
+           00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
+00000000   FF FE 1D 01 6F 00 6F 00 0A 00                    .þ..o.o...
+```
+The native tools on Linux try to render the BOM as actual content, which harms the output.
+If the BOM could be written when the platform expects it, interaction with native tools will be less problematic.
+
+## Specification
+
+A new global variable `$PSDefaultFileEncoding` shall be available which allows the user to define the encoding for their system.
+The allowed values for this variable shall be defined by
+
+We should take this opportunity to rationalize our use of the `Encoding` parameter, and change the cmdlets which use Encoding as `string` or `System.Text.Encoding` type to use `Microsoft.PowerShell.Commands.FileSystemCmdletProviderEncoding`.
+The following cmdlets use various types for the parameter `Encoding`
+
+```PowerShell
+PS> Get-Command -type cmdlet | ?{$\_.parameters} |?{$\_.source -match "microsoft"}|ft name,{$\_.parameters['encoding'].ParameterType}
+
+Name             $_.parameters['encoding'].ParameterType
+----             ---------------------------------------
+Add-Content      Microsoft.PowerShell.Commands.FileSystemCmdletProviderEncoding
+Export-Clixml    System.String
+Export-Csv       System.String
+Export-PSSession System.String
+Get-Content      Microsoft.PowerShell.Commands.FileSystemCmdletProviderEncoding
+Import-Csv       System.String
+Out-File         System.String
+Select-String    System.String
+Send-MailMessage System.Text.Encoding
+Set-Content      Microsoft.PowerShell.Commands.FileSystemCmdletProviderEncoding
+``` 
+
+`Microsoft.PowerShell.Commands.FileSystemCmdletProviderEncoding` shall be extended to include:
+
+* UTF8NoBOM
+
+which result in the membernames of this enum being:
+* Ascii
+* BigEndianUnicode
+* BigEndianUTF32
+* Byte
+* Default
+* Oem
+* String
+* Unicode
+* Unknown
+* UTF32
+* UTF7
+* UTF8
+* UTF8NoBOM
+
+The default on Windows systems shall remain unchanged, non-Windows platforms shall be defaulted to `UTF8NoBOM` via the `$PSDefaultFileEncoding` variable.
+If the `$PSDefaultFileEncoding` is not set, `UTF8NoBOM` shall be the default for non-Windows systems, and the current behavior () on Windows.
+
+### Examples
+
+### Commentary
+
+UTF8NoBOM is, of course, not an encoding but neither are a number of the other values for `FileSystemCmdletProviderEncoding`. 
+However, it _is_ descriptive of what we are doing.