Steps to reproduce

# make directories contains east asian fullwidth characters.
# in this example, I use Japanese.
mkdir .\Test
cd .\Test
mkdir Hello
mkdir HelloWorld
mkdir Helloワールド
mkdir ハロー
mkdir ハローワールド

# invoke Get-ChildItem (output table format by default)
Get-ChildItem

Expected behavior

Table layout is not broken.

e.g. on Windows PowerShell 5.1

Actual behavior

Table layout has been broken.

In this case, the last column(Name) is broken.
But the column other than the last column will also be broken.

Environment data

> $PSVersionTable
Name                           Value
----                           -----
PSVersion                      6.0.1
PSEdition                      Core
GitCommitId                    v6.0.1
OS                             Microsoft Windows 10.0.16299
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

This problem occurs on all platforms.

Cause

The root cause is ConsoleControl.LengthInBufferCells() method returns invalid value when str parameter contains east asian fullwidth characters.

When TableWriter creates table row line, ConsoleControl.LengthInBufferCells() method is called to get row character width.

ConsoleControl.LengthInBufferCells() method is expected to return a value according to the width of the character.
Generally, east asian fullwidth characters(e.g. Japanese) are expected to return 2 or more per a character, but current version of ConsoleControl.LengthInBufferCells() simply returns character length.

// length expected 6(3 fullwidth characters), but actual returns 3.
ConsoleControl.LengthInBufferCells("ハロー", 0, false); 

So, the padding in the last column(Name) has be greater than expected and then Table layout has been broken.

# expected 120 characters width
"d-----       2018/03/02     15:52                Hello                                                                 "
# actual 123 characters width
"d-----       2018/03/02     15:52                ハロー                                                                   "            

Reference 1

The past version of ConsoleControl.LengthInBufferCells() method calls LengthInBufferCellsFE() method internally. (FE means Far East?)

This LengthInBufferCellsFE() method handles the length of east asian fullwidth characters correctly, but it was removed at f604b0e .

Reference 2

Technical report about East Asian Width.

• East Asian Width