Windows cmd shell: if-then-else weirdness for block statements - windows

Question

Trying to setup a simple build script that will expand the path based on other environment variables. This little script works fine:
echo off
call c:\vstudio\vc\bin\vcvars32.bat
set _ISGIT=1
echo current path is %PATH%
if defined _ISGIT set PATH=c:\git\bin;%PATH%
But if I want to do execute multiple lines based on the existence of the _ISGIT variable, then I thought this would work
echo off
call c:\vstudio\vc\bin\vcvars32.bat
set _ISGIT=1
echo current path is %PATH%
if defined _ISGIT (
set PATH=c:\git\bin;%PATH%
set PATH=c:\foo;%PATH%
)
But that yields the following output:
D:\>test.cmd
D:\>echo off
current path is C:\vstudio\Common7\IDE\CommonExtensions\Microsoft\TestWindow;C:\Program Files (x86)\MSBuild\14.0\bin;C:\
vstudio\Common7\IDE\;C:\vstudio\VC\BIN;C:\vstudio\Common7\Tools;C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319;C:\vstudio
\VC\VCPackages;C:\Program Files (x86)\HTML Help Workshop;C:\vstudio\Team Tools\Performance Tools;C:\Program Files (x86)\
Windows Kits\10\bin\x86;C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6.1 Tools\;C:\ProgramData\Oracl
e\Java\javapath;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\U
sers\jselbie\.dnx\bin;C:\Program Files\Microsoft DNX\Dnvm\;C:\Program Files (x86)\Windows Kits\10\Windows Performance To
olkit\;C:\Program Files\Microsoft SQL Server\130\Tools\Binn\;C:\nodejs\;C:\Program Files (x86)\Skype\Phone\;C:\WINDOWS\s
ystem32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\Program Files (x86)\NVIDIA Co
rporation\PhysX\Common;C:\Users\jselbie\.dnx\bin;C:\Users\jselbie\AppData\Roaming\npm;%USERPROFILE%\AppData\Local\Micros
oft\WindowsApps;
MSBuild\14.0\bin was unexpected at this time.
The MSBuild\14.0\bin was unexpected is likely a side effect of the original path containing a directory with a space. The presence of a space in the expanded command with the () seems to throw the script off.
How do I workaround this without having to have independent if defined statements?

Answer 1

There are two things wrong. First, one of the directories in the path contains parentheses. Variable expansion is performed before parsing, so the closing parenthesis from PATH is taken as the closing parenthesis of the IF block. To fix this, you need to put your assignment in quotes: set "PATH=...".
Secondly, inside a block (denoted by parentheses) all environment variables in the whole block are first expanded at once. Then the block is parsed. This means the expanded path in the second line is the same as it is on the first line. It is not changed by the first line. To fix this, you should either change the path entirely in one line:
if defined _ISGIT (
set "PATH=c:\foo;c:\git\bin;%PATH%"
)
or use delayed expansion:
setlocal enabledelayedexpansion
if defined _ISGIT (
set "PATH=c:\git\bin;!PATH!"
set "PATH=c:\foo;!PATH!"
)
Delayed expansion works by expanding a variable at a later stage, i.e. after the variable has been assigned by the first line. It has to be enabled with the setlocal command before it can be used.

Answer 2

set "PATH=c:\git\bin;%PATH%"
set "PATH=c:\foo;%PATH%"
using the quotes makes cmd interpret the quoted-string as a single token, so it doesn't see the ) within the variable [ie path] which is closing the if defined ... (

Answer 3

A contribution to nearly exhaustive Klitos Kyriacou's answer.
There is an implicit endlocal command at the end of a batch
file.
Hence, your test.cmd should be as follows (read ENDLOCAL):
#echo off
call c:\vstudio\vc\bin\vcvars32.bat
set _ISGIT=1
echo current path is %PATH%
setlocal enabledelayedexpansion
if defined _ISGIT (
set "PATH=c:\git\bin;!PATH!"
set "PATH=c:\foo;!PATH!"
)
endlocal&(
set "PATH=%PATH%"
)
or as follows (read CALL, note doubled percent signs):
#echo off
call c:\vstudio\vc\bin\vcvars32.bat
set _ISGIT=1
echo current path is %PATH%
if defined _ISGIT (
call set "PATH=c:\git\bin;%%PATH%%"
call set "PATH=c:\foo;%%PATH%%"
)