BATCH why does running this FOR loop inside an IF statement not work until I run it once outside of it [duplicate] - batch-file

Question

This question already has an answer here:
Variables are not behaving as expected
(1 answer)
Closed 24 days ago.
I've been racking my head over my script on why the section for finding out the directory size in bytes does not work but after a long time of debugging i've encountered the following scenario:
if I run the for loop inside an IF statement it doesn't work
if I run the for loop outside the IF statement it does work
if I run the for loop outside the IF statement and then run it inside afterwards, it does work
Is the for loop written incorrectly or am I misunderstanding or missing something?
The following does NOT work
#ECHO OFF
set "test=1"
if %test% GTR 0 (
echo Scenario A
pushd "%~dp0"
set dir="C:\temp"
for /f "tokens=3" %%i in ('robocopy /l /e /bytes %dir% %dir% ^| findstr Bytes') do set size=%%i
echo Size = %size%
pause
) else (
echo Scenario B
pause
)
But this DOES work for both runs
#ECHO OFF
set "test=1"
echo Method a
pushd "%~dp0"
set dir="C:\temp""
for /f "tokens=3" %%i in ('robocopy /l /e /bytes %dir% %dir% ^| findstr Bytes') do set size=%%i
echo Size = %size%
echo Now Method A in IF statement
if %test% GTR 0 (
echo Scenario A
pushd "%~dp0"
set dir="C:\temp"
for /f "tokens=3" %%i in ('robocopy /l /e /bytes %dir% %dir% ^| findstr Bytes') do set size=%%i
echo Size = %size%
pause
) else (
echo Scenario B
pause
)

Answer 1

The reason is that variables in if/else statement are expanded before executing it. You are setting dir variable inside it, but all %dir% occurrences are expanded at the same time, before running if/else.
Basically the following command is actually executed. As you can see all variables were expanded:
if 1 GTR 0 (
echo Scenario A
pushd "C:\Workdir\"
set dir="C:\temp"
for /f "tokens=3" %i in ('robocopy /l /e /bytes | findstr Bytes') do set size=%i
echo Size =
pause
) else (
echo Scenario B
pause
)
As an alternative you can use if/goto commands to organize the flow. In this case every command will be expanded individually. It will look like this:
if %test% NEQ 1 goto ScenarioB
rem Scenario A
goto Done
:ScenarioB
rem Scenario B
:Done
Also double quotes are not needed in set test=1.
To troubleshoot such issues you can turn echo on, then you will see the commands being executed.