Display changes of environment variables by vcvars64.bat

tasks.json

{
    // See https://go.microsoft.com/fwlink/?LinkId=733558
    // for the documentation about the tasks.json format
    "version": "2.0.0",
    "tasks": [
        {
            "label": "build",
            "type": "shell",
            "command": "meson build --backend vs",
            "options": {
                "env": {
                    "VSINSTALLDIR": "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\",
                    "PATH": "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\VC\\Tools\\MSVC\\14.24.28314\\bin\\HostX64\\x64;C:\\Program Files (x86)\\Windows Kits\\10\\bin\\10.0.18362.0\\x64;",
                    "INCLUDE": "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\VC\\Tools\\MSVC\\14.24.28314\\ATLMFC\\include;C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\VC\\Tools\\MSVC\\14.24.28314\\include;C:\\Program Files (x86)\\Windows Kits\\10\\include\\10.0.18362.0\\ucrt;C:\\Program Files (x86)\\Windows Kits\\10\\include\\10.0.18362.0\\shared;C:\\Program Files (x86)\\Windows Kits\\10\\include\\10.0.18362.0\\um;C:\\Program Files (x86)\\Windows Kits\\10\\include\\10.0.18362.0\\winrt;C:\\Program Files (x86)\\Windows Kits\\10\\include\\10.0.18362.0\\cppwinrt",
                    "LIB": "C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\Community\\VC\\Tools\\MSVC\\14.24.28314\\lib\\x64;C:\\Program Files (x86)\\Windows Kits\\10\\lib\\10.0.18362.0\\ucrt\\x64;C:\\Program Files (x86)\\Windows Kits\\10\\lib\\10.0.18362.0\\um\\x64;",
                }
            },
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "problemMatcher": []
        }
    ]
}

vcvars.ps1

$ErrorActionPreference = "Stop"

$path = Get-VSSetupInstance `
  | Select-VSSetupInstance -Require Microsoft.VisualStudio.Workload.NativeDesktop -Latest `
  | Select-Object -ExpandProperty InstallationPath;
# echo $path
$bat = "$path\VC\Auxiliary\Build\vcvars64.bat"

$before = cmd /c "set"
$after = cmd /c "`"$bat`" > NUL & set"

function ToMap($src)
{
    $map = @{}
    foreach($l in $src)
    {
        $k, $v = $l.split('=')
        $map.Add($k, $v)
    }
    return $map
}

$before = ToMap($before)
$beforePath = $before["PATH"].split(';')
$before.remove("PATH")

$after = ToMap($after)
$afterPath = $after["PATH"].split(';')
$after.remove("PATH")

$ignore = @("__VSCMD_PREINIT_PATH")
foreach($k in $after.Keys)
{
    if($ignore -Contains $k)
    {
        continue
    }
    
    if($before[$k])
    {
        if($before[$k] -ne $after[$k])
        {
            echo "mod: ${k}: $($before[$k]) => $($after[$k])"
        }        
    }
    else{
        echo "add: ${k} => $($after[$k])"
    }
}

foreach($p in $afterPath)
{
    if($beforePath -Contains $p)
    {
        # echo "contain: ${p}"
        continue
    }

    echo "path: ${p}"
}