Fix Windows-only cmd /c calls in build_web.ps1 to support Linux

[Copilot]

build_web.ps1 used cmd /c to invoke the compiler and linker, which fails on Linux where cmd.exe doesn't exist. The script also hardcoded a Windows backslash path separator in Join-Path.

Changes

• Cross-platform Join-Path — replaced "upstream\emscripten\emcc.py" string with multi-argument Join-Path $env:EMSDK "upstream" "emscripten" "emcc.py" so PowerShell resolves the separator per OS

• Compile step — replaced cmd /c "... > tmpOut 2>&1" with Start-Process -FilePath $env:EMSDK_PYTHON -ArgumentList @("-E", $emccPy, "@$rspFull") -RedirectStandardOutput ... -RedirectStandardError ... -PassThru; exit code checked via $proc.ExitCode instead of $LASTEXITCODE

• Link step — replaced cmd /c "emcc @$linkRsp" with & emcc "@$linkRsp"; $LASTEXITCODE is set correctly by PowerShell for external executable invocations

# Before
$emccPy = Join-Path $env:EMSDK "upstream\emscripten\emcc.py"
cmd /c "`"$env:EMSDK_PYTHON`" -E `"$emccPy`" @`"$rspFull`" > `"$tmpOut`" 2>&1"
# ...
cmd /c "emcc @$linkRsp"

# After
$emccPy = Join-Path $env:EMSDK "upstream" "emscripten" "emcc.py"
$proc = Start-Process -FilePath $env:EMSDK_PYTHON -ArgumentList @("-E", $emccPy, "@$rspFull") `
    -NoNewWindow -Wait -RedirectStandardOutput $tmpOut -RedirectStandardError $tmpErr -PassThru
# ...
& emcc "@$linkRsp"

Original prompt

Problem

The file web-build/project/emscripten/build_web.ps1 uses cmd /c (Windows Command Prompt) to invoke emcc on lines 91 and 113. This fails on Linux because cmd doesn't exist there. The user is running on Linux (/home/admin1/MCPE-WASM/...) with PowerShell Core installed.

The errors look like:

cmd: /home/admin1/MCPE-WASM/web-build/project/emscripten/build_web.ps1:91
Line |
  91 |          cmd /c "`"$env:EMSDK_PYTHON`" -E `"$emccPy`" @`"$rspFull`" >  …
     |          ~~~
     | The term 'cmd' is not recognized as a name of a cmdlet, function, script
     | file, or executable program.

And similarly on line 113:

Line |
 113 |  cmd /c "emcc @$linkRsp"
     |  ~~~
     | The term 'cmd' is not recognized as a name of a cmdlet, function, script
     | file, or executable program.

Required Fix

Replace the Windows-specific cmd /c invocations with cross-platform PowerShell equivalents that work on both Windows and Linux:

Line 88 — Fix the emsdk path separator

# Change from Windows backslash:
$emccPy = Join-Path $env:EMSDK "upstream\emscripten\emcc.py"
# To cross-platform:
$emccPy = Join-Path $env:EMSDK "upstream" "emscripten" "emcc.py"

Lines 89-96 — Replace the compile cmd /c block

The current code:

$tmpOut = [System.IO.Path]::GetTempFileName()
$rspFull = (Resolve-Path $rspFile).Path
cmd /c "`"$env:EMSDK_PYTHON`" -E `"$emccPy`" @`"$rspFull`" > `"$tmpOut`" 2>&1"
$output = Get-Content $tmpOut -Raw
Remove-Item $tmpOut -Force -ErrorAction SilentlyContinue
if ($LASTEXITCODE -ne 0) {
    $errors += @{ "file" = $srcFile; "output" = $output }
}

Should be replaced with a cross-platform approach using Start-Process or direct invocation with & $env:EMSDK_PYTHON -E $emccPy @args and redirecting output, or simply using & emcc directly since emsdk_env.ps1 should put emcc on the PATH. A good approach:

$rspFull = (Resolve-Path $rspFile).Path
$tmpOut = [System.IO.Path]::GetTempFileName()
$procArgs = @("-E", $emccPy, "@$rspFull")
$proc = Start-Process -FilePath $env:EMSDK_PYTHON -ArgumentList $procArgs -NoNewWindow -Wait -RedirectStandardOutput $tmpOut -RedirectStandardError "$tmpOut.err" -PassThru
$output = ""
if (Test-Path $tmpOut) { $output += Get-Content $tmpOut -Raw -ErrorAction SilentlyContinue }
if (Test-Path "$tmpOut.err") { $output += Get-Content "$tmpOut.err" -Raw -ErrorAction SilentlyContinue }
Remove-Item $tmpOut, "$tmpOut.err" -Force -ErrorAction SilentlyContinue
if ($proc.ExitCode -ne 0) {
    $errors += @{ "file" = $srcFile; "output" = $output }
}

Line 113 — Replace the link cmd /c

The current code:

cmd /c "emcc @$linkRsp"

Should become:

& emcc "@$linkRsp"

Or if emcc is not directly on PATH, use the Python approach:

$emccPy = Join-Path $env:EMSDK "upstream" "emscripten" "emcc.py"
& $env:EMSDK_PYTHON -E $emccPy "@$linkRsp"

Important Notes

• The fix must work on BOTH Windows and Linux (cross-platform PowerShell).
• Join-Path with multiple arguments is cross-platform and handles path separators automatically.
• Do NOT break the existing response-file (@file) argument passing to emcc.
• The $ErrorActionPreference = "Continue" at the top of the file should remain.
• Test that $LASTEXITCODE is still properly captured after the changes.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: how do i test this branch and test deploy it on localhost?

Assistant:

Let me look at the repository structure and the PR to understand how this project is set up.

Assistant: Here's a complete guide to testing this PR branch locally and serving it on localhost:

---

Step 1: Clone the repo and check out the PR branch

git clone https://github.com/sriail/MCPE-WASM.git
cd MCPE-WASM
git checkout copilot/copy-mcpe-assets-to-web-build

Or if you already have the repo cloned:

git fetch origin
git checkout copilot/copy-mcpe-assets-to-web-build

---

Step 2: Prerequisites

You'll need these installed on your system:

• Git — to clone emsdk
• Python 3 — used by the Emscripten SDK
• PowerShell — the build scripts are all .ps1 (works on Windows natively; on macOS/Linux install PowerShell Core)

---

Step 3: Install the Emscripten SDK

From the web-build/ directory, run:

cd web-build
.\install_deps.ps1

This will:

1. Clone the Emscripten SDK into a sibling emsdk/ folder (next to web-build/)
2. Install and activate the latest Emscripten toolchain

Note: The first install takes several minutes as it downloads the LLVM/Clang toolchain.

---

Step 4: Build the WASM project

Still from web-build/, run:

.\build.ps1

This invokes `web-build/project/emscripten/build_w...

This pull request was created from Copilot chat.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.