ci(windows): stash multi-line env vars around Enter-VsDevShell

scripts/vs-shell.ps1

@@ -33,6 +33,17 @@ if($env:VSINSTALLDIR -eq $null) {
     }
   }
 
+  # Enter-VsDevShell parses cmd.exe `set` output line by line, so a multi-line
+  # value (e.g. BUILDKITE_MESSAGE) leaks each `KEY=VALUE`-shaped body line as a
+  # real env var. Stash multi-line vars around the loader to keep them intact.
+  $multilineEnv = @{}
+  foreach ($item in (Get-ChildItem env:)) {
+    if ($item.Value -match "[\r\n]") {
+      $multilineEnv[$item.Name] = $item.Value
+      Remove-Item -LiteralPath "env:$($item.Name)"
+    }
+  }
+
   Push-Location $vsDir
   try {
     $vsShell = (Join-Path -Path $vsDir -ChildPath "Common7\Tools\Launch-VsDevShell.ps1")
@@ -47,6 +58,9 @@ if($env:VSINSTALLDIR -eq $null) {
     }
   } finally {
     Pop-Location
+    foreach ($name in $multilineEnv.Keys) {
+      Set-Item -LiteralPath "env:$name" -Value $multilineEnv[$name]
+    }
   }
 }
 

test/internal/vs-shell-multiline-env.test.ts

@@ -0,0 +1,60 @@
+// Regression guard for scripts/vs-shell.ps1: Enter-VsDevShell parses
+// `cmd /c set` output line by line, so a multi-line env value (e.g. the
+// commit message in BUILDKITE_MESSAGE) used to leak each `KEY=VALUE`-shaped
+// body line as its own env var. A body line like `BUN_JSC_foo=bar baz` then
+// aborted every spawned Bun process on the Windows test lanes.
+import { expect, test } from "bun:test";
+import { bunEnv, bunExe, isWindows } from "harness";
+import { existsSync } from "node:fs";
+import { join } from "node:path";
+
+const vswhere = "C:\\Program Files (x86)\\Microsoft Visual Studio\\Installer\\vswhere.exe";
+
+test.skipIf(!isWindows || !existsSync(vswhere))(
+  "vs-shell.ps1 shields multi-line env vars from Enter-VsDevShell",
+  async () => {
+    const repoRoot = join(import.meta.dir, "..", "..");
+    const vsShell = join(repoRoot, "scripts", "vs-shell.ps1");
+    const probe = ["line1", "VS_SHELL_LEAKED=oops", "BUN_JSC_notARealOption=1 some trailing text", "line4"].join("\n");
+
+    const dump =
+      "process.stdout.write(JSON.stringify({" +
+      "probe:process.env.VS_SHELL_PROBE," +
+      "leaked:process.env.VS_SHELL_LEAKED," +
+      "jsc:process.env.BUN_JSC_notARealOption," +
+      "vs:process.env.VSINSTALLDIR" +
+      "}))";
+
+    const env: Record<string, string | undefined> = { ...bunEnv, VS_SHELL_PROBE: probe };
+    // The Windows test runner already sits inside vs-shell.ps1, so VSINSTALLDIR
+    // is set; unset it so the child re-runs the loader and hits the stash path.
+    delete env.VSINSTALLDIR;
+
+    await using proc = Bun.spawn({
+      cmd: ["pwsh", "-NoProfile", "-File", vsShell, bunExe(), "-e", dump],
+      env,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+    const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+    // vs-shell.ps1 writes status lines before `$ <cmd>`; the JSON is the last line.
+    const jsonLine = stdout.trimEnd().split("\n").pop() ?? "";
+    let result: { probe: unknown; leaked: unknown; jsc: unknown; vs: unknown };
+    try {
+      result = JSON.parse(jsonLine);
+    } catch {
+      throw new Error(`expected JSON on last line, got:\n--- stdout ---\n${stdout}\n--- stderr ---\n${stderr}`);
+    }
+
+    expect(result).toEqual({
+      probe, // round-tripped intact, newlines preserved
+      leaked: undefined, // body line did not become its own var
+      jsc: undefined, // body line did not become its own var
+      vs: expect.any(String), // VS env was still loaded
+    });
+    expect(stderr).not.toContain("invalid JSC environment variable");
+    expect(exitCode).toBe(0);
+  },
+  60_000,
+);