[containers-shared] Fix Docker spawn opening console windows on Windows

On Windows, `detached: true` in child_process.spawn() gives each child
process its own visible console window. This caused many windows to flash
open during `wrangler deploy` with `[[containers]]` configured.

- Set `detached` conditionally: true on Unix (for process group cleanup),
  false on Windows (to prevent console windows)
- Add `windowsHide: true` to further suppress console windows on Windows
- Guard `process.kill(-pid)` abort logic: use `child.kill()` on Windows
  since negative-PID process group kill is Unix-only

Fixes #12963

Author: petebacondarwin

.changeset/fix-windows-docker-console-windows.md

@@ -0,0 +1,7 @@
+---
+"wrangler": patch
+---
+
+fix: prevent Docker container builds from spawning console windows on Windows
+
+On Windows, `detached: true` in `child_process.spawn()` gives each child process its own visible console window, causing many windows to flash open during `wrangler deploy` with `[[containers]]`. The `detached` option is now only set on non-Windows platforms (where it is needed for process group cleanup), and `windowsHide: true` is added to further suppress console windows on Windows.

packages/containers-shared/src/build.ts

@@ -58,9 +58,14 @@ export function dockerBuild(
 	const child = spawn(dockerPath, options.buildCmd, {
 		stdio: ["pipe", "inherit", "inherit"],
 		// We need to set detached to true so that the child process
-		// will control all of its child processed and we can kill
-		// all of them in case we need to abort the build process
-		detached: true,
+		// will control all of its child processes and we can kill
+		// all of them in case we need to abort the build process.
+		// On Windows, detached: true opens a new console window per child
+		// process, so we only set it on non-Windows platforms.
+		detached: process.platform !== "win32",
+		// Prevent child processes from opening visible console windows on Windows.
+		// This is a no-op on non-Windows platforms.
+		windowsHide: true,
 	});
 	if (child.stdin !== null) {
 		child.stdin.write(options.dockerfile);
@@ -85,8 +90,15 @@ export function dockerBuild(
 		abort: () => {
 			child.unref();
 			if (child.pid !== undefined) {
-				// kill run on the negative PID kills the whole group controlled by the child process
-				process.kill(-child.pid);
+				if (process.platform === "win32") {
+					// On Windows, negative-PID process group kill is not supported.
+					// Kill the child process directly instead.
+					child.kill();
+				} else {
+					// Kill using the negative PID to terminate the whole process group
+					// controlled by the child process.
+					process.kill(-child.pid);
+				}
 			}
 		},
 		ready,

packages/containers-shared/src/utils.ts

@@ -26,9 +26,14 @@ export const runDockerCmd = (
 	const child = spawn(dockerPath, args, {
 		stdio: stdio ?? "inherit",
 		// We need to set detached to true so that the child process
-		// will control all of its child processed and we can kill
-		// all of them in case we need to abort the build process
-		detached: true,
+		// will control all of its child processes and we can kill
+		// all of them in case we need to abort the build process.
+		// On Windows, detached: true opens a new console window per child
+		// process, so we only set it on non-Windows platforms.
+		detached: process.platform !== "win32",
+		// Prevent child processes from opening visible console windows on Windows.
+		// This is a no-op on non-Windows platforms.
+		windowsHide: true,
 	});
 	let errorHandled = false;
 
@@ -51,8 +56,15 @@ export const runDockerCmd = (
 			aborted = true;
 			child.unref();
 			if (child.pid !== undefined) {
-				// kill run on the negative PID kills the whole group controlled by the child process
-				process.kill(-child.pid);
+				if (process.platform === "win32") {
+					// On Windows, negative-PID process group kill is not supported.
+					// Kill the child process directly instead.
+					child.kill();
+				} else {
+					// Kill using the negative PID to terminate the whole process group
+					// controlled by the child process.
+					process.kill(-child.pid);
+				}
 			}
 		},
 		ready,