fix(node/child_process): properly normalize stdio for 'spawnSync' (#21103)

Closes https://github.com/denoland/deno/issues/20782

2 files changed, 22 insertions, 3 deletions

diff --git a/cli/tests/unit_node/child_process_test.ts b/cli/tests/unit_node/child_process_test.ts
index 8d1c9a6b7..47e87096e 100644
--- a/cli/tests/unit_node/child_process_test.ts
+++ b/cli/tests/unit_node/child_process_test.ts
@@ -707,3 +707,17 @@ Deno.test(function spawnSyncUndefinedValueInEnvVar() {
   assertEquals(ret.status, 0);
   assertEquals(ret.stdout.toString("utf-8").trim(), "BAZ");
 });
+
+Deno.test(function spawnSyncStdioUndefined() {
+  const ret = spawnSync(
+    `"${Deno.execPath()}" eval "console.log('hello');console.error('world')"`,
+    {
+      stdio: [undefined, undefined, undefined],
+      shell: true,
+    },
+  );
+
+  assertEquals(ret.status, 0);
+  assertEquals(ret.stdout.toString("utf-8").trim(), "hello");
+  assertEquals(ret.stderr.toString("utf-8").trim(), "world");
+});
diff --git a/ext/node/polyfills/internal/child_process.ts b/ext/node/polyfills/internal/child_process.ts
index 33b0b3166..7d707758e 100644
--- a/ext/node/polyfills/internal/child_process.ts
+++ b/ext/node/polyfills/internal/child_process.ts
@@ -835,7 +835,12 @@ export function spawnSync(
     maxBuffer,
     windowsVerbatimArguments = false,
   } = options;
-  const normalizedStdio = normalizeStdioOption(stdio);
+  const [
+    _stdin_ = "pipe", // TODO(bartlomieju): use this?
+    stdout_ = "pipe",
+    stderr_ = "pipe",
+    _channel, // TODO(kt3k): handle this correctly
+  ] = normalizeStdioOption(stdio);
   [command, args] = buildCommand(command, args ?? [], shell);
 
   const result: SpawnSyncResult = {};
@@ -844,8 +849,8 @@ export function spawnSync(
       args,
       cwd,
       env: mapValues(env, (value) => value.toString()),
-      stdout: toDenoStdio(normalizedStdio[1]),
-      stderr: toDenoStdio(normalizedStdio[2]),
+      stdout: toDenoStdio(stdout_),
+      stderr: toDenoStdio(stderr_),
       uid,
       gid,
       windowsRawArguments: windowsVerbatimArguments,