From fa6b786c9210638ee786b56ac338db106a103b1b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bartek=20Iwa=C5=84czuk?= <bartek@deno.com>
Date: Wed, 20 May 2026 13:53:12 +0200
Subject: [PATCH] feat: add POSIX null command (`:`) as a builtin

`:` is POSIX's null command: it discards its arguments and always
exits 0. Bash treats it as a builtin. We had `true` and `false`
already; add `:` alongside them (same `ExitCodeCommand(0)` underneath).

Without this, `deno task` for a `package.json` script defined as
`"test": ":"` (a common no-op pattern, e.g. used in the aube
benchmark fixture's ~1400-package project) fails with
`:: command not found` and exit code 127, while bash / sh / dash
all return 0 cleanly.

Adds an integration test covering the bare `:`, argument discarding,
and `&&` / `||` short-circuit behavior.
---
 src/shell/commands/mod.rs |  6 ++++++
 tests/integration_test.rs | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/src/shell/commands/mod.rs b/src/shell/commands/mod.rs
index 0c6dbdd..df3498e 100644
--- a/src/shell/commands/mod.rs
+++ b/src/shell/commands/mod.rs
@@ -98,6 +98,12 @@ pub fn builtin_commands() -> HashMap<String, Rc<dyn ShellCommand>> {
       "false".to_string(),
       Rc::new(ExitCodeCommand(1)) as Rc<dyn ShellCommand>,
     ),
+    // POSIX null command: discards its arguments and always exits 0.
+    // Commonly seen as `"test": ":"` in package.json no-op scripts.
+    (
+      ":".to_string(),
+      Rc::new(ExitCodeCommand(0)) as Rc<dyn ShellCommand>,
+    ),
     (
       "unset".to_string(),
       Rc::new(unset::UnsetCommand) as Rc<dyn ShellCommand>,
diff --git a/tests/integration_test.rs b/tests/integration_test.rs
index 2a8f905..a471bdc 100644
--- a/tests/integration_test.rs
+++ b/tests/integration_test.rs
@@ -154,6 +154,24 @@ async fn boolean_logic() {
     .await;
 }
 
+#[tokio::test]
+async fn null_command() {
+  // POSIX `:` is the null command — always succeeds, discards args.
+  TestBuilder::new().command(":").run().await;
+
+  TestBuilder::new()
+    .command(": ignored args && echo ok")
+    .assert_stdout("ok\n")
+    .run()
+    .await;
+
+  TestBuilder::new()
+    .command(": && echo yes || echo no")
+    .assert_stdout("yes\n")
+    .run()
+    .await;
+}
+
 #[tokio::test]
 async fn exit() {
   TestBuilder::new()