fix(message): reject empty bodies

src/main.rs

@@ -2599,17 +2599,21 @@ fn resolve_message_inbox(root: &Path, id: &str, host: &str) -> Result<PathBuf> {
 
 /// Body from `-m`, else stdin (so `st2 message send x < file` works).
 fn body_or_stdin(body: Option<String>) -> Result<String> {
-    match body {
-        Some(b) => Ok(b),
+    let body = match body {
+        Some(body) => body,
         None => {
             use std::io::Read as _;
-            let mut s = String::new();
+            let mut body = String::new();
             std::io::stdin()
-                .read_to_string(&mut s)
+                .read_to_string(&mut body)
                 .context("reading message body from stdin")?;
-            Ok(s)
+            body
         }
+    };
+    if body.is_empty() {
+        anyhow::bail!("message body must not be empty");
     }
+    Ok(body)
 }
 
 /// `[identity] <filename>` positionals: if `second` is present, `first` is the identity; otherwise

tests/message_cli.rs

@@ -79,6 +79,35 @@ fn sent(root: &Path, identity: &str, extra: &[&str]) -> std::process::Output {
         .unwrap()
 }
 
+#[test]
+fn send_rejects_empty_explicit_and_stdin_bodies_without_persisting_a_message() {
+    for body_arg in [Some(""), None] {
+        let tmp = tempfile::tempdir().unwrap();
+        write_agent(tmp.path(), "sender");
+        write_agent(tmp.path(), "recipient");
+
+        let mut command = Command::new(env!("CARGO_BIN_EXE_st2"));
+        command
+            .args(["message", "send", "recipient", "--root"])
+            .arg(tmp.path())
+            .args(["--host", "h", "--as", "sender"])
+            .stdin(Stdio::null());
+        if let Some(body) = body_arg {
+            command.args(["-m", body]);
+        }
+
+        let output = command.output().unwrap();
+        assert!(!output.status.success());
+        assert!(
+            String::from_utf8_lossy(&output.stderr).contains("message body must not be empty"),
+            "{}",
+            String::from_utf8_lossy(&output.stderr)
+        );
+        assert!(!tmp.path().join("h/recipient/resources").exists());
+        assert!(!tmp.path().join("h/sender/resources").exists());
+    }
+}
+
 #[test]
 fn event_metadata_is_exposed_by_list_and_read_json() {
     let tmp = tempfile::tempdir().unwrap();