fix(hu-meter): escape --json topic output and document --raw in echo usage

Author: YuanYuYuan

crates/hiroz-union/plugins/hu-meter/src/lib.rs

@@ -182,7 +182,7 @@ impl HuMeter {
     fn cmd_echo(&mut self, args: &[String]) {
         let Some(topic) = args.first().cloned() else {
             render::println(
-                "Usage: hu meter echo <topic> [--count <n>] [--field <path>] [--timeout <s>]",
+                "Usage: hu meter echo <topic> [--count <n>] [--field <path>] [--timeout <s>] [--raw]",
             );
             render::exit(1);
             self.mode = Mode::Done;
@@ -295,8 +295,9 @@ impl HuMeter {
                         topics
                             .iter()
                             .map(|t| format!(
-                                "{{\"name\":\"{}\",\"type\":\"{}\"}}",
-                                t.name, t.type_name
+                                "{{\"name\":{},\"type\":{}}}",
+                                json_str(&t.name),
+                                json_str(&t.type_name)
                             ))
                             .collect::<Vec<_>>()
                             .join(",")
@@ -1236,6 +1237,13 @@ fn infer_param_value(s: &str) -> (u8, String) {
     (4, format!(r#""string_value":{quoted}"#))
 }
 
+/// Serialize a string as a JSON string literal (with surrounding quotes),
+/// escaping quotes, backslashes, and control characters so the emitted
+/// `--json` output stays valid JSON regardless of topic/type contents.
+fn json_str(s: &str) -> String {
+    serde_json::to_string(s).unwrap_or_else(|_| "\"\"".to_string())
+}
+
 /// Same as `infer_param_value` but from an already-typed JSON value (as
 /// produced by the host's YAML-file parser for `param load`), so a numeric
 /// YAML scalar like `55` isn't round-tripped through string parsing.