text.spelling.editDictionary: say each list entry must be a single word (part of #4936)

crates/engine/src/cmd/spelling.rs

@@ -370,9 +370,9 @@ fn word_list(p: &Value, key: &str, command: &str) -> Result<BTreeSet<String>> {
     words
         .iter()
         .map(|w| {
-            w.as_str().and_then(craft_proof::custom_word).ok_or_else(|| {
-                bad(command, format!("`{key}` must hold words of one word, at most {} characters", craft_proof::MAX_CUSTOM_WORD_CHARS))
-            })
+            w.as_str()
+                .and_then(craft_proof::custom_word)
+                .ok_or_else(|| bad(command, format!("`{key}` must hold single words of at most {} characters", craft_proof::MAX_CUSTOM_WORD_CHARS)))
         })
         .collect()
 }

crates/engine/src/tests/spelling.rs

@@ -291,6 +291,8 @@ fn a_dictionary_edit_is_saved_whole_or_not_at_all() {
         assert!(s.execute(EDIT, &p).is_err(), "{EDIT} refuses a bad list");
         assert!(in_dictionary(&mut s, "pqzvkb"), "{EDIT} changed nothing");
     }
+    let e = s.execute(EDIT, &json!({"add": ["a b"]})).unwrap_err().to_string();
+    assert!(e.contains("must hold single words of at most 64 characters"), "{e}");
     run(&mut s, EDIT, json!({"remove": ["pqzvkb", "pqzvkc"]}));
     assert!(!in_dictionary(&mut s, "pqzvkb") && !in_dictionary(&mut s, "pqzvkc"));
 }