chore: #2125 change news blurb and fix deprecation messaging

NEWS.md

@@ -6,8 +6,6 @@
 
 - `derive_extreme_records()`, `derive_var_extreme_flag()`,`derive_vars_joined()` and `derive_vars_merged()` were enhanced with the arguments `true_value` and `false_value` to align with preexisting functions that had similar functionality (#2125)
 
-- The default value for the `false_value` argument in `derive_extreme_records()` was changed to `NA_character_` (#2125)
-
 - `restrict_derivation()` now allows `{dplyr}` functions like `mutate` in the `derivation argument (#2143)
 
 - `derive_summary_records()`, `derive_var_merged_summary()`, and `get_summary_records()`
@@ -28,6 +26,8 @@ were enhanced such that more than one summary variable can be derived, e.g.,
 
 - For the function `derive_vars_merged()`, the argument `match_flag` was renamed to `exist_flag` (#2125)
 
+- The default value for the `false_value` argument in `derive_extreme_records()` was changed to `NA_character_` (#2125)
+
 - The following functions, which were deprecated in previous `{admiral}` versions, have been removed: (#2098)
   - `derive_param_extreme_event()`
   - `derive_vars_last_dose()`

R/derive_merged.R

@@ -307,7 +307,7 @@ derive_vars_merged <- function(dataset,
                                new_vars = NULL,
                                filter_add = NULL,
                                mode = NULL,
-                               match_flag = NULL,
+                               match_flag,
                                exist_flag = NULL,
                                true_value = "Y",
                                false_value = NA_character_,
@@ -329,11 +329,11 @@ derive_vars_merged <- function(dataset,
       extract_vars(new_vars)
     )
   )
-  if (!is.null(match_flag)) {
+  if (!is_missing(match_flag)) {
     deprecate_warn(
       "1.0.0",
-      "derive_vars_merged(old_param = 'match_flag')",
-      "derive_vars_merged(new_param = 'exist_flag')"
+      "derive_vars_merged(match_flag =)",
+      "derive_vars_merged(exist_flag =)"
     )
     exist_flag <- assert_symbol(enexpr(match_flag), optional = TRUE)
   }