Implement stringutils::join_arguments.

src/utils/string_utils.cpp

@@ -27,5 +27,16 @@ std::string to_string(double value, const std::string& format_spec) {
     return fmt::format(format_spec, value);
 }
 
+std::string join_arguments(const std::string& lhs, const std::string& rhs) {
+    if (lhs.empty()) {
+        return rhs;
+    } else if (rhs.empty()) {
+        return lhs;
+    } else {
+        return fmt::format("{}", fmt::join({lhs, rhs}, ", "));
+    }
+}
+
+
 }  // namespace stringutils
 }  // namespace nmodl

src/utils/string_utils.hpp

@@ -210,6 +210,12 @@ static inline bool starts_with(const std::string& haystack, const std::string& n
  */
 std::string to_string(double value, const std::string& format_spec = "{:.16g}");
 
+/** Joint two (list of) arguments.
+ *
+ * The tricks is to not add a ',' when either side is empty.
+ */
+std::string join_arguments(const std::string& lhs, const std::string& rhs);
+
 /** \} */  // end of utils
 
 }  // namespace stringutils

test/unit/utils/string_utils.cpp

@@ -54,3 +54,21 @@ TEST_CASE("starts_with") {
         REQUIRE(!stringutils::starts_with("abcde", "abcde++"));
     }
 }
+
+TEST_CASE("join_arguments") {
+    SECTION("both empty") {
+        REQUIRE(stringutils::join_arguments("", "") == "");
+    }
+
+    SECTION("lhs emtpy") {
+        REQUIRE(stringutils::join_arguments("", "foo, bar") == "foo, bar");
+    }
+
+    SECTION("rhs empty") {
+        REQUIRE(stringutils::join_arguments("foo", "") == "foo");
+    }
+
+    SECTION("neither empty") {
+        REQUIRE(stringutils::join_arguments("foo", "bar") == "foo, bar");
+    }
+}