Add support for array_to_string and array_to_string_null array functions

diesel/src/pg/expression/functions.rs

@@ -784,18 +784,18 @@ define_sql_function! {
     /// #     Ok(())
     /// # }
     /// ```
-    fn array_to_string_null<Arr: ArrayOrNullableArray<Inner=Elem> + SingleValue, Elem: SingleValue>(
+    #[sql_name = "array_to_string"]
+    fn array_to_string_with_null_string<Arr: ArrayOrNullableArray + SingleValue>(
         arr: Arr,
         delim: Text,
-        null_str: Nullable<Text>
+        null_str: Text
     ) -> Text;
 }
 
 #[cfg(feature = "postgres_backend")]
 define_sql_function! {
-    #[sql_name = "array_to_string"]
     /// Converts each array element to its text representation, and concatenates those separated by the delimiter string.
-    /// This variant omits the `null_str` argument.
+    /// This variant omits the `null_str` argument. See [array_to_string_null] for a variant with that argument
     /// # Example
     ///
     /// ```rust
@@ -810,15 +810,14 @@ define_sql_function! {
     /// #     let conn = &mut establish_connection();
     ///
     /// let result = diesel::select(array_to_string::<Array<Text>, Text>(
-    ///     vec!["a".to_string(), "b".to_string(), "c".to_string()],
-    ///     ", ".to_string()
+    ///     vec!["a", "b", "c"], ","
     /// )).get_result::<String>(conn)?;
     /// assert_eq!("a, b, c".to_string(), result);
     ///
     /// #     Ok(())
     /// # }
     /// ```
-    fn array_to_string<Arr: ArrayOrNullableArray<Inner=Elem> + SingleValue, Elem: SingleValue>(
+    fn array_to_string<Arr: ArrayOrNullableArray + SingleValue>(
         arr: Arr,
         delim: Text
     ) -> Text;

diesel/src/pg/expression/helper_types.rs

@@ -3,7 +3,7 @@ use crate::expression::grouped::Grouped;
 use crate::expression::Expression;
 use crate::pg::expression::expression_methods::private::{JsonIndex, JsonRemoveIndex};
 use crate::pg::types::sql_types::Array;
-use crate::sql_types::{Inet, Integer, Nullable, Text, VarChar};
+use crate::sql_types::{Inet, Integer, Text, VarChar};
 
 /// The return type of [`lhs.ilike(rhs)`](super::expression_methods::PgTextExpressionMethods::ilike)
 #[cfg(feature = "postgres_backend")]
@@ -308,22 +308,16 @@ pub type NotLikeBinary<Lhs, Rhs> = crate::dsl::NotLike<Lhs, Rhs>;
 #[deprecated(note = "Use `dsl::Concat` instead")]
 pub type ConcatArray<Lhs, Rhs> = crate::dsl::Concat<Lhs, Rhs>;
 
-/// Return type of [`array_to_string_null(arr, delim, null_str)`](super::functions::array_to_string_null())
+/// Return type of [`array_to_string_with_null_string(arr, delim, null_str)`](super::functions::array_to_string_with_null_string())
 #[allow(non_camel_case_types)]
 #[cfg(feature = "postgres_backend")]
-pub type array_to_string_null<Arr, Elem> = super::functions::array_to_string_null<
-    SqlTypeOf<Arr>,
-    SqlTypeOf<Elem>,
-    Arr,
-    Elem,
-    Nullable<Text>,
->;
+pub type array_to_string_with_null_string<Arr, Elem> =
+    super::functions::array_to_string_with_null_string<SqlTypeOf<Arr>, SqlTypeOf<Elem>, Arr, Text>;
 
 /// Return type of [`array_to_string(arr, delim)`](super::functions::array_to_string())
 #[allow(non_camel_case_types)]
 #[cfg(feature = "postgres_backend")]
-pub type array_to_string<Arr, Elem> =
-    super::functions::array_to_string<SqlTypeOf<Arr>, SqlTypeOf<Elem>, Arr, Elem>;
+pub type array_to_string<Arr> = super::functions::array_to_string<SqlTypeOf<Arr>, Arr, Text>;
 
 /// Return type of [`lower(range)`](super::functions::lower())
 #[allow(non_camel_case_types)]

diesel_derives/tests/auto_type.rs

@@ -411,7 +411,7 @@ fn postgres_functions() -> _ {
             bound,
         ),
         array_append(pg_extras::array, pg_extras::id),
-        array_to_string_null(pg_extras::array, ", ".into(), Some("NULL".into())),
+        array_to_string_with_null_string(pg_extras::array, ", ".into(), Some("NULL".into())),
         array_to_string(pg_extras::array, ", ".to_string()),
     )
 }