Merge pull request #4171 from insky7/main

Add support for array_to_string and array_to_string_null array functions

diesel/src/pg/expression/functions.rs

@@ -865,3 +865,96 @@ define_sql_function! {
     /// ```
     fn array_remove<Arr: ArrayOrNullableArray<Inner=T> + SingleValue, T: SingleValue>(a: Arr, e: T) -> Arr;
 }
+
+#[cfg(feature = "postgres_backend")]
+define_sql_function! {
+    /// Converts each array element to its text representation and concatenates those elements
+    /// separated by the delimiter string. If `null_string` is provided and is not `NULL`, then `NULL`
+    /// array entries are represented by that string; otherwise, they are omitted.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # include!("../../doctest_setup.rs");
+    /// #
+    /// # fn main() {
+    /// #     run_test().unwrap();
+    /// # }
+    /// #
+    /// # fn run_test() -> QueryResult<()> {
+    /// #     use diesel::dsl::array_to_string_with_null_string;
+    /// #     use diesel::sql_types::{Nullable, Text, Array};
+    /// #     let connection = &mut establish_connection();
+    ///
+    /// // Example with `NULL` representation as a string
+    /// let result: String = diesel::select(array_to_string_with_null_string::<Array<Nullable<Text>>, _, _, _>(
+    ///     vec![Some("first"), None::<&str>, Some("third")], ",", "NULL"))
+    ///     .get_result(connection)?;
+    /// assert_eq!(result, "first,NULL,third");
+    ///
+    /// // Example without any `NULL` values
+    /// let result: String = diesel::select(array_to_string_with_null_string::<Array<Nullable<Text>>, _, _, _>(
+    ///     vec![Some("first"), Some("second")], ",", "NULL"))
+    ///     .get_result(connection)?;
+    /// assert_eq!(result, "first,second");
+    ///
+    /// // Example with all `NULL` values
+    /// let result: String = diesel::select(array_to_string_with_null_string::<Array<Nullable<Text>>, _, _, _>(
+    ///     vec![None::<&str>, None::<&str>], ",", "NULL"))
+    ///     .get_result(connection)?;
+    /// assert_eq!(result, "NULL,NULL");
+    ///
+    /// #     Ok(())
+    /// # }
+    /// ```
+    #[sql_name = "array_to_string"]
+    fn array_to_string_with_null_string<Arr: ArrayOrNullableArray + SingleValue>(
+        array: Arr, del: Text, null: Text
+    ) -> Text;
+}
+
+#[cfg(feature = "postgres_backend")]
+define_sql_function! {
+    /// Converts each array element to its text representation and concatenates those elements
+    /// separated by the delimiter string. `NULL` entries are omitted in this variant.
+    /// See [array_to_string_with_null_string] for a variant with that argument.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # include!("../../doctest_setup.rs");
+    /// #
+    /// # fn main() {
+    /// #     run_test().unwrap();
+    /// # }
+    /// #
+    /// # fn run_test() -> QueryResult<()> {
+    /// #     use diesel::dsl::array_to_string;
+    /// #     use diesel::sql_types::{Text, Array, Nullable};
+    /// #     let connection = &mut establish_connection();
+    ///
+    /// // Example with non-null values
+    /// let result: String = diesel::select(array_to_string::<Array<Nullable<Text>>, _, _>(
+    ///     vec![Some("first"), Some("second")], ","))
+    ///     .get_result(connection)?;
+    /// assert_eq!(result, "first,second");
+    ///
+    /// // Example with `NULL` values (omitted in the result)
+    /// let result: String = diesel::select(array_to_string::<Array<Nullable<Text>>, _, _>(
+    ///     vec![Some("first"), None::<&str>, Some("third")], ","))
+    ///     .get_result(connection)?;
+    /// assert_eq!(result, "first,third");
+    ///
+    /// // Example with only `NULL` values (empty result)
+    /// let result: String = diesel::select(array_to_string::<Array<Nullable<Text>>, _, _>(
+    ///     vec![None::<&str>, None::<&str>], ","))
+    ///     .get_result(connection)?;
+    /// assert_eq!(result, "");
+    ///
+    /// #     Ok(())
+    /// # }
+    /// ```
+    fn array_to_string<Arr: ArrayOrNullableArray + SingleValue>(
+        array: Arr, del: Text
+    ) -> Text;
+}

diesel/src/pg/expression/helper_types.rs

@@ -308,6 +308,26 @@ 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_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_with_null_string<A, D, N> =
+    super::functions::array_to_string_with_null_string<
+        SqlTypeOf<A>, // The SQL type of the array
+        A,            // The array itself
+        D,            // The delimiter
+        N,            // The null string
+    >;
+
+/// 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<A, D> = super::functions::array_to_string<
+    SqlTypeOf<A>, // The SQL type of the array
+    A,            // The array itself
+    D,            // The delimiter
+>;
+
 /// Return type of [`lower(range)`](super::functions::lower())
 #[allow(non_camel_case_types)]
 #[cfg(feature = "postgres_backend")]

diesel_derives/tests/auto_type.rs

@@ -51,6 +51,7 @@ table! {
         range -> Range<Integer>,
         multirange -> Multirange<Integer>,
         timestamptz -> Timestamptz,
+        name -> Text
     }
 }
 
@@ -417,6 +418,8 @@ fn postgres_functions() -> _ {
         array_dims(pg_extras::array),
         array_prepend(pg_extras::id, pg_extras::array),
         array_remove(pg_extras::array, pg_extras::id),
+        array_to_string(pg_extras::array, pg_extras::name),
+        array_to_string_with_null_string(pg_extras::array, pg_extras::name, pg_extras::name),
     )
 }