added support for json_strip_nulls and jsonb_strip_nulls

diesel/src/pg/expression/expression_methods.rs

@@ -3552,6 +3552,10 @@ pub(in crate::pg) mod private {
     impl JsonbOrNullableJsonb for Jsonb {}
     impl JsonbOrNullableJsonb for Nullable<Jsonb> {}
 
+    #[diagnostic::on_unimplemented(
+        message = "`{Self}` is neither `diesel::sql_types::Json` nor `diesel::sql_types::Nullable<Json>`",
+        note = "try to provide an expression that produces one of the expected sql types"
+    )]
     pub trait JsonOrNullableJson {}
 
     impl JsonOrNullableJson for Json {}

diesel/src/pg/expression/functions.rs

@@ -1850,3 +1850,92 @@ define_sql_function! {
     /// ```
     fn jsonb_pretty<E: JsonbOrNullableJsonb + SingleValue + MaybeNullableValue<Text>>(e: E) -> E::Out;
 }
+
+define_sql_function! {
+    /// Deletes all object fields that have null values from the given JSON value, recursively.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # include!("../../doctest_setup.rs");
+    /// #
+    /// # fn main() {
+    /// #     run_test().unwrap();
+    /// # }
+    /// #
+    /// # fn run_test() -> QueryResult<()> {
+    /// #     use diesel::dsl::json_strip_nulls;
+    /// #     use diesel::sql_types::{Json, Nullable};
+    /// #     use serde_json::{json, Value};
+    /// #     let connection = &mut establish_connection();
+    ///
+    /// let result = diesel::select(json_strip_nulls::<Json, _>(json!({"hello": null})))
+    ///     .get_result::<Value>(connection)?;
+    /// let expected: Value = json!({});
+    /// assert_eq!(result, expected);
+    ///
+    /// let result = diesel::select(json_strip_nulls::<Json, _>(json!([{"f1":1, "f2":null}, 2, null, 3])))
+    ///     .get_result::<Value>(connection)?;
+    /// let expected: Value = json!([{"f1":1}, 2, null, 3]);
+    /// assert_eq!(result, expected);
+    ///
+    /// let result = diesel::select(json_strip_nulls::<Nullable<Json>, _>(None::<Value>))
+    ///     .get_result::<Option<Value>>(connection)?;
+    /// assert!(result.is_none());
+    ///
+    /// let result = diesel::select(json_strip_nulls::<Json, _>(json!(null)))
+    ///     .get_result::<Value>(connection)?;
+    /// let expected = json!(null);
+    /// assert_eq!(result, expected);
+    ///
+    ///
+    /// #     Ok(())
+    /// # }
+    /// ```
+    fn json_strip_nulls<E: JsonOrNullableJson + SingleValue>(json: E) -> E;
+}
+
+define_sql_function! {
+    /// Deletes all object fields that have null values from the given JSON value, recursively.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # include!("../../doctest_setup.rs");
+    /// #
+    /// # fn main() {
+    /// #     run_test().unwrap();
+    /// # }
+    /// #
+    /// # fn run_test() -> QueryResult<()> {
+    /// #     use diesel::dsl::jsonb_strip_nulls;
+    /// #     use diesel::sql_types::{Jsonb, Nullable};
+    /// #     use serde_json::{json, Value};
+    /// #     let connection = &mut establish_connection();
+    ///
+    /// let result = diesel::select(jsonb_strip_nulls::<Jsonb, _>(json!({"hello": null})))
+    ///     .get_result::<Value>(connection)?;
+    /// let expected: Value = json!({});
+    /// assert_eq!(result, expected);
+    ///
+    /// let result = diesel::select(jsonb_strip_nulls::<Jsonb, _>(json!([{"f1":1, "f2":null}, 2, null, 3])))
+    ///     .get_result::<Value>(connection)?;
+    /// let expected: Value = json!([{"f1":1}, 2, null, 3]);
+    /// assert_eq!(result, expected);
+    ///
+    /// let result = diesel::select(jsonb_strip_nulls::<Nullable<Jsonb>, _>(None::<Value>))
+    ///     .get_result::<Option<Value>>(connection)?;
+    /// assert!(result.is_none());
+    ///
+    /// let result = diesel::select(jsonb_strip_nulls::<Jsonb, _>(json!(null)))
+    ///     .get_result::<Value>(connection)?;
+    /// let expected = json!(null);
+    /// assert_eq!(result, expected);
+    ///
+    ///
+    ///
+    /// #     Ok(())
+    /// # }
+    /// ```
+    fn jsonb_strip_nulls<E: JsonbOrNullableJsonb + SingleValue>(jsonb: E) -> E;
+}

diesel/src/pg/expression/helper_types.rs

@@ -501,3 +501,13 @@ pub type jsonb_typeof<E> = super::functions::jsonb_typeof<SqlTypeOf<E>, E>;
 #[allow(non_camel_case_types)]
 #[cfg(feature = "postgres_backend")]
 pub type jsonb_pretty<E> = super::functions::jsonb_pretty<SqlTypeOf<E>, E>;
+
+/// Return type of [`json_strip_nulls(json)`](super::functions::json_strip_nulls())
+#[allow(non_camel_case_types)]
+#[cfg(feature = "postgres_backend")]
+pub type json_strip_nulls<E> = super::functions::json_strip_nulls<SqlTypeOf<E>, E>;
+
+/// Return type of [`jsonb_strip_nulls(jsonb)`](super::functions::jsonb_strip_nulls())
+#[allow(non_camel_case_types)]
+#[cfg(feature = "postgres_backend")]
+pub type jsonb_strip_nulls<E> = super::functions::jsonb_strip_nulls<SqlTypeOf<E>, E>;

diesel_derives/tests/auto_type.rs

@@ -441,6 +441,8 @@ fn postgres_functions() -> _ {
         json_typeof(pg_extras::json),
         jsonb_typeof(pg_extras::jsonb),
         jsonb_pretty(pg_extras::jsonb),
+        json_strip_nulls(pg_extras::json),
+        jsonb_strip_nulls(pg_extras::jsonb),
     )
 }