feat(sqlite): add json_error_position fn

diesel/src/sqlite/expression/expression_methods.rs

@@ -2,7 +2,7 @@
 
 pub(in crate::sqlite) use self::private::{
     BinaryOrNullableBinary, JsonOrNullableJson, JsonOrNullableJsonOrJsonbOrNullableJsonb,
-    MaybeNullableValue, TextOrNullableText,
+    MaybeNullableValue, TextOrNullableText, TextOrNullableTextOrBinaryOrNullableBinary,
 };
 use super::operators::*;
 use crate::dsl;
@@ -108,6 +108,17 @@ pub(in crate::sqlite) mod private {
     impl BinaryOrNullableBinary for Binary {}
     impl BinaryOrNullableBinary for Nullable<Binary> {}
 
+    #[diagnostic::on_unimplemented(
+        message = "`{Self}` is neither `diesel::sql_types::Text`, `diesel::sql_types::Nullable<Text>`, `diesel::sql_types::Binary` nor `diesel::sql_types::Nullable<Binary>`",
+        note = "try to provide an expression that produces one of the expected sql types"
+    )]
+    pub trait TextOrNullableTextOrBinaryOrNullableBinary {}
+
+    impl TextOrNullableTextOrBinaryOrNullableBinary for Text {}
+    impl TextOrNullableTextOrBinaryOrNullableBinary for Nullable<Text> {}
+    impl TextOrNullableTextOrBinaryOrNullableBinary for Binary {}
+    impl TextOrNullableTextOrBinaryOrNullableBinary for Nullable<Binary> {}
+
     #[diagnostic::on_unimplemented(
         message = "`{Self}` is neither `diesel::sql_types::Json`, `diesel::sql_types::Jsonb`, `diesel::sql_types::Nullable<Json>` nor `diesel::sql_types::Nullable<Jsonb>`",
         note = "try to provide an expression that produces one of the expected sql types"

diesel/src/sqlite/expression/functions.rs

@@ -6,6 +6,7 @@ use crate::sqlite::expression::expression_methods::JsonOrNullableJson;
 use crate::sqlite::expression::expression_methods::JsonOrNullableJsonOrJsonbOrNullableJsonb;
 use crate::sqlite::expression::expression_methods::MaybeNullableValue;
 use crate::sqlite::expression::expression_methods::TextOrNullableText;
+use crate::sqlite::expression::expression_methods::TextOrNullableTextOrBinaryOrNullableBinary;
 
 #[cfg(feature = "sqlite")]
 #[declare_sql_function]
@@ -272,6 +273,113 @@ extern "SQL" {
         path: Text,
     ) -> Nullable<Integer>;
 
+    /// The json_error_position(X) function returns 0 if the input X is a well-formed JSON or JSON5 string.
+    /// If the input X contains one or more syntax errors, then this function returns the character position of the first syntax error.
+    /// The left-most character is position 1.
+    ///
+    /// If the input X is a BLOB, then this routine returns 0 if X is a well-formed JSONB blob. If the return value is positive,
+    /// then it represents the approximate 1-based position in the BLOB of the first detected error.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # include!("../../doctest_setup.rs");
+    /// #
+    /// # fn main() {
+    /// #     #[cfg(feature = "serde_json")]
+    /// #     run_test().unwrap();
+    /// # }
+    /// #
+    /// # #[cfg(feature = "serde_json")]
+    /// # fn run_test() -> QueryResult<()> {
+    /// #     use diesel::dsl::{sql, json_error_position};
+    /// #     use diesel::sql_types::{Binary, Text, Nullable};
+    /// #     let connection = &mut establish_connection();
+    ///
+    /// let version = diesel::select(sql::<Text>("sqlite_version();"))
+    ///         .get_result::<String>(connection)?;
+    ///
+    /// // Querying SQLite version should not fail.
+    /// let version_components: Vec<&str> = version.split('.').collect();
+    /// let major: u32 = version_components[0].parse().unwrap();
+    /// let minor: u32 = version_components[1].parse().unwrap();
+    /// let patch: u32 = version_components[2].parse().unwrap();
+    ///
+    /// if major > 3 || (major == 3 && minor >= 46) {
+    ///     /* Valid sqlite version, do nothing */
+    /// } else {
+    ///     println!("SQLite version is too old, skipping the test.");
+    ///     return Ok(());
+    /// }
+    ///
+    /// let result = diesel::select(json_error_position::<Text, _>(r#"{"a": "b", "c": 1}"#))
+    ///     .get_result::<i32>(connection)?;
+    ///
+    /// assert_eq!(0, result);
+    ///
+    /// let result = diesel::select(json_error_position::<Text, _>(r#"{"a": b", "c": 1}"#))
+    ///     .get_result::<i32>(connection)?;
+    ///
+    /// assert_eq!(7, result);
+    ///
+    /// let json5 = r#"
+    ///     {
+    ///         // A traditional message.
+    ///         message: 'hello world',
+    ///
+    ///         // A number for some reason.
+    ///         n: 42,
+    ///     }
+    /// "#;
+    /// let result = diesel::select(json_error_position::<Text, _>(json5))
+    ///     .get_result::<i32>(connection)?;
+    ///
+    /// assert_eq!(0, result);
+    ///
+    /// let json5_with_error = r#"
+    ///     {
+    ///         // A traditional message.
+    ///         message: hello world',
+    ///
+    ///         // A number for some reason.
+    ///         n: 42,
+    ///     }
+    /// "#;
+    /// let result = diesel::select(json_error_position::<Text, _>(json5_with_error))
+    ///     .get_result::<i32>(connection)?;
+    ///
+    /// assert_eq!(59, result);
+    ///
+    /// let result = diesel::select(json_error_position::<Nullable<Text>, _>(None::<&str>))
+    ///     .get_result::<Option<i32>>(connection)?;
+    ///
+    /// assert_eq!(None, result);
+    ///
+    /// let result = diesel::select(json_error_position::<Binary, _>(br#"{"a": "b", "c": 1}"#))
+    ///     .get_result::<i32>(connection)?;
+    ///
+    /// assert_eq!(0, result);
+    ///
+    /// let result = diesel::select(json_error_position::<Binary, _>(br#"{"a": b", "c": 1}"#))
+    ///     .get_result::<i32>(connection)?;
+    ///
+    /// assert_eq!(7, result);
+    ///
+    /// let result = diesel::select(json_error_position::<Nullable<Binary>, _>(None::<Vec<u8>>))
+    ///     .get_result::<Option<i32>>(connection)?;
+    ///
+    /// assert_eq!(None, result);
+    ///
+    /// #     Ok(())
+    /// # }
+    /// ```
+    #[cfg(feature = "sqlite")]
+    fn json_error_position<
+        X: TextOrNullableTextOrBinaryOrNullableBinary + MaybeNullableValue<Integer>,
+    >(
+        x: X,
+    ) -> X::Out;
+
     /// Converts the given json value to pretty-printed, indented text
     ///
     /// # Example

diesel/src/sqlite/expression/helper_types.rs

@@ -28,6 +28,11 @@ pub type json_array_length<J> = super::functions::json_array_length<SqlTypeOf<J>
 pub type json_array_length_with_path<J, P> =
     super::functions::json_array_length_with_path<SqlTypeOf<J>, J, P>;
 
+/// Return type of [`json_error_position(json)`](super::functions::json_error_position())
+#[allow(non_camel_case_types)]
+#[cfg(feature = "sqlite")]
+pub type json_error_position<X> = super::functions::json_error_position<SqlTypeOf<X>, X>;
+
 /// Return type of [`json_pretty(json)`](super::functions::json_pretty())
 #[allow(non_camel_case_types)]
 #[cfg(feature = "sqlite")]

diesel_derives/tests/auto_type.rs

@@ -507,6 +507,8 @@ fn sqlite_functions() -> _ {
         jsonb(sqlite_extras::blob),
         json_array_length(sqlite_extras::json),
         json_array_length_with_path(sqlite_extras::json, sqlite_extras::text),
+        json_error_position(sqlite_extras::text),
+        json_error_position(sqlite_extras::blob),
         json_pretty(sqlite_extras::json),
         json_pretty(sqlite_extras::jsonb),
         json_pretty_with_indentation(sqlite_extras::json, "  "),