Add support for postgre jsonb_set_lax

[accestfromim]

#4216
Though create_if_missing and null_value_treatment is optional, the case without them is already supported in jsonb_set and jsonb_set_create_if_missing. So I just do not treat them as optional field here. Do you think it's ok?

[weiznich]

Thanks for opening this PR. The definition looks ok, but I would like to make the invariant for the null_value_treatment parameter a bit more robust by only accepting enum values with any of the allowed values there. I've left more detailed instructions for this a comment on the code itself. If you need help implementing that please let me know.

[weiznich]

I would rather prefer having an enum with all allowed variants instead of allowing a text input here.

That would require something like this:

diesel/diesel/src/pg/types/mod.rs

Lines 211 to 232 in 9861bcb

	/// This is a wrapper for [`RangeBound`] to represent range bounds: '[]', '(]', '[)', '()',
	/// used in functions int4range, int8range, numrange, tsrange, tstzrange, daterange.
	#[derive(Debug, Clone, Copy, QueryId, SqlType)]
	#[cfg(feature = "postgres_backend")]
	#[diesel(postgres_type(name = "text"))]
	pub struct RangeBoundEnum;
	/// Represent postgres range bounds: '[]', '(]', '[)', '()',
	/// used in functions int4range, int8range, numrange, tsrange, tstzrange, daterange.
	#[derive(Debug, Clone, Copy, diesel_derives::AsExpression)]
	#[diesel(sql_type = RangeBoundEnum)]
	#[allow(clippy::enum_variant_names)]
	pub enum RangeBound {
	/// postgres '[]'
	LowerBoundInclusiveUpperBoundInclusive,
	/// postgres '[)'
	LowerBoundInclusiveUpperBoundExclusive,
	/// postgres '(]'
	LowerBoundExclusiveUpperBoundInclusive,
	/// postgres '()'
	LowerBoundExclusiveUpperBoundExclusive,
	}

and

diesel/diesel/src/pg/types/ranges.rs

Lines 276 to 289 in 9861bcb

	#[cfg(feature = "postgres_backend")]
	impl ToSql<RangeBoundEnum, Pg> for RangeBound {
	fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Pg>) -> serialize::Result {
	let literal = match self {
	Self::LowerBoundInclusiveUpperBoundInclusive => "[]",
	Self::LowerBoundInclusiveUpperBoundExclusive => "[)",
	Self::LowerBoundExclusiveUpperBoundInclusive => "(]",
	Self::LowerBoundExclusiveUpperBoundExclusive => "()",
	};
	out.write_all(literal.as_bytes())
	.map(|_| IsNull::No)
	.map_err(|e| Box::new(e) as Box<dyn Error + Send + Sync>)
	}
	}

with the corresponding enum variants.

Afterwards the function signature needs to change so that it accepts only the SQL type (RangeBoundEnum in that example) instead of arbitrary text. (See here for an example usage:

diesel/diesel/src/pg/expression/functions.rs

Line 442 in 9861bcb

fn int4range(lower: Nullable<Integer>, upper: Nullable<Integer>, bound: RangeBoundEnum) -> Int4range;

)

[accestfromim]

Thank you for your kind instructions.
I impl to_sql in a new mod called json_function_enum, do you think it's ok?
I'm ready to make more changes if you think it's not fit to make a new mod for it.

[weiznich]

No it's good that way, thanks for implementing this change ❤️

[weiznich]

Looks good now, thanks for the fast update 👍