diesel/expression_methods/

bool_expression_methods.rs

use crate::dsl;
use crate::expression::grouped::Grouped;
use crate::expression::operators::{And, Or};
use crate::expression::{AsExpression, Expression, TypedExpressionType};
use crate::sql_types::{self, BoolOrNullableBool, SqlType};

/// Methods present on boolean expressions
pub trait BoolExpressionMethods: Expression + Sized {
    /// Creates a SQL `AND` expression
    ///
    /// # Example
    ///
    /// ```
    /// # include!("../doctest_setup.rs");
    /// #
    /// # // Reading the query result requires reading memory allocated by the
    /// # // native sqlite library, which miri cannot track provenance for.
    /// # #[cfg(miri)]
    /// # fn main() {}
    /// # #[cfg(not(miri))]
    /// # fn main() {
    /// #     run_test().unwrap();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use schema::animals::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// #
    /// diesel::insert_into(animals)
    ///     .values(&vec![
    ///         (species.eq("ferret"), legs.eq(4), name.eq("Freddy")),
    ///         (species.eq("ferret"), legs.eq(4), name.eq("Jack")),
    ///     ])
    ///     .execute(connection)?;
    ///
    /// let data = animals
    ///     .select((species, name))
    ///     .filter(species.eq("ferret").and(name.eq("Jack")))
    ///     .load(connection)?;
    /// let expected = vec![(String::from("ferret"), Some(String::from("Jack")))];
    /// assert_eq!(expected, data);
    /// #     Ok(())
    /// # }
    /// ```
    fn and<T, ST>(self, other: T) -> dsl::And<Self, T, ST>
    where
        Self::SqlType: SqlType,
        ST: SqlType + TypedExpressionType + BoolOrNullableBool,
        T: AsExpression<ST>,
        And<Self, T::Expression>: Expression,
    {
        Grouped(And::new(self, other.as_expression()))
    }

    /// Creates a SQL `OR` expression
    ///
    /// The result will be wrapped in parenthesis, so that precedence matches
    /// that of your function calls. For example, `false.and(false.or(true))`
    /// will generate the SQL `FALSE AND (FALSE OR TRUE)`, which returns `false`
    ///
    /// # Example
    ///
    /// ```
    /// # include!("../doctest_setup.rs");
    /// #
    /// # // Reading the query result requires reading memory allocated by the
    /// # // native sqlite library, which miri cannot track provenance for.
    /// # #[cfg(miri)]
    /// # fn main() {}
    /// # #[cfg(not(miri))]
    /// # fn main() {
    /// #     run_test().unwrap();
    /// # }
    /// #
    /// # fn run_test() -> QueryResult<()> {
    /// #     use schema::animals::dsl::*;
    /// #     let connection = &mut establish_connection();
    /// #
    /// diesel::insert_into(animals)
    ///     .values(&vec![
    ///         (species.eq("ferret"), legs.eq(4), name.eq("Freddy")),
    ///         (species.eq("ferret"), legs.eq(4), name.eq("Jack")),
    ///     ])
    ///     .execute(connection)?;
    ///
    /// let data = animals
    ///     .select((species, name))
    ///     .filter(species.eq("ferret").or(name.eq("Jack")))
    ///     .load(connection)?;
    /// let expected = vec![
    ///     (String::from("dog"), Some(String::from("Jack"))),
    ///     (String::from("ferret"), Some(String::from("Freddy"))),
    ///     (String::from("ferret"), Some(String::from("Jack"))),
    /// ];
    /// assert_eq!(expected, data);
    /// #     Ok(())
    /// # }
    /// ```
    fn or<T, ST>(self, other: T) -> dsl::Or<Self, T, ST>
    where
        Self::SqlType: SqlType,
        ST: SqlType + TypedExpressionType + BoolOrNullableBool,
        T: AsExpression<ST>,
        Or<Self, T::Expression>: Expression,
    {
        Grouped(Or::new(self, other.as_expression()))
    }
}

impl<T> BoolExpressionMethods for T
where
    T: Expression,
    T::SqlType: BoolOrNullableBool,
{
}

/// Allow ~type inference on [And](crate::helper_types::And) and [Or](crate::helper_types::Or)
/// helper types
///
/// This is used to be statistically correct as last generic parameter of `dsl::And` and `dsl::Or`
/// without having to specify an additional type parameter.
///
/// It works with types that are [Expression]s and have a [`SqlType`](Expression::SqlType) that is
/// either [`Bool`](sql_types::Bool) or [`Nullable<Bool>`](sql_types::Nullable), and with [`bool`]
/// (and `Option<bool>` and references to those).
///
/// Cases where an additional type parameter would still have to be specified in the helper type
/// generic parameters are:
/// - If this trait isn't implemented for the `other` parameter of the expression
///   (in that case the user (you?) probably wants to implement it)
/// - If the user actually was using the not-preferred implementation of `AsExpression`
///   (e.g. towards `Nullable<Bool>` instead of `Bool`)
pub trait PreferredBoolSqlType {
    /// The preferred `Bool` SQL type for this AsExpression implementation.
    ///
    /// That should be either `Bool` or `Nullable<Bool>`.
    type PreferredSqlType;
}

impl<E: Expression> PreferredBoolSqlType for E
where
    E::SqlType: BoolOrNullableBool,
{
    type PreferredSqlType = <E as Expression>::SqlType;
}

/// This impl has to live in Diesel because otherwise it would conflict with the blanket impl above
/// because "diesel might add an implementation of Expression for bool"
impl PreferredBoolSqlType for bool {
    type PreferredSqlType = sql_types::Bool;
}

impl PreferredBoolSqlType for &bool {
    type PreferredSqlType = sql_types::Bool;
}

impl PreferredBoolSqlType for &&bool {
    type PreferredSqlType = sql_types::Bool;
}

impl PreferredBoolSqlType for Option<bool> {
    type PreferredSqlType = sql_types::Nullable<sql_types::Bool>;
}

impl PreferredBoolSqlType for &Option<bool> {
    type PreferredSqlType = sql_types::Nullable<sql_types::Bool>;
}

impl PreferredBoolSqlType for &&Option<bool> {
    type PreferredSqlType = sql_types::Nullable<sql_types::Bool>;
}