filter-expr

A library for parsing the filter expression.

use filter_expr::{FilterExpr, SimpleContext};

let f = FilterExpr::parse("name = 'John' AND age > 18").unwrap();
let ctx = SimpleContext::new(HashMap::from([
    ("name".to_string(), "John".into()),
    ("age".to_string(), 19.into()),
]));
let result = f.eval(&ctx).await.unwrap();
assert_eq!(result, true);

Syntax

Filter

<filter> = <expression> | <empty>

<empty> =

Expression

<expression> = <sequence> ('AND' <sequence>)*

<sequence> = <factor>+
<factor> = <term> ('OR' <term>)*
<term> = ['NOT' | '-'] <simple>
<simple> = <restriction> | <composite>

Restriction

<restriction> = <comparable> [<operator> <arg>]

E.g. name = 'John' or age > 18 or 1 > 0.

Composite

<composite> = '(' <expression> ')'

E.g. (age + 18).

Comparable

<comparable> = <member> | <function> | <value>

E.g. name or age or 1.

Operator

<operator> = '=' | '>' | '<' | '>=' | '<=' | '!=' | 'IN' | 'NOT' 'IN'

Arg

<arg> = <comparable> | <composite>

E.g. 'John' or 18 or 1.0 or (age + 18).

Member

<member> = <field> ('.' <field>)*

E.g. name or user.name or user.address.city.

Field

E.g. name or user_name or user_address_city.

Value

<value> = <string>
        | <integer>
        | <float>
        | <boolean>
        | <null>
        | <array>
        | <object>

<string> = <single-quoted-string> | <double-quoted-string>
<boolean> = 'true' | 'false'
<integer> = /* an integer number */
<float> = /* a floating-point number */
<null> = 'null'
<array> = '[' [<value> (',' <value>)* ','?] ']'
<object> = '{' [<string> ':' <value> (',' <string> ':' <value>)* ','?] '}'

Examples:

• 'John'
• 18
• 1.0
• true
• false
• null
• [1, 2, 3]
• {'a': 1, 'b': 2}