Change the IS NULL filter syntax to use the IS keyword

filter-parser/src/condition.rs

@@ -45,18 +45,19 @@ pub fn parse_condition(input: Span) -> IResult<FilterCondition> {
     Ok((input, condition))
 }
 
-/// null          = value "NULL"
-pub fn parse_null(input: Span) -> IResult<FilterCondition> {
-    let (input, key) = terminated(parse_value, tag("NULL"))(input)?;
+/// null          = value "IS" WS+ "NULL"
+pub fn parse_is_null(input: Span) -> IResult<FilterCondition> {
+    let (input, key) = parse_value(input)?;
 
+    let (input, _) = tuple((tag("IS"), multispace1, tag("NULL")))(input)?;
     Ok((input, FilterCondition::Condition { fid: key, op: Null }))
 }
 
-/// null          = value "NOT" WS+ "NULL"
-pub fn parse_not_null(input: Span) -> IResult<FilterCondition> {
+/// null          = value "IS" WS+ "NOT" WS+ "NULL"
+pub fn parse_is_not_null(input: Span) -> IResult<FilterCondition> {
     let (input, key) = parse_value(input)?;
 
-    let (input, _) = tuple((tag("NOT"), multispace1, tag("NULL")))(input)?;
+    let (input, _) = tuple((tag("IS"), multispace1, tag("NOT"), multispace1, tag("NULL")))(input)?;
     Ok((input, FilterCondition::Not(Box::new(FilterCondition::Condition { fid: key, op: Null }))))
 }
 

filter-parser/src/lib.rs

@@ -47,7 +47,7 @@ mod value;
 use std::fmt::Debug;
 
 pub use condition::{parse_condition, parse_to, Condition};
-use condition::{parse_exists, parse_not_exists, parse_not_null, parse_null};
+use condition::{parse_exists, parse_is_not_null, parse_is_null, parse_not_exists};
 use error::{cut_with_err, ExpectedValueKind, NomErrorExt};
 pub use error::{Error, ErrorKind};
 use nom::branch::alt;
@@ -414,8 +414,8 @@ fn parse_primary(input: Span, depth: usize) -> IResult<FilterCondition> {
         parse_in,
         parse_not_in,
         parse_condition,
-        parse_null,
-        parse_not_null,
+        parse_is_null,
+        parse_is_not_null,
         parse_exists,
         parse_not_exists,
         parse_to,
@@ -811,7 +811,7 @@ impl<'a> std::fmt::Display for Condition<'a> {
             Condition::GreaterThanOrEqual(token) => write!(f, ">= {token}"),
             Condition::Equal(token) => write!(f, "= {token}"),
             Condition::NotEqual(token) => write!(f, "!= {token}"),
-            Condition::Null => write!(f, "NULL"),
+            Condition::Null => write!(f, "IS NULL"),
             Condition::Exists => write!(f, "EXISTS"),
             Condition::LowerThan(token) => write!(f, "< {token}"),
             Condition::LowerThanOrEqual(token) => write!(f, "<= {token}"),

filter-parser/src/value.rs

@@ -180,7 +180,16 @@ fn is_syntax_component(c: char) -> bool {
 fn is_keyword(s: &str) -> bool {
     matches!(
         s,
-        "AND" | "OR" | "IN" | "NOT" | "TO" | "EXISTS" | "NULL" | "_geoRadius" | "_geoBoundingBox"
+        "AND"
+            | "OR"
+            | "IN"
+            | "NOT"
+            | "TO"
+            | "EXISTS"
+            | "IS"
+            | "NULL"
+            | "_geoRadius"
+            | "_geoBoundingBox"
     )
 }