Allow duration literals without date component (#394)

## Usage and product changes

We modify the grammar to accept a `duration_literal` without a date
component (e.g. `PT1S`) as per the standard.

## Implementation

The valid duration literals are:

- `"P" ~ duration_weeks` 
- `"P" ~ duration_date`
- `"P" ~ duration_date ~ "T" ~ duration_time`
- `"PT" ~ duration_time`

The last option was missing from the grammar.

Author: dmitrii-ubskii

rust/parser/literal.rs

@@ -167,6 +167,10 @@ fn visit_duration_literal(node: Node<'_>) -> DurationLiteral {
             let time = children.try_consume_expected(Rule::duration_time).map(visit_duration_time);
             DurationLiteral::DateAndTime(date, time)
         }
+        Rule::duration_time => {
+            let time = visit_duration_time(child);
+            DurationLiteral::Time(time)
+        }
         _ => unreachable!("{}", TypeQLError::IllegalGrammar { input: child.to_string() }),
     };
     debug_assert_eq!(children.try_consume_any(), None);

rust/parser/typeql.pest

@@ -557,7 +557,7 @@ date_literal = ${ date_fragment ~ WB }
 datetime_literal = ${ date_fragment ~ "T" ~ time ~ WB }
 datetime_tz_literal = ${ date_fragment ~ "T" ~ time ~ ( " " ~ iana_timezone | iso8601_timezone_offset ) ~ WB }
 
-duration_literal = ${ "P" ~ ( duration_weeks | duration_date ~ ( "T" ~ duration_time )? ) ~ WB}
+duration_literal = ${ "P" ~ ( duration_weeks | duration_date ~ ( "T" ~ duration_time )? | "T" ~ duration_time ) ~ WB}
 
 quoted_string_literal = @{ "\"" ~ ( !"\"" ~ !"\\" ~ ANY | escape_seq )* ~ "\""
                          | "'" ~ ( !"'" ~ !"\\" ~ ANY | escape_seq )* ~ "'" }

rust/value.rs

@@ -99,6 +99,7 @@ pub enum TimeZone {
 pub enum DurationLiteral {
     Weeks(IntegerLiteral),
     DateAndTime(DurationDate, Option<DurationTime>),
+    Time(DurationTime),
 }
 
 #[derive(Debug, Clone, Eq, PartialEq)]
@@ -328,6 +329,7 @@ impl fmt::Display for DurationLiteral {
                     Some(time) => write!(f, "T{time}")?,
                 }
             }
+            DurationLiteral::Time(time) => write!(f, "T{time}")?,
         }
         Ok(())
     }