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fix default slice start in parser #559

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merged 1 commit into from
Oct 26, 2024
Merged

fix default slice start in parser #559

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44 changes: 42 additions & 2 deletions crates/rsonpath-syntax/src/builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -417,6 +417,8 @@ impl From<JsonPathQueryBuilder> for JsonPathQuery {
/// ```
pub struct SliceBuilder {
inner: Slice,
/// We need to track if start is explicit because the default depends on step sign.
start_was_explicitly_given: bool,
}

impl SliceBuilder {
Expand All @@ -432,13 +434,15 @@ impl SliceBuilder {
pub fn new() -> Self {
Self {
inner: Slice::default(),
start_was_explicitly_given: false,
}
}

/// Set the start of the [`Slice`].
#[inline]
pub fn with_start<N: Into<JsonInt>>(&mut self, start: N) -> &mut Self {
self.inner.start = start.into().into();
self.start_was_explicitly_given = true;
self
}

Expand All @@ -462,15 +466,23 @@ impl SliceBuilder {
#[inline]
#[must_use]
pub fn to_slice(&mut self) -> Slice {
if !self.start_was_explicitly_given {
if self.inner.step.is_forward() {
self.inner.start = Slice::DEFAULT_START_FORWARDS;
} else {
self.inner.start = Slice::default_start_backwards();
}
}

self.inner.clone()
}
}

impl From<SliceBuilder> for Slice {
#[inline]
#[must_use]
fn from(value: SliceBuilder) -> Self {
value.inner
fn from(mut value: SliceBuilder) -> Self {
value.to_slice()
}
}

Expand Down Expand Up @@ -805,3 +817,31 @@ impl From<LogicalExprBuilder> for LogicalExpr {
value.current
}
}

#[cfg(test)]
mod tests {
use super::SliceBuilder;
use crate::{Index, Slice, Step};

#[test]
fn slice_builder_default_start_forward() {
let mut builder = SliceBuilder::new();
builder.with_end(3).with_step(4);
let slice: Slice = builder.into();

assert_eq!(slice.start(), Index::FromStart(0.into()));
assert_eq!(slice.end(), Some(Index::FromStart(3.into())));
assert_eq!(slice.step(), Step::Forward(4.into()));
}

#[test]
fn slice_builder_default_start_backward() {
let mut builder = SliceBuilder::new();
builder.with_end(3).with_step(-4);
let slice: Slice = builder.into();

assert_eq!(slice.start(), Index::FromEnd(1.try_into().unwrap()));
assert_eq!(slice.end(), Some(Index::FromStart(3.into())));
assert_eq!(slice.step(), Step::Backward(4.try_into().unwrap()));
}
}
13 changes: 10 additions & 3 deletions crates/rsonpath-syntax/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -542,8 +542,13 @@ pub struct Slice {
}

impl Slice {
const DEFAULT_START: Index = Index::FromStart(num::JsonUInt::ZERO);
const DEFAULT_STEP: Step = Step::Forward(num::JsonUInt::ONE);
pub(crate) const DEFAULT_START_FORWARDS: Index = Index::FromStart(num::JsonUInt::ZERO);
/// This is not const because the required NonZeroU64::MIN is from Rust 1.70.
#[inline(always)]
pub(crate) fn default_start_backwards() -> Index {
Index::FromEnd(1.try_into().expect("const 1 is nonzero"))
}
pub(crate) const DEFAULT_STEP: Step = Step::Forward(num::JsonUInt::ONE);

/// Create a new [`Slice`] from given bounds and step.
#[inline(always)]
Expand Down Expand Up @@ -1180,7 +1185,9 @@ impl Display for Step {
impl Display for Slice {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if self.start != Self::DEFAULT_START {
if (self.step.is_forward() && self.start != Self::DEFAULT_START_FORWARDS)
|| (self.step.is_backward() && self.start != Self::default_start_backwards())
{
write!(f, "{}", self.start)?;
}
write!(f, ":")?;
Expand Down
16 changes: 12 additions & 4 deletions crates/rsonpath-syntax/src/parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -336,6 +336,11 @@ fn slice_selector(q: &str) -> IResult<&str, Selector, InternalParseError> {
};
}

// Fixup the bounds - if start was not given and step is negative, the default must be reversed.
if slice.step.is_backward() && opt_start.is_none() {
slice.start = crate::Slice::default_start_backwards();
}

Ok((rest, Selector::Slice(slice)))
}

Expand Down Expand Up @@ -1020,8 +1025,8 @@ mod tests {
#[test_case("-3:-4:-5", Index::FromEnd(3.try_into().unwrap()), Some(Index::FromEnd(4.try_into().unwrap())), Step::Backward(5.try_into().unwrap()); "test m3cm4cm5")]
#[test_case(":4:5", Index::FromStart(0.into()), Some(Index::FromStart(4.into())), Step::Forward(5.into()); "test c4c5")]
#[test_case(":-4:5", Index::FromStart(0.into()), Some(Index::FromEnd(4.try_into().unwrap())), Step::Forward(5.into()); "test cm4c5")]
#[test_case(":4:-5", Index::FromStart(0.into()), Some(Index::FromStart(4.into())), Step::Backward(5.try_into().unwrap()); "test c4cm5")]
#[test_case(":-4:-5", Index::FromStart(0.into()), Some(Index::FromEnd(4.try_into().unwrap())), Step::Backward(5.try_into().unwrap()); "test cm4cm5")]
#[test_case(":4:-5", Index::FromEnd(1.try_into().unwrap()), Some(Index::FromStart(4.into())), Step::Backward(5.try_into().unwrap()); "test c4cm5")]
#[test_case(":-4:-5", Index::FromEnd(1.try_into().unwrap()), Some(Index::FromEnd(4.try_into().unwrap())), Step::Backward(5.try_into().unwrap()); "test cm4cm5")]
#[test_case("3::5", Index::FromStart(3.into()), None, Step::Forward(5.into()); "test 3cc5")]
#[test_case("-3::5", Index::FromEnd(3.try_into().unwrap()), None, Step::Forward(5.into()); "test m3cc5")]
#[test_case("3::-5", Index::FromStart(3.into()), None, Step::Backward(5.try_into().unwrap()); "test 3ccm5")]
Expand All @@ -1039,9 +1044,12 @@ mod tests {
#[test_case(":4", Index::FromStart(0.into()), Some(Index::FromStart(4.into())), Step::Forward(1.into()); "test c4")]
#[test_case(":-4", Index::FromStart(0.into()), Some(Index::FromEnd(4.try_into().unwrap())), Step::Forward(1.into()); "test cm4")]
#[test_case("::5", Index::FromStart(0.into()), None, Step::Forward(5.into()); "test cc5")]
#[test_case("::-5", Index::FromStart(0.into()), None, Step::Backward(5.try_into().unwrap()); "test ccm5")]
#[test_case("::-5", Index::FromEnd(1.try_into().unwrap()), None, Step::Backward(5.try_into().unwrap()); "test ccm5")]
#[test_case("::", Index::FromStart(0.into()), None, Step::Forward(1.into()); "test cc")]
fn full_positive_slice(input: &str, exp_start: Index, exp_end: Option<Index>, exp_step: Step) {
#[test_case("::-1", Index::FromEnd(1.try_into().unwrap()), None, Step::Backward(1.try_into().unwrap()); "test ccm1")]
#[test_case("0::-1", Index::FromStart(0.into()), None, Step::Backward(1.try_into().unwrap()); "test 0ccm1")]
#[test_case("0:0:-1", Index::FromStart(0.into()), Some(Index::FromStart(0.into())), Step::Backward(1.try_into().unwrap()); "test 0c0cm1")]
fn slice(input: &str, exp_start: Index, exp_end: Option<Index>, exp_step: Step) {
let (rest, selector) = super::slice_selector(input).expect("should parse");
assert_eq!("", rest);
match selector {
Expand Down
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