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Changed Lookahead to support multiple fields #574

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merged 2 commits into from
Jul 15, 2021
Merged

Changed Lookahead to support multiple fields #574

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a868a9a
Changed Lookahead to support multiple fields
oeed Jul 15, 2021
4e685f6
Update CHANGELOG.md
oeed Jul 15, 2021
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
## [Unreleased]

- Add binary types to `ConstValue` and `Value`. [#569](https://github.com/async-graphql/async-graphql/issues/569)
- Changed Lookahead to support multiple fields. [#574](https://github.com/async-graphql/async-graphql/issues/547)

## [2.9.8] 2021-07-12

Expand Down
120 changes: 95 additions & 25 deletions src/look_ahead.rs
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Expand Up @@ -6,7 +6,7 @@ use crate::{Name, Positioned, SelectionField};
/// A selection performed by a query.
pub struct Lookahead<'a> {
fragments: &'a HashMap<Name, Positioned<FragmentDefinition>>,
field: Option<&'a Field>,
fields: Vec<&'a Field>,
}

impl<'a> Lookahead<'a> {
Expand All @@ -16,63 +16,68 @@ impl<'a> Lookahead<'a> {
) -> Self {
Self {
fragments,
field: Some(field),
fields: vec![field],
}
}

/// Get the first subfield of the selection set with the specified name. This will ignore
/// Get the field of the selection set with the specified name. This will ignore
/// aliases.
///
/// For example, calling `.field("a")` on `{ a { b } }` will return a lookahead that
/// represents `{ b }`.
pub fn field(&self, name: &str) -> Self {
let mut fields = Vec::new();
for field in &self.fields {
filter(&mut fields, self.fragments, &field.selection_set.node, name)
}

Self {
fragments: self.fragments,
field: self
.field
.and_then(|field| find(self.fragments, &field.selection_set.node, name)),
fields,
}
}

/// Returns true if field exists otherwise return false.
#[inline]
pub fn exists(&self) -> bool {
self.field.is_some()
!self.fields.is_empty()
}
}

impl<'a> From<SelectionField<'a>> for Lookahead<'a> {
fn from(selection_field: SelectionField<'a>) -> Self {
Lookahead {
fragments: selection_field.fragments,
field: Some(selection_field.field),
fields: vec![selection_field.field],
}
}
}

fn find<'a>(
fn filter<'a>(
fields: &mut Vec<&'a Field>,
fragments: &'a HashMap<Name, Positioned<FragmentDefinition>>,
selection_set: &'a SelectionSet,
name: &str,
) -> Option<&'a Field> {
selection_set
.items
.iter()
.find_map(|item| match &item.node {
) {
for item in &selection_set.items {
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I've done this imperatively. Tried doing this with iterators but I'm pretty sure you need to use a Box<dyn Iterator> because it's recursive. Happy to change if there's a better way though.

// doing this imperatively is a bit nasty, but using iterators would
// require a boxed return type (I believe) as its recusive
match &item.node {
Selection::Field(field) => {
if field.node.name.node == name {
Some(&field.node)
} else {
None
fields.push(&field.node)
}
}
Selection::InlineFragment(fragment) => {
find(fragments, &fragment.node.selection_set.node, name)
filter(fields, fragments, &fragment.node.selection_set.node, name)
}
Selection::FragmentSpread(spread) => {
if let Some(fragment) = fragments.get(&spread.node.fragment_name.node) {
filter(fields, fragments, &fragment.node.selection_set.node, name)
}
}
Selection::FragmentSpread(spread) => fragments
.get(&spread.node.fragment_name.node)
.and_then(|fragment| find(fragments, &fragment.node.selection_set.node, name)),
})
}
}
}

#[cfg(test)]
Expand Down Expand Up @@ -104,12 +109,17 @@ mod tests {
if ctx.look_ahead().field("a").exists() {
// This is a query like `obj { a }`
assert_eq!(n, 1);
} else if ctx.look_ahead().field("detail").field("c").exists() {
} else if ctx.look_ahead().field("detail").field("c").exists()
&& ctx.look_ahead().field("detail").field("d").exists()
{
// This is a query like `obj { detail { c } }`
assert_eq!(n, 2);
} else if ctx.look_ahead().field("detail").field("c").exists() {
// This is a query like `obj { detail { c } }`
assert_eq!(n, 3);
} else {
// This query doesn't have `a`
assert_eq!(n, 3);
assert_eq!(n, 4);
}
MyObj {
a: 0,
Expand Down Expand Up @@ -143,10 +153,27 @@ mod tests {
.await
.is_ok());

assert!(schema
.execute(
r#"{
obj(n: 3) {
detail {
c
}
}
}"#,
)
.await
.is_ok());

assert!(schema
.execute(
r#"{
obj(n: 2) {
detail {
d
}

detail {
c
}
Expand All @@ -159,7 +186,7 @@ mod tests {
assert!(schema
.execute(
r#"{
obj(n: 3) {
obj(n: 4) {
b
}
}"#,
Expand All @@ -180,11 +207,30 @@ mod tests {
.await
.is_ok());

assert!(schema
.execute(
r#"{
obj(n: 3) {
... {
detail {
c
}
}
}
}"#,
)
.await
.is_ok());

assert!(schema
.execute(
r#"{
obj(n: 2) {
... {
detail {
d
}

detail {
c
}
Expand All @@ -210,15 +256,39 @@ mod tests {
.await
.is_ok());

assert!(schema
.execute(
r#"{
obj(n: 3) {
... A
}
}

fragment A on MyObj {
detail {
c
}
}"#,
)
.await
.is_ok());

assert!(schema
.execute(
r#"{
obj(n: 2) {
... A
... B
}
}

fragment A on MyObj {
detail {
d
}
}

fragment B on MyObj {
detail {
c
}
Expand Down