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Copy pathnested_vars.rs
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465 lines (439 loc) Β· 13.9 KB
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//! Nested `Variant` member walking shared by generated script glue.
//!
//! The compiler used to emit these three helpers verbatim into every generated
//! script even though none of them names a per-script type, so a project with N
//! scripts compiled ~N copies. Generated code calls them here instead.
use perro_ids::ScriptMemberID;
use perro_variant::Variant;
/// Find the member `var` inside `value`, matching on the dotted path hash.
///
/// `field_names` labels the lanes of an array-mode struct at this level;
/// deeper levels are object-keyed, so recursion passes an empty slice.
pub fn get_nested_by_hash(
prefix: &str,
value: Variant,
var: ScriptMemberID,
field_names: &[&str],
) -> Option<Variant> {
if !has_members(&value, field_names) {
return None;
}
get_nested(&mut member_path(prefix), value, var, field_names)
}
fn get_nested(
path: &mut String,
value: Variant,
var: ScriptMemberID,
field_names: &[&str],
) -> Option<Variant> {
match value {
Variant::Object(obj) => {
for (key, child) in obj {
let len = path.len();
push_member(path, key.as_ref());
let found = if ScriptMemberID::from_string(path) == var {
Some(child)
} else {
get_nested(path, child, var, &[])
};
path.truncate(len);
if let Some(found) = found {
return Some(found);
}
}
None
}
Variant::Array(items) => {
for (idx, child) in items.into_iter().enumerate() {
let Some(key) = field_names.get(idx) else {
continue;
};
let len = path.len();
push_member(path, key);
let found = if ScriptMemberID::from_string(path) == var {
Some(child)
} else {
get_nested(path, child, var, &[])
};
path.truncate(len);
if let Some(found) = found {
return Some(found);
}
}
None
}
_ => None,
}
}
/// Replace the member `var` inside `value` with `new_value`, taken on the
/// first hit. Returns whether anything was written.
pub fn set_nested_by_hash(
prefix: &str,
value: &mut Variant,
var: ScriptMemberID,
new_value: &mut Option<Variant>,
field_names: &[&str],
) -> bool {
if new_value.is_none() || !has_members(value, field_names) {
return false;
}
set_nested(&mut member_path(prefix), value, var, new_value, field_names)
}
fn set_nested(
path: &mut String,
value: &mut Variant,
var: ScriptMemberID,
new_value: &mut Option<Variant>,
field_names: &[&str],
) -> bool {
match value {
Variant::Object(obj) => {
for (key, child) in obj {
let len = path.len();
push_member(path, key.as_ref());
let changed = set_child(path, child, var, new_value);
path.truncate(len);
if changed {
return true;
}
}
false
}
Variant::Array(items) => {
for (idx, child) in items.iter_mut().enumerate() {
let Some(key) = field_names.get(idx) else {
continue;
};
let len = path.len();
push_member(path, key);
let changed = set_child(path, child, var, new_value);
path.truncate(len);
if changed {
return true;
}
}
false
}
_ => false,
}
}
fn set_child(
path: &mut String,
child: &mut Variant,
var: ScriptMemberID,
new_value: &mut Option<Variant>,
) -> bool {
if ScriptMemberID::from_string(path) == var {
let Some(new_value) = new_value.take() else {
return false;
};
*child = new_value;
true
} else {
set_nested(path, child, var, new_value, &[])
}
}
/// Merge every key of an incoming object into `target` by member path.
/// Returns whether any member changed.
pub fn apply_nested_object(
prefix: &str,
target: &mut Variant,
incoming: Variant,
field_names: &[&str],
) -> bool {
let Variant::Object(obj) = incoming else {
return false;
};
if obj.is_empty() || !has_members(target, field_names) {
return false;
}
let mut changed = false;
let mut path = None;
for (key, value) in obj {
// Scene/editor patches almost always name a direct member. Avoid a
// complete hash walk of the target for those common one-level writes.
// Keep the hashed fallback for dotted/ambiguous names.
let value = match set_direct_child(target, key.as_ref(), value, field_names) {
Ok(()) => {
changed = true;
continue;
}
Err(value) => value,
};
let path = path.get_or_insert_with(|| member_path(prefix));
push_member(path, key.as_ref());
let member = ScriptMemberID::from_string(path);
path.truncate(prefix.len());
let mut value = Some(value);
changed |= set_nested(path, target, member, &mut value, field_names);
}
changed
}
/// Replace an exact direct child without building or hashing its full path.
///
/// The fallback walker still handles dotted keys that name deeper members.
fn set_direct_child(
target: &mut Variant,
key: &str,
value: Variant,
field_names: &[&str],
) -> Result<(), Variant> {
// A dot can either belong to a literal key or separate a nested member.
// Preserve the walker ordering for that ambiguous legacy form.
if key.as_bytes().contains(&b'.') {
return Err(value);
}
match target {
Variant::Object(obj) => {
let Some(child) = obj.get_mut(key) else {
return Err(value);
};
*child = value;
Ok(())
}
Variant::Array(items) => {
let Some(index) = field_names.iter().position(|name| *name == key) else {
return Err(value);
};
let Some(child) = items.get_mut(index) else {
return Err(value);
};
*child = value;
Ok(())
}
_ => Err(value),
}
}
fn has_members(value: &Variant, field_names: &[&str]) -> bool {
match value {
Variant::Object(obj) => !obj.is_empty(),
Variant::Array(items) => !items.is_empty() && !field_names.is_empty(),
_ => false,
}
}
// One reusable buffer per traversal; sibling/deep paths share its capacity.
fn member_path(prefix: &str) -> String {
let mut path = String::with_capacity(prefix.len() + 32);
path.push_str(prefix);
path
}
fn push_member(path: &mut String, key: &str) {
if !path.is_empty() {
path.push('.');
}
path.push_str(key);
}
#[cfg(test)]
mod tests {
use super::*;
use std::collections::BTreeMap;
use std::sync::Arc;
fn object(entries: &[(&str, Variant)]) -> Variant {
let mut map = BTreeMap::<Arc<str>, Variant>::new();
for (key, value) in entries {
map.insert(Arc::from(*key), value.clone());
}
Variant::Object(map)
}
fn number(value: i64) -> Variant {
Variant::from(value)
}
#[test]
fn get_walks_object_and_array_levels() {
let root = object(&[("inner", Variant::Array(vec![number(1), number(2)]))]);
let found = get_nested_by_hash(
"actors",
root,
ScriptMemberID::from_string("actors.inner"),
&[],
);
assert!(matches!(found, Some(Variant::Array(_))));
let array_root = Variant::Array(vec![number(7), number(8)]);
let found = get_nested_by_hash(
"actors",
array_root,
ScriptMemberID::from_string("actors.second"),
&["first", "second"],
);
assert_eq!(found, Some(number(8)));
}
#[test]
fn set_and_apply_write_nested_members() {
let mut root = object(&[("count", number(1)), ("label", number(2))]);
let mut value = Some(number(9));
assert!(set_nested_by_hash(
"leaf",
&mut root,
ScriptMemberID::from_string("leaf.count"),
&mut value,
&[],
));
assert!(value.is_none());
let incoming = object(&[("label", number(5))]);
assert!(apply_nested_object("leaf", &mut root, incoming, &[]));
assert_eq!(
get_nested_by_hash("leaf", root, ScriptMemberID::from_string("leaf.label"), &[]),
Some(number(5))
);
}
#[test]
fn apply_direct_members_handles_object_and_array_roots() {
let mut object_root = object(&[
("first", number(1)),
("second", number(2)),
("nested", object(&[("value", number(3))])),
]);
assert!(apply_nested_object(
"root",
&mut object_root,
object(&[("first", number(9)), ("second", number(8))]),
&[],
));
assert_eq!(
get_nested_by_hash(
"root",
object_root.clone(),
ScriptMemberID::from_string("root.first"),
&[],
),
Some(number(9))
);
assert_eq!(
get_nested_by_hash(
"root",
object_root,
ScriptMemberID::from_string("root.second"),
&[],
),
Some(number(8))
);
let mut array_root = Variant::Array(vec![number(1), number(2)]);
assert!(apply_nested_object(
"root",
&mut array_root,
object(&[("first", number(7)), ("second", number(6))]),
&["first", "second"],
));
assert_eq!(
get_nested_by_hash(
"root",
array_root.clone(),
ScriptMemberID::from_string("root.first"),
&["first", "second"],
),
Some(number(7))
);
assert_eq!(
get_nested_by_hash(
"root",
array_root,
ScriptMemberID::from_string("root.second"),
&["first", "second"],
),
Some(number(6))
);
}
#[test]
fn apply_dotted_member_keeps_legacy_nested_walk_order() {
let mut root = object(&[("a", object(&[("b", number(1))])), ("a.b", number(2))]);
assert!(apply_nested_object(
"root",
&mut root,
object(&[("a.b", number(9))]),
&[],
));
let Variant::Object(root) = root else {
panic!("test setup must create object root");
};
assert_eq!(root.get("a.b"), Some(&number(2)));
let Some(Variant::Object(a)) = root.get("a") else {
panic!("test setup must create nested a object");
};
assert_eq!(a.get("b"), Some(&number(9)));
}
#[test]
fn missing_member_reports_no_change() {
let mut root = object(&[("count", number(1))]);
let mut value = Some(number(3));
assert!(!set_nested_by_hash(
"leaf",
&mut root,
ScriptMemberID::from_string("leaf.nope"),
&mut value,
&[],
));
assert!(value.is_some());
assert!(!apply_nested_object("leaf", &mut root, number(4), &[]));
}
#[test]
fn path_buffer_restores_siblings_and_preserves_unicode_and_dots() {
for prefix in ["", "root", "ζ Ή.branch"] {
let mut root = object(&[
("a", object(&[("deep", number(1))])),
("z.θ", object(&[("value", number(2))])),
]);
let path = if prefix.is_empty() {
"z.θ.value".to_string()
} else {
format!("{prefix}.z.θ.value")
};
let member = ScriptMemberID::from_string(&path);
assert_eq!(
get_nested_by_hash(prefix, root.clone(), member, &[]),
Some(number(2))
);
let mut replacement = Some(number(9));
assert!(set_nested_by_hash(
prefix,
&mut root,
member,
&mut replacement,
&[]
));
assert!(replacement.is_none());
assert_eq!(
get_nested_by_hash(prefix, root.clone(), member, &[]),
Some(number(9))
);
assert!(apply_nested_object(
prefix,
&mut root,
object(&[("z.θ.value", number(5))]),
&[]
));
assert_eq!(
get_nested_by_hash(prefix, root, member, &[]),
Some(number(5))
);
}
}
#[test]
fn array_path_buffer_restores_after_child_miss() {
let mut root = Variant::Array(vec![object(&[("x", number(1))]), number(2)]);
let names = &["first", "second"];
let member = ScriptMemberID::from_string("root.second");
assert_eq!(
get_nested_by_hash("root", root.clone(), member, names),
Some(number(2))
);
assert!(apply_nested_object(
"root",
&mut root,
object(&[("first.x", number(3)), ("second", number(4))]),
names
));
assert_eq!(
get_nested_by_hash("root", root.clone(), member, names),
Some(number(4))
);
assert_eq!(
get_nested_by_hash(
"root",
root,
ScriptMemberID::from_string("root.first.x"),
names
),
Some(number(3))
);
}
}