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fix(expr): keep the live memory footprint accurate when errors are absorbed #417

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Merged
mwiebe merged 1 commit into from
Sep 29, 2026
Merged

fix(expr): keep the live memory footprint accurate when errors are absorbed #417

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188 changes: 136 additions & 52 deletions crates/openjd-expr/src/eval/evaluator.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,17 @@ fn contains_budget_error(err: &ExpressionError) -> bool {
) || err.sub_errors().iter().any(contains_budget_error)
}

/// Outcome of evaluating a sub-expression whose failure an enclosing
/// construct may absorb (see [`Evaluator::eval_speculative`]).
enum Speculative {
/// Evaluated to a value; it is tracked.
Value(ExprValue),
/// Failed with a value error that the caller absorbs. The
/// evaluator's live footprint has been reset to what it was before
/// the attempt; the spend (peak memory, operation count) stands.
Absorbed(ExpressionError),
}

/// Default memory limit: 100 million bytes.
pub const DEFAULT_MEMORY_LIMIT: usize = 100_000_000; // 100 million bytes per spec

Expand Down Expand Up @@ -464,24 +475,43 @@ impl<'a> Evaluator<'a> {
self.current_memory = self.current_memory.saturating_sub(size);
}

fn dispatch_with_node(
/// Call a library function. The arguments are consumed by the call,
/// so they are released from the live footprint whether the call
/// succeeds or fails; a successful result is tracked. Releasing on
/// failure matters when an enclosing construct absorbs the error and
/// keeps evaluating (see `eval_speculative`): the operands are gone
/// and must not stay charged. `eval_call` releases its arguments
/// before dispatch for the same reason.
///
/// The operation-count check before the call is the one exit that
/// does not release. It fails only with a budget error, which is
/// never absorbed, so the footprint is not read afterwards.
fn dispatch_released(
&mut self,
name: &str,
args: Vec<ExprValue>,
node: Option<&ast::Expr>,
) -> Result<ExprValue, ExpressionError> {
self.count_op()?;
let input_size: usize = args.iter().map(|a| a.memory_size()).sum();
let lib = self.library;
let result = lib.call(name, &args, self).map_err(|e| {
let result = lib.call(name, &args, self);
self.current_memory = self.current_memory.saturating_sub(input_size);
self.track(result?)
}

fn dispatch_with_node(
&mut self,
name: &str,
args: Vec<ExprValue>,
node: Option<&ast::Expr>,
) -> Result<ExprValue, ExpressionError> {
self.dispatch_released(name, args).map_err(|e| {
if let (Some(src), Some(n)) = (self.expr_source, node) {
e.with_node(src, n)
} else {
e
}
})?;
self.current_memory = self.current_memory.saturating_sub(input_size);
self.track(result)
})
}

/// Like `dispatch_with_node` but uses a `TextRange` for error positioning,
Expand All @@ -492,18 +522,13 @@ impl<'a> Evaluator<'a> {
args: Vec<ExprValue>,
range: ruff_text_size::TextRange,
) -> Result<ExprValue, ExpressionError> {
self.count_op()?;
let input_size: usize = args.iter().map(|a| a.memory_size()).sum();
let lib = self.library;
let result = lib.call(name, &args, self).map_err(|e| {
self.dispatch_released(name, args).map_err(|e| {
if let Some(src) = self.expr_source {
e.with_span(src, range.start().to_usize(), range.end().to_usize())
} else {
e
}
})?;
self.current_memory = self.current_memory.saturating_sub(input_size);
self.track(result)
})
}

fn eval_number(&mut self, n: &ast::ExprNumberLiteral) -> Result<ExprValue, ExpressionError> {
Expand Down Expand Up @@ -759,34 +784,31 @@ impl<'a> Evaluator<'a> {
ast::BoolOp::Or => false,
});
let mut seen_unresolved = false;
for node in &b.values {
let last_index = b.values.len().saturating_sub(1);
for (index, node) in b.values.iter().enumerate() {
let is_last = index == last_index;
if seen_unresolved {
// After an unresolved operand, suppress errors in subsequent operands
// (the unresolved value might short-circuit at runtime).
// But if a subsequent operand determines the result, return it.
match self.eval_node(node, None) {
Ok(val) => match b.op {
// After an unresolved operand, later operands are still
// evaluated to catch type errors, but a value error is
// absorbed: the unresolved operand might short-circuit
// at runtime. A concrete operand that decides the result
// is still returned.
match self.eval_speculative(node, None)? {
Speculative::Value(val) => match b.op {
ast::BoolOp::And => {
if matches!(&val, ExprValue::Null | ExprValue::Bool(false)) {
return Ok(val);
}
self.release(&val);
}
ast::BoolOp::Or => {
if !matches!(&val, ExprValue::Null | ExprValue::Bool(false)) {
return Ok(val);
}
self.release(&val);
}
},
Err(e) => {
// Suppressed — unresolved might short-circuit.
// Except budget exceedances: the memory and
// operations were spent in this evaluation no
// matter what a runtime short-circuit skips
// (same rule as `eval_ifexp`).
if contains_budget_error(&e) {
return Err(e);
}
}
Speculative::Absorbed(_) => {}
}
continue;
}
Expand All @@ -798,6 +820,9 @@ impl<'a> Evaluator<'a> {
// `int` target must not try to coerce the `true`).
last = self.eval_node(node, None)?;
if last.is_unresolved() {
// The result will be a fresh `Unresolved(BOOL)`, so this
// placeholder is not kept.
self.release(&last);
seen_unresolved = true;
continue;
}
Expand All @@ -814,6 +839,12 @@ impl<'a> Evaluator<'a> {
}
}
}
// This operand did not decide the result and is replaced by
// the next one. The final operand is returned, so it stays
// tracked.
if !is_last {
self.release(&last);
}
}
if seen_unresolved {
return self.track(ExprValue::unresolved(ExprType::BOOL));
Expand All @@ -838,16 +869,24 @@ impl<'a> Evaluator<'a> {
// or `Param.Path < 1`) is refused at validation time rather than on
// the worker. Only the value is deferred, not the type check.
let mut seen_unresolved = false;
for (op, right_node) in c.ops.iter().zip(c.comparators.iter()) {
let last_index = c.ops.len().saturating_sub(1);
for (index, (op, right_node)) in c.ops.iter().zip(c.comparators.iter()).enumerate() {
let right = self.eval_node(right_node, None)?;
let dispatch = table.cmpop(*op)?;
let op_name = dispatch.dunder;

// Dispatch consumes and releases both operands. When the
// chain continues, `right` is also the next link's `left`,
// so it is cloned first and the clone is tracked below as
// the value the chain carries. Each operand is therefore
// charged once and released by the link that consumes it.
let is_last = index == last_index;
let carried = if is_last { None } else { Some(right.clone()) };
// For 'in'/'not in', container is first arg (right), item is second (left)
let args = if dispatch.container_first {
vec![right.clone(), left.clone()]
vec![right, left]
} else {
vec![left.clone(), right.clone()]
vec![left, right]
};

// Use the compare expression's range for error caret positioning
Expand All @@ -865,14 +904,14 @@ impl<'a> Evaluator<'a> {
};
self.release(&result_val);
if !result {
self.release(&left);
self.release(&right);
return self.track(ExprValue::Bool(false));
}
self.release(&left);
left = right;
match carried {
// The carried operand stays live for the next link.
Some(next_left) => left = self.track(next_left)?,
None => break,
}
}
self.release(&left);
if seen_unresolved {
return self.track(ExprValue::unresolved(ExprType::BOOL));
}
Expand Down Expand Up @@ -910,11 +949,15 @@ impl<'a> Evaluator<'a> {
});
}
self.release(&test);
// Try both branches, catching errors (e.g. fail() in one branch)
let body = self.eval_node(&i.body, target);
let orelse = self.eval_node(&i.orelse, target);
// Evaluate both branches speculatively. A budget error in
// either propagates immediately. A value error is absorbed,
// because a runtime with the test resolved may never take
// that branch. The result is an `Unresolved` carrying only a
// type, so every branch value is released.
let body = self.eval_speculative(&i.body, target)?;
let orelse = self.eval_speculative(&i.orelse, target)?;
match (body, orelse) {
(Err(be), Err(oe)) => {
(Speculative::Absorbed(be), Speculative::Absorbed(oe)) => {
let mut msg = format!(
"Both branches fail in the if/else:\n if-branch: {}\n",
be.message()
Expand All @@ -931,25 +974,21 @@ impl<'a> Evaluator<'a> {
}
Err(err)
}
(Ok(b), Err(oe)) => {
if contains_budget_error(&oe) {
self.release(&b);
return Err(oe);
}
(Speculative::Value(b), Speculative::Absorbed(_)) => {
let t = unwrap_unresolved(&b.expr_type());
self.release(&b);
self.track(ExprValue::unresolved(t))
}
(Err(be), Ok(o)) => {
if contains_budget_error(&be) {
self.release(&o);
return Err(be);
}
(Speculative::Absorbed(_), Speculative::Value(o)) => {
let t = unwrap_unresolved(&o.expr_type());
self.release(&o);
self.track(ExprValue::unresolved(t))
}
(Ok(b), Ok(o)) => {
(Speculative::Value(b), Speculative::Value(o)) => {
let bt = unwrap_unresolved(&b.expr_type());
let ot = unwrap_unresolved(&o.expr_type());
self.release(&b);
self.release(&o);
if bt == ot {
self.track(ExprValue::unresolved(bt))
} else {
Expand Down Expand Up @@ -1203,6 +1242,19 @@ impl<'a> Evaluator<'a> {
}
}
}
// The elements were tracked as they were evaluated. From here
// they are consumed into the list, which is charged as one value
// (or as a type-only placeholder when any element is
// unresolved), so release them first. Otherwise the literal would
// be charged for the list and for every element again, both in
// the construction pre-check and for as long as the list is
// held. The error returns above leave the elements charged like
// any failed sub-expression's operands; an enclosing construct
// that absorbs the error resets the footprint (see
// `eval_speculative`).
for e in &elements {
self.release(e);
}
if elements.iter().any(|e| e.is_unresolved()) {
let val = unresolved_list_from_elements(&elements)?;
return self.track(val);
Expand Down Expand Up @@ -1425,6 +1477,38 @@ impl<'a> Evaluator<'a> {
self.current_memory = baseline;
}

/// Evaluate `node` where the caller may absorb a failure: the
/// branches of an unresolved-test conditional, or the operands of a
/// boolop after an unresolved one. Both absorption rules live here so
/// that every absorbing construct applies both:
///
/// - A budget error (`MemoryLimitExceeded` / `OperationLimitExceeded`,
/// directly or inside a compound error's sub-errors) is returned as
/// `Err`. The memory and operations were spent regardless of what
/// a runtime would skip.
/// - A value error is returned as `Absorbed`, and the live footprint
/// is reset to what it was before the attempt. The failed
/// sub-expression's values are gone. Peak memory and the operation
/// count keep what the attempt consumed.
///
/// The caller decides what an absorbed failure means: an `Unresolved`
/// result, a short-circuit, or a compound error.
fn eval_speculative(
&mut self,
node: &ast::Expr,
target: Option<&crate::types::ExprType>,
) -> Result<Speculative, ExpressionError> {
let baseline = self.current_memory;
match self.eval_node(node, target) {
Ok(v) => Ok(Speculative::Value(v)),
Err(e) if contains_budget_error(&e) => Err(e),
Err(e) => {
self.current_memory = baseline;
Ok(Speculative::Absorbed(e))
}
}
}

/// Conclude a list comprehension whose result cannot be computed at
/// this stage — because the iterable is unresolved, or because the
/// filter evaluated to an unresolved condition on a concrete
Expand Down
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