proptest/strategy/
filter.rsuse crate::std_facade::{fmt, Arc};
use crate::strategy::traits::*;
use crate::test_runner::*;
#[must_use = "strategies do nothing unless used"]
pub struct Filter<S, F> {
pub(super) source: S,
pub(super) whence: Reason,
pub(super) fun: Arc<F>,
}
impl<S, F> Filter<S, F> {
pub(super) fn new(source: S, whence: Reason, fun: F) -> Self {
Self {
source,
whence,
fun: Arc::new(fun),
}
}
}
impl<S: fmt::Debug, F> fmt::Debug for Filter<S, F> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("Filter")
.field("source", &self.source)
.field("whence", &self.whence)
.field("fun", &"<function>")
.finish()
}
}
impl<S: Clone, F> Clone for Filter<S, F> {
fn clone(&self) -> Self {
Filter {
source: self.source.clone(),
whence: "unused".into(),
fun: Arc::clone(&self.fun),
}
}
}
impl<S: Strategy, F: Fn(&S::Value) -> bool> Strategy for Filter<S, F> {
type Tree = Filter<S::Tree, F>;
type Value = S::Value;
fn new_tree(&self, runner: &mut TestRunner) -> NewTree<Self> {
loop {
let val = self.source.new_tree(runner)?;
if !(self.fun)(&val.current()) {
runner.reject_local(self.whence.clone())?;
} else {
return Ok(Filter {
source: val,
whence: self.whence.clone(),
fun: Arc::clone(&self.fun),
});
}
}
}
}
impl<S: ValueTree, F: Fn(&S::Value) -> bool> Filter<S, F> {
fn ensure_acceptable(&mut self) {
while !(self.fun)(&self.source.current()) {
if !self.source.complicate() {
panic!(
"Unable to complicate filtered strategy \
back into acceptable value"
);
}
}
}
}
impl<S: ValueTree, F: Fn(&S::Value) -> bool> ValueTree for Filter<S, F> {
type Value = S::Value;
fn current(&self) -> S::Value {
self.source.current()
}
fn simplify(&mut self) -> bool {
if self.source.simplify() {
self.ensure_acceptable();
true
} else {
false
}
}
fn complicate(&mut self) -> bool {
if self.source.complicate() {
self.ensure_acceptable();
true
} else {
false
}
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_filter() {
let input = (0..256).prop_filter("%3", |&v| 0 == v % 3);
for _ in 0..256 {
let mut runner = TestRunner::default();
let mut case = input.new_tree(&mut runner).unwrap();
assert!(0 == case.current() % 3);
while case.simplify() {
assert!(0 == case.current() % 3);
}
assert!(0 == case.current() % 3);
}
}
#[test]
fn test_filter_sanity() {
check_strategy_sanity(
(0..256).prop_filter("!%5", |&v| 0 != v % 5),
Some(CheckStrategySanityOptions {
strict_complicate_after_simplify: false,
..CheckStrategySanityOptions::default()
}),
);
}
}