anchors 0.6.0

async incremental computations
Documentation 
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use crate::expert::{AnchorExt, AnchorSplit};
#[test]
fn test_cutoff_simple_observed() {
    let mut engine = crate::singlethread::Engine::new();
    let (v, v_setter) = crate::expert::Var::new(100i32);
    let mut old_val = 0i32;
    let post_cutoff = v
        .cutoff(move |new_val| {
            if (old_val - *new_val).abs() < 50 {
                false
            } else {
                old_val = *new_val;
                true
            }
        })
        .map(|v| *v + 10);
    engine.mark_observed(&post_cutoff);
    assert_eq!(engine.get(&post_cutoff), 110);
    v_setter.set(125);
    assert_eq!(engine.get(&post_cutoff), 110);
    v_setter.set(151);
    assert_eq!(engine.get(&post_cutoff), 161);
    v_setter.set(125);
    assert_eq!(engine.get(&post_cutoff), 161);
}

#[test]
fn test_cutoff_simple_unobserved() {
    let mut engine = crate::singlethread::Engine::new();
    let (v, v_setter) = crate::expert::Var::new(100i32);
    let mut old_val = 0i32;
    let post_cutoff = v
        .cutoff(move |new_val| {
            if (old_val - *new_val).abs() < 50 {
                false
            } else {
                old_val = *new_val;
                true
            }
        })
        .map(|v| *v + 10);
    assert_eq!(engine.get(&post_cutoff), 110);
    v_setter.set(125);
    assert_eq!(engine.get(&post_cutoff), 110);
    v_setter.set(151);
    assert_eq!(engine.get(&post_cutoff), 161);
    v_setter.set(125);
    assert_eq!(engine.get(&post_cutoff), 161);
}

#[test]
fn test_refmap_simple() {
    #[derive(PartialEq, Debug)]
    struct NoClone(usize);

    let mut engine = crate::singlethread::Engine::new();
    let (v, _) = crate::expert::Var::new((NoClone(1), NoClone(2)));
    let a = v.refmap(|(a, _)| a);
    let b = v.refmap(|(_, b)| b);
    let a_correct = a.map(|a| a == &NoClone(1));
    let b_correct = b.map(|b| b == &NoClone(2));
    assert!(engine.get(&a_correct));
    assert!(engine.get(&b_correct));
}

#[test]
fn test_split_simple() {
    let mut engine = crate::singlethread::Engine::new();
    let (v, _) = crate::expert::Var::new((1usize, 2usize, 3usize));
    let (a, b, c) = v.split();
    assert_eq!(engine.get(&a), 1);
    assert_eq!(engine.get(&b), 2);
    assert_eq!(engine.get(&c), 3);
}

#[test]
fn test_map_simple() {
    let mut engine = crate::singlethread::Engine::new();
    let (v1, _v1_setter) = crate::expert::Var::new(1usize);
    let (v2, _v2_setter) = crate::expert::Var::new(123usize);
    let _a2 = v1.map(|num1| {
        println!("a: adding to {:?}", num1);
        *num1
    });
    let a = AnchorExt::map((&v1, &v2), |num1, num2| num1 + num2);

    let b = AnchorExt::map((&v1, &a, &v2), |num1, num2, num3| num1 + num2 + num3);
    engine.mark_observed(&b);
    engine.stabilize();
    assert_eq!(engine.get(&b), 248);
}

#[test]
fn test_then_simple() {
    let mut engine = crate::singlethread::Engine::new();
    let (v1, v1_setter) = crate::expert::Var::new(true);
    let (v2, _v2_setter) = crate::expert::Var::new(10usize);
    let (v3, _v3_setter) = crate::expert::Var::new(20usize);
    let a = v1.then(move |val| if *val { v2.clone() } else { v3.clone() });
    engine.mark_observed(&a);
    engine.stabilize();
    assert_eq!(engine.get(&a), 10);

    v1_setter.set(false);
    engine.stabilize();
    assert_eq!(engine.get(&a), 20);
}

#[test]
fn test_observed_marking() {
    use crate::singlethread::ObservedState;

    let mut engine = crate::singlethread::Engine::new();
    let (v1, _v1_setter) = crate::expert::Var::new(1usize);
    let a = v1.map(|num1| *num1 + 1);
    let b = a.map(|num1| *num1 + 2);
    let c = b.map(|num1| *num1 + 3);
    engine.mark_observed(&a);
    engine.mark_observed(&c);

    assert_eq!(ObservedState::Unnecessary, engine.check_observed(&v1));
    assert_eq!(ObservedState::Observed, engine.check_observed(&a));
    assert_eq!(ObservedState::Unnecessary, engine.check_observed(&b));
    assert_eq!(ObservedState::Observed, engine.check_observed(&c));

    engine.stabilize();

    assert_eq!(ObservedState::Necessary, engine.check_observed(&v1));
    assert_eq!(ObservedState::Observed, engine.check_observed(&a));
    assert_eq!(ObservedState::Necessary, engine.check_observed(&b));
    assert_eq!(ObservedState::Observed, engine.check_observed(&c));

    engine.mark_unobserved(&c);

    assert_eq!(ObservedState::Necessary, engine.check_observed(&v1));
    assert_eq!(ObservedState::Observed, engine.check_observed(&a));
    assert_eq!(ObservedState::Unnecessary, engine.check_observed(&b));
    assert_eq!(ObservedState::Unnecessary, engine.check_observed(&c));

    engine.mark_unobserved(&a);

    assert_eq!(ObservedState::Unnecessary, engine.check_observed(&v1));
    assert_eq!(ObservedState::Unnecessary, engine.check_observed(&a));
    assert_eq!(ObservedState::Unnecessary, engine.check_observed(&b));
    assert_eq!(ObservedState::Unnecessary, engine.check_observed(&c));
}

#[test]
fn test_garbage_collection_wont_panic() {
    let mut engine = crate::singlethread::Engine::new();
    let (v1, _v1_setter) = crate::expert::Var::new(1usize);
    engine.get(&v1);
    std::mem::drop(v1);
    engine.stabilize();
}

#[test]
fn test_readme_example() {
    // example
    use crate::{expert::AnchorExt, expert::Var, singlethread::Engine};
    let mut engine = Engine::new();

    // create a couple `Var`s
    let (my_name, my_name_updater) = Var::new("Bob".to_string());
    let (my_unread, my_unread_updater) = Var::new(999usize);

    // `my_name` is a `Var`, our first type of `Anchor`. we can pull an `Anchor`'s value out with our `engine`:
    assert_eq!(&engine.get(&my_name), "Bob");
    assert_eq!(engine.get(&my_unread), 999);

    // we can create a new `Anchor` from another one using `map`. The function won't actually run until absolutely necessary.
    // also feel free to clone an `Anchor` — the clones will all refer to the same inner state
    let my_greeting = my_name.clone().map(|name| {
        println!("calculating name!");
        format!("Hello, {}!", name)
    });
    assert_eq!(engine.get(&my_greeting), "Hello, Bob!"); // prints "calculating name!"

    // we can update a `Var` with its updater. values are cached unless one of its dependencies changes
    assert_eq!(engine.get(&my_greeting), "Hello, Bob!"); // doesn't print anything
    my_name_updater.set("Robo".to_string());
    assert_eq!(engine.get(&my_greeting), "Hello, Robo!"); // prints "calculating name!"

    // a `map` can take values from multiple `Anchor`s. just use tuples:
    let header = (&my_greeting, &my_unread)
        .map(|greeting, unread| format!("{} You have {} new messages.", greeting, unread));
    assert_eq!(
        engine.get(&header),
        "Hello, Robo! You have 999 new messages."
    );

    // just like a future, you can dynamically decide which `Anchor` to use with `then`:
    let (insulting_name, _) = Var::new("Lazybum".to_string());
    let dynamic_name = my_unread.then(move |unread| {
        // only use the user's real name if the have less than 100 messages in their inbox
        if *unread < 100 {
            my_name.clone()
        } else {
            insulting_name.clone()
        }
    });
    assert_eq!(engine.get(&dynamic_name), "Lazybum");
    my_unread_updater.set(50);
    assert_eq!(engine.get(&dynamic_name), "Robo");
}