Add a module that helps handle a list of record changes. #1
6
Makefile
6
Makefile
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@ -1,4 +1,10 @@
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changeset-dev:
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cd changeset && make dev
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changeset-test:
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cd changeset && make test
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emseries-dev:
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cd emseries && make dev
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@ -0,0 +1,48 @@
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# This file is automatically @generated by Cargo.
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# It is not intended for manual editing.
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version = 3
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[[package]]
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name = "cfg-if"
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version = "1.0.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
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[[package]]
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name = "changeset"
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version = "0.1.0"
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dependencies = [
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"uuid",
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]
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[[package]]
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name = "getrandom"
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version = "0.2.8"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "c05aeb6a22b8f62540c194aac980f2115af067bfe15a0734d7277a768d396b31"
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dependencies = [
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"cfg-if",
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"libc",
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"wasi",
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]
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[[package]]
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name = "libc"
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version = "0.2.139"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "201de327520df007757c1f0adce6e827fe8562fbc28bfd9c15571c66ca1f5f79"
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[[package]]
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name = "uuid"
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version = "1.2.2"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "422ee0de9031b5b948b97a8fc04e3aa35230001a722ddd27943e0be31564ce4c"
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dependencies = [
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"getrandom",
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]
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[[package]]
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name = "wasi"
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version = "0.11.0+wasi-snapshot-preview1"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
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@ -0,0 +1,11 @@
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[package]
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name = "changeset"
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version = "0.1.0"
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edition = "2021"
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# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
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[dependencies]
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[dev-dependencies]
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uuid = { version = "*", features = [ "v4" ] }
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@ -0,0 +1,9 @@
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dev:
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cargo watch -x build
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test:
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cargo watch -x test
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test-once:
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cargo test
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@ -0,0 +1,192 @@
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use std::{
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collections::{HashMap, HashSet},
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hash::Hash,
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};
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pub trait Constructable {
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fn new() -> Self;
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}
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#[derive(Clone, Debug, PartialEq)]
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pub enum Change<Key: Eq + Hash, Value> {
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DeleteRecord(Key),
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UpdateRecord((Key, Value)),
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NewRecord(Value),
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}
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#[derive(Clone, Debug)]
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pub struct Changeset<Key: Clone + Eq + Hash, Value> {
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delete: HashSet<Key>,
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update: HashMap<Key, Value>,
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new: HashMap<Key, Value>,
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}
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impl<Key: Clone + Constructable + Eq + Hash, Value> Changeset<Key, Value> {
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pub fn new() -> Self {
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Self {
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delete: HashSet::new(),
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update: HashMap::new(),
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new: HashMap::new(),
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}
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}
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pub fn add(&mut self, r: Value) -> Key {
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let k = Key::new();
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self.new.insert(k.clone(), r);
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k.clone()
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}
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pub fn update(&mut self, k: Key, v: Value) {
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match self.new.get_mut(&k) {
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Some(record) => *record = v,
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None => {
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let _ = self.update.insert(k, v);
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}
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}
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}
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pub fn delete(&mut self, k: Key) {
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let new_v = self.new.remove(&k);
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let updated_v = self.update.remove(&k);
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match (new_v.is_some(), updated_v.is_some()) {
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(false, false) => {
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let _ = self.delete.insert(k);
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}
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(true, false) => (),
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(false, true) => {
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let _ = self.delete.insert(k);
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}
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(true, true) => {
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panic!("state error: key exists in the new and updtade columns at once")
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}
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}
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}
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}
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impl<Key: Clone + Eq + Hash, Value> From<Changeset<Key, Value>> for Vec<Change<Key, Value>> {
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fn from(changes: Changeset<Key, Value>) -> Self {
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let Changeset {
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delete,
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update,
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new,
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} = changes;
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delete
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.into_iter()
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.map(|k| Change::DeleteRecord(k))
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.chain(
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update
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.into_iter()
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.map(|(k, v)| Change::UpdateRecord((k, v))),
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)
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.chain(new.into_iter().map(|(_, v)| Change::NewRecord(v)))
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.collect()
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use uuid::Uuid;
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#[derive(Clone, PartialEq, Eq, Hash)]
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struct Id(Uuid);
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impl Constructable for Id {
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fn new() -> Self {
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Id(Uuid::new_v4())
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}
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}
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#[test]
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fn it_generates_a_new_record() {
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let mut set: Changeset<Id, String> = Changeset::new();
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set.add("efgh".to_string());
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let changes = Vec::from(set.clone());
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assert_eq!(changes.len(), 1);
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assert!(changes.contains(&Change::NewRecord("efgh".to_string())));
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set.add("wxyz".to_string());
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let changes = Vec::from(set);
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assert_eq!(changes.len(), 2);
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assert!(changes.contains(&Change::NewRecord("efgh".to_string())));
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assert!(changes.contains(&Change::NewRecord("wxyz".to_string())));
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}
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#[test]
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fn it_generates_a_delete_record() {
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let mut set: Changeset<Id, String> = Changeset::new();
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let id1 = Id::new();
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set.delete(id1.clone());
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let changes = Vec::from(set.clone());
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assert_eq!(changes.len(), 1);
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assert!(changes.contains(&Change::DeleteRecord(id1.clone())));
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let id2 = Id::new();
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set.delete(id2.clone());
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let changes = Vec::from(set);
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assert_eq!(changes.len(), 2);
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assert!(changes.contains(&Change::DeleteRecord(id1)));
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assert!(changes.contains(&Change::DeleteRecord(id2)));
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}
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#[test]
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fn update_unrelated_records() {
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let mut set: Changeset<Id, String> = Changeset::new();
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let id1 = Id::new();
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let id2 = Id::new();
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set.update(id1.clone(), "abcd".to_owned());
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set.update(id2.clone(), "efgh".to_owned());
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let changes = Vec::from(set);
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assert_eq!(changes.len(), 2);
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assert!(changes.contains(&Change::UpdateRecord((id1, "abcd".to_owned()))));
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assert!(changes.contains(&Change::UpdateRecord((id2, "efgh".to_owned()))));
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}
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#[test]
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fn delete_cancels_new() {
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let mut set: Changeset<Id, String> = Changeset::new();
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let key = set.add("efgh".to_string());
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set.delete(key);
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let changes = Vec::from(set);
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assert_eq!(changes.len(), 0);
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}
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#[test]
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fn delete_cancels_update() {
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let mut set: Changeset<Id, String> = Changeset::new();
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let id = Id::new();
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set.update(id.clone(), "efgh".to_owned());
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set.delete(id.clone());
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let changes = Vec::from(set);
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assert_eq!(changes.len(), 1);
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assert!(changes.contains(&Change::DeleteRecord(id)));
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}
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#[test]
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fn update_atop_new_is_new() {
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let mut set: Changeset<Id, String> = Changeset::new();
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let key = set.add("efgh".to_owned());
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set.update(key, "wxyz".to_owned());
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let changes = Vec::from(set);
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assert_eq!(changes.len(), 1);
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assert!(changes.contains(&Change::NewRecord("wxyz".to_string())));
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}
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#[test]
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fn updates_get_squashed() {
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let mut set: Changeset<Id, String> = Changeset::new();
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let id1 = Id::new();
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let id2 = Id::new();
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set.update(id1.clone(), "efgh".to_owned());
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set.update(id2.clone(), "efgh".to_owned());
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let changes = Vec::from(set.clone());
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assert_eq!(changes.len(), 2);
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assert!(changes.contains(&Change::UpdateRecord((id1.clone(), "efgh".to_string()))));
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assert!(changes.contains(&Change::UpdateRecord((id2.clone(), "efgh".to_string()))));
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set.update(id1.clone(), "wxyz".to_owned());
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let changes = Vec::from(set);
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assert_eq!(changes.len(), 2);
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assert!(changes.contains(&Change::UpdateRecord((id1, "wxyz".to_string()))));
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assert!(changes.contains(&Change::UpdateRecord((id2, "efgh".to_string()))));
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}
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}
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