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//! Testing-only StateMgr that stores values in a hash table.
use crate::err::{Action, ErrorSource, Resource};
use crate::{Error, LockStatus, Result, StateMgr};
use serde::{de::DeserializeOwned, Serialize};
use std::collections::HashMap;
use std::sync::{Arc, Mutex};
/// A state manager for testing support, that allows simulating persistence
/// without having to store anything to disk.
///
/// Only available when this crate is built with the `testing` feature.
#[cfg_attr(docsrs, doc(cfg(feature = "testing")))]
#[derive(Clone, Debug)]
pub struct TestingStateMgr {
/// Inner reference-counted storage.
inner: Arc<Mutex<TestingStateMgrInner>>,
}
/// The inner state of a TestingStateMgr.
#[derive(Debug)]
struct TestingStateMgrInner {
/// True if this manager, and all references to it, hold the lock on
/// the storage.
lock_held: bool,
/// The underlying shared storage object.
storage: Arc<Mutex<TestingStateMgrStorage>>,
impl TestingStateMgrInner {
/// Release the lock, if we hold it. Otherwise, do nothing.
fn unlock(&mut self) {
if self.lock_held {
self.lock_held = false;
let mut storage = self.storage.lock().expect("Lock poisoned");
storage.lock_available = true;
/// Implementation type for [`TestingStateMgr`]: represents an underlying
/// storage system that can be shared by multiple TestingStateMgr instances
/// at a time, only one of which can hold the lock.
struct TestingStateMgrStorage {
/// True if nobody currently holds the lock for this storage.
lock_available: bool,
/// Map from key to JSON-encoded values.
/// We serialize our values here for convenience (so that we don't
/// have to use `Any`) and to try to detect any
/// serialization-related bugs.
entries: HashMap<String, String>,
impl Default for TestingStateMgr {
fn default() -> Self {
Self::new()
impl TestingStateMgr {
/// Create a new empty unlocked [`TestingStateMgr`].
pub fn new() -> Self {
let storage = TestingStateMgrStorage {
lock_available: true,
entries: HashMap::new(),
};
let inner = TestingStateMgrInner {
lock_held: false,
storage: Arc::new(Mutex::new(storage)),
TestingStateMgr {
inner: Arc::new(Mutex::new(inner)),
/// Create a new unlocked [`TestingStateMgr`] that shares the same
/// underlying storage with this one.
#[must_use]
pub fn new_manager(&self) -> Self {
let inner = self.inner.lock().expect("Lock poisoned.");
let new_inner = TestingStateMgrInner {
storage: Arc::clone(&inner.storage),
inner: Arc::new(Mutex::new(new_inner)),
/// Return an error Resource corresponding to a given `key`.
fn err_resource(&self, key: &str) -> Resource {
Resource::Temporary {
key: key.to_string(),
impl StateMgr for TestingStateMgr {
fn load<D>(&self, key: &str) -> Result<Option<D>>
where
D: DeserializeOwned,
{
let storage = inner.storage.lock().expect("Lock poisoned.");
let content = storage.entries.get(key);
match content {
Some(value) => {
Ok(Some(serde_json::from_str(value).map_err(|e| {
Error::new(e, Action::Loading, self.err_resource(key))
})?))
None => Ok(None),
fn store<S>(&self, key: &str, val: &S) -> Result<()>
S: Serialize,
if !inner.lock_held {
return Err(Error::new(
ErrorSource::NoLock,
Action::Storing,
Resource::Manager,
));
let mut storage = inner.storage.lock().expect("Lock poisoned.");
let val = serde_json::to_string_pretty(val)
.map_err(|e| Error::new(e, Action::Storing, self.err_resource(key)))?;
storage.entries.insert(key.to_string(), val);
Ok(())
fn can_store(&self) -> bool {
inner.lock_held
fn try_lock(&self) -> Result<LockStatus> {
let mut inner = self.inner.lock().expect("Lock poisoned.");
if inner.lock_held {
return Ok(LockStatus::AlreadyHeld);
let mut storage = inner.storage.lock().expect("Lock poisoned");
if storage.lock_available {
storage.lock_available = false;
drop(storage); // release borrow
inner.lock_held = true;
Ok(LockStatus::NewlyAcquired)
} else {
Ok(LockStatus::NoLock)
fn unlock(&self) -> Result<()> {
inner.unlock();
impl Drop for TestingStateMgrInner {
fn drop(&mut self) {
self.unlock();
#[cfg(test)]
mod test {
// @@ begin test lint list maintained by maint/add_warning @@
#![allow(clippy::bool_assert_comparison)]
#![allow(clippy::clone_on_copy)]
#![allow(clippy::dbg_macro)]
#![allow(clippy::mixed_attributes_style)]
#![allow(clippy::print_stderr)]
#![allow(clippy::print_stdout)]
#![allow(clippy::single_char_pattern)]
#![allow(clippy::unwrap_used)]
#![allow(clippy::unchecked_duration_subtraction)]
#![allow(clippy::useless_vec)]
#![allow(clippy::needless_pass_by_value)]
//! <!-- @@ end test lint list maintained by maint/add_warning @@ -->
use super::*;
use serde::{Deserialize, Serialize};
#[derive(Eq, PartialEq, Clone, Debug, Serialize, Deserialize)]
struct Ex1 {
v1: u32,
v2: u64,
struct Ex2 {
s1: String,
s2: String,
enum OldEnum {
Variant1,
enum NewEnum {
Variant2,
#[test]
fn basic_tests() {
let mgr = TestingStateMgr::new();
let v1 = Ex1 { v1: 8, v2: 99 };
let s1 = Ex2 {
s1: "Hello".into(),
s2: "World".into(),
assert_eq!(mgr.load::<Ex1>("item1").unwrap(), None);
assert!(matches!(
mgr.store("item1", &v1).unwrap_err().source(),
ErrorSource::NoLock
assert!(!mgr.can_store());
assert_eq!(mgr.try_lock().unwrap(), LockStatus::NewlyAcquired);
assert!(mgr.can_store());
assert!(mgr.store("item1", &v1).is_ok());
assert_eq!(mgr.load::<Ex1>("item1").unwrap(), Some(v1));
assert!(mgr.load::<Ex2>("item1").is_err());
assert!(mgr.store("item2", &s1).is_ok());
assert_eq!(mgr.load::<Ex2>("item2").unwrap(), Some(s1));
assert!(mgr.load::<Ex1>("item2").is_err());
let v2 = Ex1 { v1: 10, v2: 12 };
assert!(mgr.store("item1", &v2).is_ok());
assert_eq!(mgr.load::<Ex1>("item1").unwrap(), Some(v2));
fn lock_blocking() {
let mgr2 = mgr.new_manager();
assert_eq!(mgr.try_lock().unwrap(), LockStatus::AlreadyHeld);
assert!(!mgr2.can_store());
assert_eq!(mgr2.try_lock().unwrap(), LockStatus::NoLock);
drop(mgr);
assert_eq!(mgr2.try_lock().unwrap(), LockStatus::NewlyAcquired);
assert!(mgr2.can_store());
fn typesafe_handles() {
use crate::DynStorageHandle;
let h1: DynStorageHandle<Ex1> = mgr.clone().create_handle("foo");
let h2: DynStorageHandle<Ex2> = mgr.clone().create_handle("bar");
let h3: DynStorageHandle<Ex2> = mgr.clone().create_handle("baz");
let v1 = Ex1 { v1: 1, v2: 2 };
s1: "aaa".into(),
s2: "bbb".into(),
let s2 = Ex2 {
s1: "jj".into(),
s2: "yrfmstbyes".into(),
h1.store(&v1).unwrap_err().source(),
assert!(mgr.try_lock().unwrap().held());
assert!(h1.can_store());
assert!(h1.store(&v1).is_ok());
assert!(h2.can_store());
assert!(h2.store(&s1).is_ok());
assert!(h3.load().unwrap().is_none());
assert!(h3.store(&s2).is_ok());
assert_eq!(h1.load().unwrap(), Some(v1));
assert_eq!(h2.load().unwrap(), Some(s1));
assert_eq!(h3.load().unwrap(), Some(s2));
fn futureproof() {
use crate::Futureproof;
let v1_ser = serde_json::to_string(&v1).unwrap();
let v1_as_ex1: Futureproof<Ex1> = serde_json::from_str(&v1_ser).unwrap();
let v1_as_ex2: Futureproof<Ex2> = serde_json::from_str(&v1_ser).unwrap();
assert!(v1_as_ex1.clone().into_option().is_some());
assert!(v1_as_ex2.into_option().is_none());
assert_eq!(serde_json::to_string(&v1_as_ex1).unwrap(), v1_ser);
fn futureproof_enums() {
let new1 = NewEnum::Variant1;
let new2 = NewEnum::Variant2;
let new1_ser = serde_json::to_string(&new1).unwrap();
let new2_ser = serde_json::to_string(&new2).unwrap();
let old1: Futureproof<OldEnum> = serde_json::from_str(&new1_ser).unwrap();
let old2: Futureproof<OldEnum> = serde_json::from_str(&new2_ser).unwrap();
assert!(old1.into_option().is_some());
assert!(old2.into_option().is_none());