feat(s2n-quic-core): generate state reactions to events (#2221)

quic/s2n-quic-core/src/state.rs

@@ -105,6 +105,89 @@ macro_rules! __state_event__ {
             );
         )*
 
+        #[cfg(test)]
+        pub fn test_transitions() -> impl ::core::fmt::Debug {
+            use $crate::state::Error;
+            use ::core::{fmt, result::Result};
+
+            let mut all_states = [
+                // collect all of the states we've observed
+                $($(
+                    $(
+                        (stringify!($valid), Self::$valid),
+                    )*
+                    (stringify!($target), Self::$target),
+                )*)*
+            ];
+
+            all_states.sort_unstable_by_key(|v| v.0);
+            let (sorted, _) = $crate::slice::partition_dedup(&mut all_states);
+
+            const EVENT_LEN: usize = {
+                let mut len = 0;
+                $({
+                    let _ = stringify!($event);
+                    len += 1;
+                })*
+                len
+            };
+
+            let apply = |state: &Self| {
+                [$({
+                    let mut state = state.clone();
+                    let result = state.$event().map(|_| state);
+                    (stringify!($event), result)
+                }),*]
+            };
+
+            struct Transitions<const L: usize, T, A> {
+                states: [(&'static str, T); L],
+                count: usize,
+                apply: A,
+            }
+
+            impl<const L: usize, T, A> fmt::Debug for Transitions<L, T, A>
+            where
+                T: fmt::Debug,
+                A: Fn(&T) -> [(&'static str, Result<T, Error<T>>); EVENT_LEN],
+            {
+                fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                    let mut m = f.debug_map();
+
+                    for (name, state) in self.states.iter().take(self.count) {
+                        let events = (self.apply)(state);
+                        m.entry(&format_args!("{name}"), &Entry(events));
+                    }
+
+                    m.finish()
+                }
+            }
+
+            struct Entry<T>([(&'static str, Result<T, Error<T>>); EVENT_LEN]);
+
+            impl<T> fmt::Debug for Entry<T>
+            where
+                T: fmt::Debug
+            {
+                fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                    let mut m = f.debug_map();
+
+                    for (event, outcome) in self.0.iter() {
+                        m.entry(&format_args!("{event}"), outcome);
+                    }
+
+                    m.finish()
+                }
+            }
+
+            let count = sorted.len();
+            Transitions {
+                states: all_states,
+                count,
+                apply,
+            }
+        }
+
         /// Generates a dot graph of all state transitions
         pub fn dot() -> impl ::core::fmt::Display {
             struct Dot;

quic/s2n-quic-core/src/state/snapshots/s2n_quic_core__state__tests__snapshots.snap

@@ -1,128 +1,86 @@
 ---
 source: quic/s2n-quic-core/src/state/tests.rs
-expression: outcomes
+expression: "State::test_transitions()"
 ---
-[
-    (
-        Init,
-        "on_left",
-        Ok(
+{
+    Init: {
+        on_left: Ok(
             Left,
         ),
-    ),
-    (
-        Init,
-        "on_right",
-        Ok(
+        on_right: Ok(
             Right,
         ),
-    ),
-    (
-        Left,
-        "on_left",
-        Ok(
+    },
+    Left: {
+        on_left: Ok(
             LeftLeft,
         ),
-    ),
-    (
-        Left,
-        "on_right",
-        Ok(
+        on_right: Ok(
             LeftRight,
         ),
-    ),
-    (
-        Right,
-        "on_left",
-        Ok(
-            RightLeft,
-        ),
-    ),
-    (
-        Right,
-        "on_right",
-        Ok(
-            RightRight,
-        ),
-    ),
-    (
-        LeftLeft,
-        "on_left",
-        Err(
+    },
+    LeftLeft: {
+        on_left: Err(
             InvalidTransition {
                 current: LeftLeft,
                 event: "on_left",
             },
         ),
-    ),
-    (
-        LeftLeft,
-        "on_right",
-        Err(
+        on_right: Err(
             InvalidTransition {
                 current: LeftLeft,
                 event: "on_right",
             },
         ),
-    ),
-    (
-        LeftRight,
-        "on_left",
-        Err(
+    },
+    LeftRight: {
+        on_left: Err(
             InvalidTransition {
                 current: LeftRight,
                 event: "on_left",
             },
         ),
-    ),
-    (
-        LeftRight,
-        "on_right",
-        Err(
+        on_right: Err(
             InvalidTransition {
                 current: LeftRight,
                 event: "on_right",
             },
         ),
-    ),
-    (
-        RightLeft,
-        "on_left",
-        Err(
+    },
+    Right: {
+        on_left: Ok(
+            RightLeft,
+        ),
+        on_right: Ok(
+            RightRight,
+        ),
+    },
+    RightLeft: {
+        on_left: Err(
             InvalidTransition {
                 current: RightLeft,
                 event: "on_left",
             },
         ),
-    ),
-    (
-        RightLeft,
-        "on_right",
-        Err(
+        on_right: Err(
             InvalidTransition {
                 current: RightLeft,
                 event: "on_right",
             },
         ),
-    ),
-    (
-        RightRight,
-        "on_left",
-        Err(
+    },
+    RightRight: {
+        on_left: Err(
             InvalidTransition {
                 current: RightRight,
                 event: "on_left",
             },
         ),
-    ),
-    (
-        RightRight,
-        "on_right",
-        Err(
+        on_right: Err(
             InvalidTransition {
                 current: RightRight,
                 event: "on_right",
             },
         ),
-    ),
-]
+    },
+}

quic/s2n-quic-core/src/state/tests.rs

@@ -34,29 +34,7 @@ impl State {
 #[test]
 #[cfg_attr(miri, ignore)]
 fn snapshots() {
-    let mut outcomes = vec![];
-    let states = [
-        State::Init,
-        State::Left,
-        State::Right,
-        State::LeftLeft,
-        State::LeftRight,
-        State::RightLeft,
-        State::RightRight,
-    ];
-    for state in states {
-        macro_rules! push {
-            ($event:ident) => {
-                let mut target = state.clone();
-                let result = target.$event().map(|_| target);
-                outcomes.push((state.clone(), stringify!($event), result));
-            };
-        }
-        push!(on_left);
-        push!(on_right);
-    }
-
-    assert_debug_snapshot!(outcomes);
+    assert_debug_snapshot!(State::test_transitions());
 }
 
 #[test]

quic/s2n-quic-core/src/stream/state/recv.rs

@@ -74,31 +74,7 @@ mod tests {
     #[test]
     #[cfg_attr(miri, ignore)]
     fn snapshots() {
-        let mut outcomes = vec![];
-        let states = [
-            Receiver::Recv,
-            Receiver::SizeKnown,
-            Receiver::DataRecvd,
-            Receiver::DataRead,
-            Receiver::ResetRecvd,
-            Receiver::ResetRead,
-        ];
-        for state in states {
-            macro_rules! push {
-                ($event:ident) => {
-                    let mut target = state.clone();
-                    let result = target.$event().map(|_| target);
-                    outcomes.push((state.clone(), stringify!($event), result));
-                };
-            }
-            push!(on_receive_fin);
-            push!(on_receive_all_data);
-            push!(on_app_read_all_data);
-            push!(on_reset);
-            push!(on_app_read_reset);
-        }
-
-        assert_debug_snapshot!(outcomes);
+        assert_debug_snapshot!(Receiver::test_transitions());
     }
 
     #[test]

quic/s2n-quic-core/src/stream/state/send.rs

@@ -80,33 +80,7 @@ mod tests {
     #[test]
     #[cfg_attr(miri, ignore)]
     fn snapshots() {
-        let mut outcomes = vec![];
-        let states = [
-            Sender::Ready,
-            Sender::Send,
-            Sender::DataSent,
-            Sender::DataRecvd,
-            Sender::ResetQueued,
-            Sender::ResetSent,
-            Sender::ResetRecvd,
-        ];
-        for state in states {
-            macro_rules! push {
-                ($event:ident) => {
-                    let mut target = state.clone();
-                    let result = target.$event().map(|_| target);
-                    outcomes.push((state.clone(), stringify!($event), result));
-                };
-            }
-            push!(on_send_stream);
-            push!(on_send_fin);
-            push!(on_queue_reset);
-            push!(on_send_reset);
-            push!(on_recv_all_acks);
-            push!(on_recv_reset_ack);
-        }
-
-        assert_debug_snapshot!(outcomes);
+        assert_debug_snapshot!(Sender::test_transitions());
     }
 
     #[test]