From 72daa3f510ea381b7e3606c75f03ce6000dc780c Mon Sep 17 00:00:00 2001
From: Owen Jacobson <owen@grimoire.ca>
Date: Fri, 13 Sep 2024 02:22:57 -0400
Subject: Tolerate panics in channel::app where they can only be triggered by
 implementation errors.

---
 src/channel/app.rs | 49 +++++++++++++++++--------------------------------
 1 file changed, 17 insertions(+), 32 deletions(-)

(limited to 'src/channel/app.rs')

diff --git a/src/channel/app.rs b/src/channel/app.rs
index adefa3e..c060b23 100644
--- a/src/channel/app.rs
+++ b/src/channel/app.rs
@@ -16,7 +16,7 @@ use super::repo::{
 use crate::{
     clock::DateTime,
     error::BoxedError,
-    login::repo::logins::{Id as LoginId, Login, Provider as _},
+    login::repo::logins::{Login, Provider as _},
 };
 
 pub struct Channels<'a> {
@@ -32,9 +32,9 @@ impl<'a> Channels<'a> {
     pub async fn create(&self, name: &str) -> Result<(), BoxedError> {
         let mut tx = self.db.begin().await?;
         let channel = tx.channels().create(name).await?;
+        self.broadcaster.register_channel(&channel);
         tx.commit().await?;
 
-        self.broadcaster.register_channel(&channel)?;
         Ok(())
     }
 
@@ -50,7 +50,7 @@ impl<'a> Channels<'a> {
             .messages()
             .create(&login.id, channel, body, sent_at)
             .await?;
-        let message = Message::from_login(login, message)?;
+        let message = Message::from_login(login, message);
         tx.commit().await?;
 
         self.broadcaster.broadcast(channel, message);
@@ -122,33 +122,25 @@ impl Message {
         Ok(message)
     }
 
-    fn from_login(sender: &Login, message: StoredMessage) -> Result<Self, MessageError> {
-        if sender.id != message.sender {
-            // This functionally can't happen, but the funny thing about "This
-            // can never happen" comments is that they're usually wrong.
-            return Err(MessageError::LoginMismatched {
-                sender: sender.id.clone(),
-                message: message.sender,
-            });
-        }
+    fn from_login(sender: &Login, message: StoredMessage) -> Self {
+        // Panic as this logic is enforced by the caller anyways. This "can't
+        // happen," other than via programming mistakes, and cannot be fixed
+        // by config changes or changing user behaviours.
+        assert_eq!(
+            message.sender, sender.id,
+            "broadcast message must have the same sender ({}) as the stored message ({})",
+            sender.id, message.sender,
+        );
 
-        let message = Self {
+        Self {
             sender: sender.clone(),
             id: message.id,
             body: message.body,
             sent_at: message.sent_at,
-        };
-
-        Ok(message)
+        }
     }
 }
 
-#[derive(Debug, thiserror::Error)]
-enum MessageError {
-    #[error("sender login id {sender} did not match message login id {message}")]
-    LoginMismatched { sender: LoginId, message: LoginId },
-}
-
 // Clones will share the same senders collection.
 #[derive(Clone)]
 pub struct Broadcaster {
@@ -181,16 +173,15 @@ impl Broadcaster {
         }
     }
 
-    pub fn register_channel(&self, channel: &ChannelId) -> Result<(), RegisterError> {
+    // panic: if ``channel`` is already registered.
+    pub fn register_channel(&self, channel: &ChannelId) {
         match self.senders().entry(channel.clone()) {
             // This ever happening indicates a serious logic error.
-            Entry::Occupied(_) => return Err(RegisterError::Duplicate(channel.clone())),
+            Entry::Occupied(_) => panic!("duplicate channel registration for channel {channel}"),
             Entry::Vacant(entry) => {
                 entry.insert(Self::make_sender());
             }
         }
-
-        Ok(())
     }
 
     // panic: if ``channel`` has not been previously registered, and was not
@@ -230,9 +221,3 @@ impl Broadcaster {
         tx
     }
 }
-
-#[derive(Debug, thiserror::Error)]
-pub enum RegisterError {
-    #[error("duplicate broadcast registration for channel {0}")]
-    Duplicate(ChannelId),
-}
-- 
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