[pve-devel] [PATCH proxmox 2/2] notify: sendmail: smtp: list email recipients in stable order

[Lukas Wagner]

The get_recipients function, which is used by the smtp and sendmail
target, is used to look up user's email addresses from the user
configuration while avoiding duplicate recipients at the same time.

Due to the use of a HashSet to avoid duplicate addresses, the order of
the email addresses was not stable. Only a minor cosmetic detail, but
using the same order as defined in the target config is definitely
nicer, which is achieved by using a plain old Vec instead, adding
.contains(...) checks as needed.

Also add some basic rust doc and test while at it.

Signed-off-by: Lukas Wagner <l.wagner at proxmox.com>
---
 proxmox-notify/src/context/test.rs          | 10 ++++-
 proxmox-notify/src/endpoints/common/mail.rs | 49 ++++++++++++++++++---
 2 files changed, 51 insertions(+), 8 deletions(-)

diff --git a/proxmox-notify/src/context/test.rs b/proxmox-notify/src/context/test.rs
index 13ef6eae..2c236b4c 100644
--- a/proxmox-notify/src/context/test.rs
+++ b/proxmox-notify/src/context/test.rs
@@ -6,8 +6,14 @@ use crate::Error;
 pub struct TestContext;
 
 impl Context for TestContext {
-    fn lookup_email_for_user(&self, _user: &str) -> Option<String> {
-        Some("test at example.com".into())
+    fn lookup_email_for_user(&self, user: &str) -> Option<String> {
+        user.split_once('@').and_then(|(user, realm)| {
+            if realm == "pve" {
+                Some(format!("{user}@example.com"))
+            } else {
+                None
+            }
+        })
     }
 
     fn default_sendmail_author(&self) -> String {
diff --git a/proxmox-notify/src/endpoints/common/mail.rs b/proxmox-notify/src/endpoints/common/mail.rs
index 7a2de59f..074712cf 100644
--- a/proxmox-notify/src/endpoints/common/mail.rs
+++ b/proxmox-notify/src/endpoints/common/mail.rs
@@ -1,18 +1,25 @@
-use std::collections::HashSet;
-
 use crate::context;
 
-pub(crate) fn get_recipients(email_addrs: &[String], users: &[String]) -> HashSet<String> {
-    let mut recipients = HashSet::new();
+/// Get list of email recipients from a list of email addresses and users.
+///
+/// Any user passed in the user list will be looked up in the user configuration to
+/// obtain this user's email address. The list of returned email addresses does
+/// not contain any duplicates.
+pub(crate) fn get_recipients(email_addrs: &[String], users: &[String]) -> Vec<String> {
+    let mut recipients = Vec::new();
 
     for addr in email_addrs {
-        recipients.insert(addr.clone());
+        if !recipients.contains(addr) {
+            recipients.push(addr.clone());
+        }
     }
 
     for user in users {
         match context::context().lookup_email_for_user(user) {
             Some(address) => {
-                recipients.insert(address);
+                if !recipients.contains(&address) {
+                    recipients.push(address);
+                }
             }
             None => tracing::warn!(
                 "'{user}' does not have a configured email address in the user configuration - \
@@ -22,3 +29,33 @@ pub(crate) fn get_recipients(email_addrs: &[String], users: &[String]) -> HashSe
     }
     recipients
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_get_recipients() {
+        let emails = Vec::from(
+            [
+                "test1 at example.com",
+                "test2 at example.com",
+                "test2 at example.com",
+            ]
+            .map(Into::into),
+        );
+        let users =
+            Vec::from(["user1 at pve", "user2 at pve", "user2 at pve", "user3 at invalid"].map(Into::into));
+
+        let expected = [
+            "test1 at example.com",
+            "test2 at example.com",
+            "user1 at example.com",
+            "user2 at example.com",
+        ];
+
+        let addrs = get_recipients(&emails, &users);
+
+        assert_eq!(addrs, expected);
+    }
+}
-- 
2.47.2