Add a Newtype for custom states

This allow us to do some sanity checks on them.

src/notify/error.rs

@@ -77,9 +77,9 @@ pub enum FdNameError {
 impl Display for FdNameError {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            FdNameError::TooLong { length, name } => write!(f, "the file descriptor name {name:?} is too long (is {length} characters and should be less than 255)"),
-            FdNameError::NotAsciiNonControl { disallowed_char, name } => write!(f, "the file descriptor name {name:?} contains invalid character '{disallowed_char}' (only ASCII allowed)"),
-            FdNameError::ContainColon(name) => write!(f, "the file descriptor name {name:?} contains a colon (':') which isn't allowed"),
+            Self::TooLong { length, name } => write!(f, "the file descriptor name {name:?} is too long (is {length} characters and should be less than 255)"),
+            Self::NotAsciiNonControl { disallowed_char, name } => write!(f, "the file descriptor name {name:?} contains invalid character '{disallowed_char}' (only ASCII allowed)"),
+            Self::ContainColon(name) => write!(f, "the file descriptor name {name:?} contains a colon (':') which isn't allowed"),
         }
     }
 }
@@ -102,3 +102,22 @@ impl Display for StatusLineError {
 }
 
 impl Error for StatusLineError {}
+
+#[derive(Debug)]
+pub enum OtherStateError {
+    TooManyLines,
+    NoAssignement,
+    DisallowedState(String),
+}
+
+impl Display for OtherStateError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::DisallowedState(state) => write!(f, "The state assignement {state:?} isn't allowed."),
+            Self::NoAssignement => write!(f, "No assignement was found in provided custom state."),
+            Self::TooManyLines => write!(f, "States cannot contains newlines (they are newline separated in the underlying protocol).")
+        }
+    }
+}
+
+impl Error for OtherStateError {}

src/notify/mod.rs

@@ -216,7 +216,7 @@ pub enum NotifyState<'a> {
     /// The main process ID of the service, in case of forking applications.
     Mainpid(libc::pid_t),
     /// Custom state change, as a `KEY=VALUE` string.
-    Other(&'a str),
+    Other(types::OtherState<'a>),
     /// Service startup is finished.
     Ready,
     /// Service is reloading.
@@ -247,7 +247,7 @@ impl<'a> Display for NotifyState<'a> {
             NotifyState::FdStoreRemove => f.write_str("FDSTOREREMOVE=1"),
             NotifyState::FdpollDisable => f.write_str("FDPOLL=0"),
             NotifyState::Mainpid(pid) => write!(f, "MAINPID={pid}"),
-            NotifyState::Other(message) => Display::fmt(message, f),
+            NotifyState::Other(types::OtherState(message)) => f.write_str(message),
             NotifyState::Ready => f.write_str("READY=1"),
             NotifyState::Reloading => f.write_str("RELOADING=1"),
             NotifyState::Status(types::StatusLine(status)) => write!(f, "STATUS={status}"),

src/notify/types.rs

@@ -102,3 +102,32 @@ impl AsRef<str> for BusError<'_> {
         self.0
     }
 }
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct OtherState<'a>(pub(super) &'a str);
+
+impl<'a> TryFrom<&'a str> for OtherState<'a> {
+    type Error = error::OtherStateError;
+
+    fn try_from(value: &'a str) -> Result<Self, Self::Error> {
+        if value.contains('\n') {
+            return Err(Self::Error::TooManyLines);
+        }
+
+        if !value.contains('=') {
+            return Err(Self::Error::NoAssignement);
+        }
+
+        if value == "BARRIER=1" {
+            return Err(Self::Error::DisallowedState(String::from(value)));
+        }
+
+        Ok(Self(value))
+    }
+}
+
+impl AsRef<str> for OtherState<'_> {
+    fn as_ref(&self) -> &str {
+        self.0
+    }
+}