From e4025193ef0e26f57849271acd68a985451a8f47 Mon Sep 17 00:00:00 2001
From: Valentin <vakevk@gmail.com>
Date: Sat, 1 Feb 2025 12:21:55 +0100
Subject: [PATCH] in to_extend take collection by mutable reference

Currently the function takes the collection by value. Taking by mutable reference is better because it is more flexible. Whenever you have a value, you can also pass by mutable reference, but sometimes you only have a mutable reference and cannot pass by value.

This also fixes another problem with the current API: It keeps the collection on error. On success it returns it to the caller, but on error it does not. This makes the caller lose the collection.
---
 source/postcard/src/ser/flavors.rs | 14 +++++++-------
 source/postcard/src/ser/mod.rs     |  6 +++---
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/source/postcard/src/ser/flavors.rs b/source/postcard/src/ser/flavors.rs
index 7bca90ef..8434b9bd 100644
--- a/source/postcard/src/ser/flavors.rs
+++ b/source/postcard/src/ser/flavors.rs
@@ -213,25 +213,25 @@ impl IndexMut<usize> for Slice<'_> {
 }
 
 /// Wrapper over a [`core::iter::Extend<u8>`] that implements the flavor trait
-pub struct ExtendFlavor<T> {
-    iter: T,
+pub struct ExtendFlavor<'a, T> {
+    iter: &'a mut T,
 }
 
-impl<T> ExtendFlavor<T>
+impl<'a, T> ExtendFlavor<'a, T>
 where
     T: core::iter::Extend<u8>,
 {
     /// Create a new [`Self`] flavor from a given [`core::iter::Extend<u8>`]
-    pub fn new(iter: T) -> Self {
+    pub fn new(iter: &'a mut T) -> Self {
         Self { iter }
     }
 }
 
-impl<T> Flavor for ExtendFlavor<T>
+impl<T> Flavor for ExtendFlavor<'_, T>
 where
     T: core::iter::Extend<u8>,
 {
-    type Output = T;
+    type Output = ();
 
     #[inline(always)]
     fn try_push(&mut self, data: u8) -> Result<()> {
@@ -246,7 +246,7 @@ where
     }
 
     fn finalize(self) -> Result<Self::Output> {
-        Ok(self.iter)
+        Ok(())
     }
 }
 
diff --git a/source/postcard/src/ser/mod.rs b/source/postcard/src/ser/mod.rs
index e2fa32ac..a01fcdf0 100644
--- a/source/postcard/src/ser/mod.rs
+++ b/source/postcard/src/ser/mod.rs
@@ -262,11 +262,11 @@ where
 /// use postcard::to_extend;
 /// let mut vec = Vec::new();
 ///
-/// let ser = to_extend(&true, vec).unwrap();
-/// let vec = to_extend("Hi!", ser).unwrap();
+/// to_extend(&true, &mut vec).unwrap();
+/// to_extend("Hi!", &mut vec).unwrap();
 /// assert_eq!(&vec[0..5], &[0x01, 0x03, b'H', b'i', b'!']);
 /// ```
-pub fn to_extend<T, W>(value: &T, writer: W) -> Result<W>
+pub fn to_extend<T, W>(value: &T, writer: &mut W) -> Result<()>
 where
     T: Serialize + ?Sized,
     W: core::iter::Extend<u8>,