make Serializer and Deserializer pub and usable (#72)

* make Serializer/Deserializer pub

This is required when using serde_json_core with code that is
generic over the serde implementation, i.e. code that wants to
instantiate the Serializer/Deserializer, in the way done in
`de::from_slice` and `ser::to_slice`.

This also adds public getters for the Serializer.current_length
and Deserializer.index members.

Two obsolete/unused impls on the `Unreachable` have been removed.

* renames

* improve docs

* bump MSRV to 1.56.0

there is a MSRV bump somwhere in this dependency bump:

    Updating proc-macro2 v1.0.47 -> v1.0.66
    Updating quote v1.0.23 -> v1.0.32
    Updating serde v1.0.100 -> v1.0.175
    Updating serde_derive v1.0.100 -> v1.0.175
    Updating syn v1.0.109 -> v2.0.27

* fix wrong MSRV in README and src/lib.rs

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
 
         include:
           # Test MSRV
-          - rust: 1.55.0  # keep in sync with manifest rust-version
+          - rust: 1.56.0  # keep in sync with manifest rust-version
             TARGET: x86_64-unknown-linux-gnu
 
           # Test nightly but don't fail

CHANGELOG.md

@@ -11,6 +11,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Support for serializing tuple structs. These are serialized as JSON arrays,
   which matches `serde_json` behaviour.
+- `Serializer` and `Deserializer` are now `pub`.
+- Added `pub` `Serializer::end()` and `Deserializer::end()`.
+
+### Changed
+
+- Increase MSRV to 1.56.0 to work around dependency-MSRV issues (see #72)
 
 ## [v0.5.0] - 2022-11-04
 

Cargo.toml

@@ -4,7 +4,7 @@ categories = ["no-std"]
 description = "serde-json for no_std programs"
 documentation = "https://docs.rs/serde-json-core"
 edition = "2018"
-rust-version = "1.55.0"  # keep in sync with ci
+rust-version = "1.56.0"  # keep in sync with ci, src/lib.rs, and README
 keywords = ["serde", "json"]
 license = "MIT OR Apache-2.0"
 name = "serde-json-core"

README.md

@@ -12,7 +12,7 @@ This project is developed and maintained by the [rust-embedded-community].
 
 ## Minimum Supported Rust Version (MSRV)
 
-This crate is guaranteed to compile on stable Rust 1.51.0 and up. It *might*
+This crate is guaranteed to compile on stable Rust 1.56.0 and up. It *might*
 compile with older versions but that may change in any new patch release.
 
 ## License

src/de/mod.rs

@@ -79,21 +79,25 @@ pub enum Error {
 
 impl serde::de::StdError for Error {}
 
-pub(crate) struct Deserializer<'b> {
+/// A structure that deserializes Rust values from JSON in a buffer.
+pub struct Deserializer<'b> {
     slice: &'b [u8],
     index: usize,
 }
 
 impl<'a> Deserializer<'a> {
-    fn new(slice: &'a [u8]) -> Deserializer<'_> {
+    /// Create a new `Deserializer`
+    pub fn new(slice: &'a [u8]) -> Deserializer<'_> {
         Deserializer { slice, index: 0 }
     }
 
     fn eat_char(&mut self) {
         self.index += 1;
     }
 
-    fn end(&mut self) -> Result<usize> {
+    /// Check whether there is any unexpected data left in the buffer
+    /// and return the amount of data consumed
+    pub fn end(&mut self) -> Result<usize> {
         match self.parse_whitespace() {
             Some(_) => Err(Error::TrailingCharacters),
             None => Ok(self.index),

src/lib.rs

@@ -52,7 +52,7 @@
 //!
 //! # Minimum Supported Rust Version (MSRV)
 //!
-//! This crate is guaranteed to compile on stable Rust 1.51.0 and up. It *might* compile with older
+//! This crate is guaranteed to compile on stable Rust 1.56.0 and up. It *might* compile with older
 //! versions but that may change in any new patch release.
 
 #![deny(missing_docs)]

src/ser/mod.rs

@@ -48,19 +48,26 @@ impl fmt::Display for Error {
     }
 }
 
-pub(crate) struct Serializer<'a> {
+/// A structure that serializes Rust values as JSON into a buffer.
+pub struct Serializer<'a> {
     buf: &'a mut [u8],
     current_length: usize,
 }
 
 impl<'a> Serializer<'a> {
-    fn new(buf: &'a mut [u8]) -> Self {
+    /// Create a new `Serializer`
+    pub fn new(buf: &'a mut [u8]) -> Self {
         Serializer {
             buf,
             current_length: 0,
         }
     }
 
+    /// Return the current amount of serialized data in the buffer
+    pub fn end(&self) -> usize {
+        self.current_length
+    }
+
     fn push(&mut self, c: u8) -> Result<()> {
         if self.current_length < self.buf.len() {
             unsafe { self.push_unchecked(c) };
@@ -475,20 +482,8 @@ impl ser::Error for Error {
     }
 }
 
-pub(crate) enum Unreachable {}
-
-impl ser::SerializeTupleStruct for Unreachable {
-    type Ok = ();
-    type Error = Error;
-
-    fn serialize_field<T: ?Sized>(&mut self, _value: &T) -> Result<()> {
-        unreachable!()
-    }
-
-    fn end(self) -> Result<Self::Ok> {
-        unreachable!()
-    }
-}
+/// An unreachable type to fill the SerializeTupleVariant type
+pub enum Unreachable {}
 
 impl ser::SerializeTupleVariant for Unreachable {
     type Ok = ();
@@ -503,29 +498,6 @@ impl ser::SerializeTupleVariant for Unreachable {
     }
 }
 
-impl ser::SerializeMap for Unreachable {
-    type Ok = ();
-    type Error = Error;
-
-    fn serialize_key<T: ?Sized>(&mut self, _key: &T) -> Result<()>
-    where
-        T: ser::Serialize,
-    {
-        unreachable!()
-    }
-
-    fn serialize_value<T: ?Sized>(&mut self, _value: &T) -> Result<()>
-    where
-        T: ser::Serialize,
-    {
-        unreachable!()
-    }
-
-    fn end(self) -> Result<Self::Ok> {
-        unreachable!()
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use serde_derive::Serialize;