Make `SerializeOptions` non_exhaustive.

Add builder implementation similar to `LuaOptions` to set individual options.

src/serde/mod.rs

@@ -116,10 +116,8 @@ pub trait LuaSerdeExt<'lua> {
     /// fn main() -> Result<()> {
     ///     let lua = Lua::new();
     ///     let v = vec![1, 2, 3];
-    ///     lua.globals().set("v", lua.to_value_with(&v, SerializeOptions {
-    ///         set_array_metatable: false,
-    ///         ..SerializeOptions::default()
-    ///     })?)?;
+    ///     let options = SerializeOptions::new().set_array_metatable(false);
+    ///     lua.globals().set("v", lua.to_value_with(&v, options)?)?;
     ///
     ///     lua.load(r#"
     ///         assert(#v == 3 and v[1] == 1 and v[2] == 2 and v[3] == 3)

src/serde/ser.rs

@@ -21,11 +21,12 @@ pub struct Serializer<'lua> {
 
 /// A struct with options to change default serializer behaviour.
 #[derive(Debug, Clone, Copy)]
+#[non_exhaustive]
 pub struct Options {
     /// If true, sequence serialization to a Lua table will create table
     /// with the [`array_metatable`] attached.
     ///
-    /// Default: true
+    /// Default: **true**
     ///
     /// [`array_metatable`]: ../trait.LuaSerdeExt.html#tymethod.array_metatable
     pub set_array_metatable: bool,
@@ -33,7 +34,7 @@ pub struct Options {
     /// If true, serialize `None` (part of `Option` type) to [`null`].
     /// Otherwise it will be set to Lua [`Nil`].
     ///
-    /// Default: true
+    /// Default: **true**
     ///
     /// [`null`]: ../trait.LuaSerdeExt.html#tymethod.null
     /// [`Nil`]: ../../enum.Value.html#variant.Nil
@@ -42,7 +43,7 @@ pub struct Options {
     /// If true, serialize `Unit` (type of `()` in Rust) and Unit structs to [`null`].
     /// Otherwise it will be set to Lua [`Nil`].
     ///
-    /// Default: true
+    /// Default: **true**
     ///
     /// [`null`]: ../trait.LuaSerdeExt.html#tymethod.null
     /// [`Nil`]: ../../enum.Value.html#variant.Nil
@@ -59,6 +60,37 @@ impl Default for Options {
     }
 }
 
+impl Options {
+    /// Retruns a new instance of `Options` with default parameters.
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Sets [`set_array_metatable`] option.
+    ///
+    /// [`set_array_metatable`]: #structfield.set_array_metatable
+    pub fn set_array_metatable(mut self, enabled: bool) -> Self {
+        self.set_array_metatable = enabled;
+        self
+    }
+
+    /// Sets [`serialize_none_to_null`] option.
+    ///
+    /// [`serialize_none_to_null`]: #structfield.serialize_none_to_null
+    pub fn serialize_none_to_null(mut self, enabled: bool) -> Self {
+        self.serialize_none_to_null = enabled;
+        self
+    }
+
+    /// Sets [`serialize_unit_to_null`] option.
+    ///
+    /// [`serialize_unit_to_null`]: #structfield.serialize_unit_to_null
+    pub fn serialize_unit_to_null(mut self, enabled: bool) -> Self {
+        self.serialize_unit_to_null = enabled;
+        self
+    }
+}
+
 impl<'lua> Serializer<'lua> {
     /// Creates a new Lua Serializer with default options.
     pub fn new(lua: &'lua Lua) -> Self {

tests/serde.rs

@@ -241,10 +241,7 @@ fn test_to_value_with_options() -> Result<(), Box<dyn std::error::Error>> {
     // set_array_metatable
     let data = lua.to_value_with(
         &Vec::<i32>::new(),
-        SerializeOptions {
-            set_array_metatable: false,
-            ..SerializeOptions::default()
-        },
+        SerializeOptions::new().set_array_metatable(false),
     )?;
     globals.set("data", data)?;
     lua.load(
@@ -275,10 +272,7 @@ fn test_to_value_with_options() -> Result<(), Box<dyn std::error::Error>> {
     };
     let data2 = lua.to_value_with(
         &mydata,
-        SerializeOptions {
-            serialize_none_to_null: false,
-            ..SerializeOptions::default()
-        },
+        SerializeOptions::new().serialize_none_to_null(false),
     )?;
     globals.set("data2", data2)?;
     lua.load(
@@ -293,10 +287,7 @@ fn test_to_value_with_options() -> Result<(), Box<dyn std::error::Error>> {
     // serialize_unit_to_null
     let data3 = lua.to_value_with(
         &mydata,
-        SerializeOptions {
-            serialize_unit_to_null: false,
-            ..SerializeOptions::default()
-        },
+        SerializeOptions::new().serialize_unit_to_null(false),
     )?;
     globals.set("data3", data3)?;
     lua.load(