Add serde support for HashMapContext

Relates to #33

Cargo.toml

@@ -17,8 +17,10 @@ path = "src/lib.rs"
 
 [dependencies]
 serde = { version = "1", optional = true}
+serde_derive = { version = "1", optional = true}
 
 [features]
+serde_support = ["serde", "serde_derive"]
 
 [dev-dependencies]
 ron = "0.4"

README.md

@@ -318,12 +318,12 @@ Functions have a precedence of 190.
 
 ### [Serde](https://serde.rs)
 
-To use this crate with serde, the serde feature flag has to be set.
+To use this crate with serde, the `serde_support` feature flag has to be set.
 This can be done like this in the `Cargo.toml`:
 
 ```toml
 [dependencies]
-evalexpr = {version = "3", features = ["serde"]}
+evalexpr = {version = "3", features = ["serde_support"]}
 ```
 
 This crate implements `serde::de::Deserialize` for its type `Node` that represents a parsed expression tree.
@@ -349,6 +349,9 @@ match ron::de::from_str::<Node>(serialized_free) {
 
 With `serde`, expressions can be integrated into arbitrarily complex data.
 
+The crate also implements `Serialize` and `Deserialize` for the `HashMapContext`.
+But note that only the variables get serialized, not the functions.
+
 ## License
 
 This crate is primarily distributed under the terms of the MIT license.

src/context/mod.rs

@@ -1,9 +1,9 @@
 use std::collections::HashMap;
 
-use function::Function;
-use value::value_type::ValueType;
 use EvalexprError;
 use EvalexprResult;
+use function::Function;
+use value::value_type::ValueType;
 
 use crate::value::Value;
 
@@ -49,8 +49,11 @@ impl Context for EmptyContext {
 /// *Value and function mappings are stored independently, meaning that there can be a function and a value with the same identifier.*
 ///
 /// This context is type-safe, meaning that an identifier that is assigned a value of some type once cannot be assigned a value of another type.
+#[derive(Debug)]
+#[cfg_attr(feature = "serde_support", derive(Serialize, Deserialize))]
 pub struct HashMapContext {
     variables: HashMap<String, Value>,
+    #[cfg_attr(feature = "serde_support", serde(skip))]
     functions: HashMap<String, Function>,
 }
 

src/function/mod.rs

@@ -1,3 +1,5 @@
+use std::fmt;
+
 use error::{self, EvalexprResult};
 use value::Value;
 
@@ -47,3 +49,13 @@ impl Function {
         (self.function)(arguments)
     }
 }
+
+impl fmt::Debug for Function {
+    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        write!(
+            f,
+            "Function {{ argument_amount: {:?}, function: [...] }}",
+            self.argument_amount
+        )
+    }
+}

src/lib.rs

@@ -305,12 +305,12 @@
 //!
 //! ### [Serde](https://serde.rs)
 //!
-//! To use this crate with serde, the serde feature flag has to be set.
+//! To use this crate with serde, the `serde_support` feature flag has to be set.
 //! This can be done like this in the `Cargo.toml`:
 //!
 //! ```toml
 //! [dependencies]
-//! evalexpr = {version = "3", features = ["serde"]}
+//! evalexpr = {version = "3", features = ["serde_support"]}
 //! ```
 //!
 //! This crate implements `serde::de::Deserialize` for its type `Node` that represents a parsed expression tree.
@@ -336,6 +336,9 @@
 //!
 //! With `serde`, expressions can be integrated into arbitrarily complex data.
 //!
+//! The crate also implements `Serialize` and `Deserialize` for the `HashMapContext`.
+//! But note that only the variables get serialized, not the functions.
+//!
 //! ## License
 //!
 //! This crate is primarily distributed under the terms of the MIT license.
@@ -346,8 +349,11 @@
 
 #[cfg(test)]
 extern crate ron;
-#[cfg(feature = "serde")]
+#[cfg(feature = "serde_support")]
 extern crate serde;
+#[cfg(feature = "serde_support")]
+#[macro_use]
+extern crate serde_derive;
 
 pub use context::{Context, EmptyContext, HashMapContext};
 pub use error::{EvalexprError, EvalexprResult};
@@ -360,7 +366,7 @@ pub use value::{
 
 mod context;
 pub mod error;
-#[cfg(feature = "serde")]
+#[cfg(feature = "serde_support")]
 mod feature_serde;
 mod function;
 mod interface;

src/value/mod.rs

@@ -21,6 +21,7 @@ pub const EMPTY_VALUE: () = ();
 /// The value type used by the parser.
 /// Values can be of different subtypes that are the variants of this enum.
 #[derive(Clone, Debug, PartialEq)]
+#[cfg_attr(feature = "serde_support", derive(Serialize, Deserialize))]
 pub enum Value {
     /// A string value.
     String(String),