Implement serde::Serialize and serde::Deserialize.

Fixes #37.

.appveyor.yml

@@ -54,8 +54,8 @@ install:
 ## Build Script ##
 build: false
 test_script:
-  - cargo build --verbose
-  - cargo test --verbose
+  - cargo build --verbose --all-features --tests
+  - cargo test --verbose --features serde
 
 notifications:
     - provider: Email

.travis.yml

@@ -30,8 +30,8 @@ before_script: |
   (test $(grep "cargo-travis" /home/travis/.cargo/.crates.toml | sed -r "s/\"cargo-travis ([^\ ]+).+/\1/") = $(cargo search cargo-travis --limit 1 | sed -r "s/cargo-travis \(([^\)]+)\).+/\1/") || cargoo install cargo-travis --force)
 
 script: |
-  cargo build --verbose &&
-  (test "$TRAVIS_RUST_VERSION" == "1.20.0" || cargo test --verbose)
+  cargo build --verbose --all-features --tests &&
+  (test "$TRAVIS_RUST_VERSION" == "1.20.0" || cargo test --verbose --features serde)
 
 after_success: |
   test "$TRAVIS_RUST_VERSION" != "stable" || cargo coveralls

CHANGELOG.md

@@ -14,6 +14,8 @@
 ### Added
  * [#26](https://github.com/iliekturtles/uom/issues/26) Implement `num::Zero`.
  * [#35](https://github.com/iliekturtles/uom/issues/35) Implement `num::Saturating`.
+ * [#37](https://github.com/iliekturtles/uom/issues/35) Implement `serde::Serialize` and
+   `serde::Deserialize`. Disabled by default. Enabled with the `use_serde` feature.
 
 ## [v0.16.0] — 2017-12-21
 This release contains significant changes in order to support underlying storage types that

Cargo.toml

@@ -22,11 +22,13 @@ maintenance = { status = "actively-developed" }
 
 [dependencies]
 num = "0.1"
+serde = { version = "1.0", optional = true, default-features = false }
 typenum = "1.9.0"
 
 [dev-dependencies]
 approx = "0.1.1"
 quickcheck = "0.5.0"
+serde_json = "1.0"
 static_assertions = "0.2.5"
 
 [features]
@@ -51,6 +53,11 @@ f32 = []
 f64 = []
 si = []
 std = []
+# The `use_serde` feature exists so that, in the future, other dependency features like num/serde
+# can be added. However, num/serde is currently left out because it has not yet been updated to
+# Serde 1.0. It is also necessary to name the feature something other than `serde` because of a
+# cargo bug: https://github.com/rust-lang/cargo/issues/1286
+use_serde = ["serde"]
 
 [[example]]
 name = "base"

README.md

@@ -63,10 +63,10 @@ See the [examples](examples) directory for more advanced usage:
 
 ## Features
 `uom` has multiple `Cargo` features for controlling available underlying storage types, the
-inclusion of the pre-built [International System of Units][si] (SI), and `no_std` functionality. The
-features are described below. `f32`, `f64`, `std`, and `si` are enabled by default. Features can be
-cherry-picked by using the `--no-default-features` and `--features "..."` flags when compiling `uom`
-or specifying features in Cargo.toml:
+inclusion of the pre-built [International System of Units][si] (SI), support for [Serde][serde],
+and `no_std` functionality. The features are described below. `f32`, `f64`, `std`, and `si` are
+enabled by default. Features can be cherry-picked by using the `--no-default-features` and
+`--features "..."` flags when compiling `uom` or specifying features in Cargo.toml:
 
 ```toml
 [dependencies]
@@ -80,6 +80,7 @@ uom = {
         "rational", "rational32", "rational64", "bigrational", # Integer ratio storage types.
         "f32", "f64", # Floating point storage types.
         "si", "std", # Built-in SI system and std library support.
+        "use_serde", # Serde support.
     ]
 }
 ```
@@ -92,8 +93,11 @@ uom = {
    default.
  * `std` -- Feature to compile with standard library support. Disabling this feature compiles `uom`
    with `no_std`. Enabled by default.
+ * `use_serde` -- Feature to enable support for serialization and deserialization of quantities
+   with the [Serde][serde] crate. Disabled by default.
 
 [si]: http://jcgm.bipm.org/vim/en/1.16.html
+[serde]: https://serde.rs/
 
 ## Design
 Rather than working with [measurement units](http://jcgm.bipm.org/vim/en/1.9.html) (meter,

src/lib.rs

@@ -52,10 +52,11 @@
 //!
 //! ## Features
 //! `uom` has multiple `Cargo` features for controlling available underlying storage types, the
-//! inclusion of the pre-built [International System of Units][si] (SI), and `no_std` functionality.
-//! The features are described below. `f32`, `f64`, `std`, and `si` are enabled by default. Features
-//! can be cherry-picked by using the `--no-default-features` and `--features "..."` flags when
-//! compiling `uom` or specifying features in Cargo.toml:
+//! inclusion of the pre-built [International System of Units][si] (SI), support for
+//! [Serde][serde], and `no_std` functionality. The features are described below. `f32`, `f64`,
+//! `std`, and `si` are enabled by default. Features can be cherry-picked by using the
+//! `--no-default-features` and `--features "..."` flags when compiling `uom` or specifying
+//! features in Cargo.toml:
 //!
 //! ```toml
 //! [dependencies]
@@ -69,6 +70,7 @@
 //!         "rational", "rational32", "rational64", "bigrational", # Integer ratio storage types.
 //!         "f32", "f64", # Floating point storage types.
 //!         "si", "std", # Built-in SI system and std library support.
+//!         "use_serde", # Serde support.
 //!     ]
 //! }
 //! ```
@@ -81,8 +83,11 @@
 //!    default.
 //!  * `std` -- Feature to compile with standard library support. Disabling this feature compiles
 //!    `uom` with `no_std`. Enabled by default.
+//!  * `use_serde` -- Feature to enable support for serialization and deserialization of quantities
+//!    with the [Serde][serde] crate. Disabled by default.
 //!
 //! [si]: http://jcgm.bipm.org/vim/en/1.16.html
+//! [serde]: https://serde.rs/
 //!
 //! ## Design
 //! Rather than working with [measurement units](http://jcgm.bipm.org/vim/en/1.9.html) (meter,
@@ -156,6 +161,10 @@ compile_error!("A least one underlying storage type must be enabled. See the fea
 #[doc(hidden)]
 pub extern crate num;
 
+#[doc(hidden)]
+#[cfg(feature = "serde")]
+pub extern crate serde;
+
 #[doc(hidden)]
 pub extern crate typenum;
 
@@ -165,6 +174,8 @@ extern crate approx;
 #[cfg(test)]
 #[macro_use]
 extern crate quickcheck;
+#[cfg(all(test, feature = "serde"))]
+extern crate serde_json;
 #[cfg(test)]
 #[macro_use]
 extern crate static_assertions;

src/system.rs

@@ -873,6 +873,42 @@ macro_rules! system {
             }
         }
 
+        #[cfg(feature = "serde")]
+        impl<D, U, V> $crate::serde::Serialize for Quantity<D, U, V>
+        where
+            D: Dimension + ?Sized,
+            U: Units<V> + ?Sized,
+            V: $crate::num::Num + $crate::Conversion<V> + $crate::serde::Serialize,
+        {
+            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+            where
+                S: $crate::serde::Serializer
+            {
+                self.value.serialize(serializer)
+            }
+        }
+
+        #[cfg(feature = "serde")]
+        impl<'de, D, U, V> $crate::serde::Deserialize<'de> for Quantity<D, U, V>
+        where
+            D: Dimension + ?Sized,
+            U: Units<V> + ?Sized,
+            V: $crate::num::Num + $crate::Conversion<V> + $crate::serde::Deserialize<'de>,
+        {
+            fn deserialize<De>(deserializer: De) -> Result<Self, De::Error>
+            where
+                De: $crate::serde::Deserializer<'de>,
+            {
+                let value: V = $crate::serde::Deserialize::deserialize(deserializer)?;
+
+                Ok(Quantity {
+                    dimension: $crate::lib::marker::PhantomData,
+                    units: $crate::lib::marker::PhantomData,
+                    value,
+                })
+            }
+        }
+
         /// Macro to implement [`quantity`](si/struct.Quantity.html) type aliases for a specific
         /// [system of units][units] and value storage type.
         ///

src/tests.rs

@@ -7,6 +7,8 @@ use num::{Float, FromPrimitive, One, Saturating, Signed, Zero};
 use quickcheck::TestResult;
 use lib::fmt::Debug;
 use lib::marker::PhantomData;
+#[cfg(feature = "serde")]
+use serde_json;
 #[allow(unused_imports)]
 use typenum::{N1, P1, P2, P3, Z0};
 
@@ -710,7 +712,7 @@ mod system_macro {
         }
     }
 
-    mod op_assign {
+    mod primitive {
         storage_types! {
             types: Float, PrimInt;
 
@@ -781,6 +783,28 @@ mod system_macro {
 
                     TestResult::from_bool(Test::approx_eq(&f, &v.get(meter)))
                 }
+
+                // These serde tests can't be run against num-backed numeric backends because the num
+                // crate hasn't been updated to Serde 1.0 yet.
+                #[cfg(feature = "serde")]
+                #[allow(trivial_casts)]
+                fn serde_serialize(v: A<V>) -> bool {
+                    let m = Length::new::<meter>((*v).clone());
+                    let json_f = serde_json::to_string(&*v).expect("Must be able to serialize num");
+                    let json_q = serde_json::to_string(&m).expect("Must be able to serialize Quantity");
+
+                    json_f == json_q
+                }
+
+                #[cfg(feature = "serde")]
+                #[allow(trivial_casts)]
+                fn serde_deserialize(v: A<V>) -> bool {
+                    let json_f = serde_json::to_string(&*v).expect("Must be able to serialize num");
+                    let length: Length = serde_json::from_str(&json_f)
+                        .expect("Must be able to deserialize Quantity");
+
+                    Test::approx_eq(&*v, &length.get(meter))
+                }
             }
         }
     }