Add a proc_macro component to serde_with

A proc_macro is required to implement skip_serializing_null from
dtolnay/request-for-implementation#18

Expose the macro crate in serde_with

* Add a "macros"-feature to disable compiling proc_macros
* Add the feature to the testing matrix

.travis.yml

@@ -70,7 +70,7 @@ before_script:
 script:
   - set -e
   - |
-    for FEATURES_COMMAND in "--no-default-features" "" "--features=chrono" "--features=json" "--all-features"
+    for FEATURES_COMMAND in "--no-default-features" "" "--features=chrono" "--features=json" "--features=macros" "--all-features"
     do
       cargo build --verbose --all ${FEATURES_COMMAND}
       # skip this step if clippy is not available, e.g., bad nightly

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+### Added
+
+* Add `skip_serializing_null` attribute, which adds `#[serde(skip_serializing_if = "Option::is_none")]` for each Option in a struct.
+    This is helpfull for APIs which have many optional fields.
+
 ## [1.2.0]
 
 ### Added

Cargo.toml

@@ -1,3 +1,8 @@
+[workspace]
+members = [
+    "serde_with_macros",
+]
+
 [package]
 name = "serde_with"
 version = "1.2.0"
@@ -26,12 +31,15 @@ codecov = { repository = "jonasbb/serde_with", branch = "master", service = "git
 maintenance = { status = "actively-developed" }
 
 [features]
+default = [ "macros" ]
 json = [ "serde_json" ]
+macros = [ "serde_with_macros" ]
 
 [dependencies]
 chrono = { version = "0.4.1", features = [ "serde" ], optional = true }
 serde = "1.0.75"
 serde_json = { version = "1.0.1", optional = true }
+serde_with_macros = { path = "./serde_with_macros", version = "0.1.0", optional = true}
 
 [dev-dependencies]
 fnv = "1.0.6"

serde_with_macros/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "serde_with_macros"
+version = "0.1.0"
+authors = ["jonasbb"]
+
+description = "proc-macro library for serde_with"
+documentation = "https://docs.rs/serde_with_macros/"
+repository = "https://github.com/jonasbb/serde_with/serde_with_macros"
+readme = "README.md"
+keywords = ["serde", "utilities", "serialization", "deserialization"]
+license = "MIT/Apache-2.0"
+
+[lib]
+proc-macro = true
+
+[badges]
+travis-ci = { repository = "jonasbb/serde_with", branch = "master" }
+codecov = { repository = "jonasbb/serde_with", branch = "master", service = "github" }
+maintenance = { status = "actively-developed" }
+
+[dependencies]

serde_with_macros/LICENSE-APACHE

@@ -0,0 +1 @@
+../LICENSE-APACHE

serde_with_macros/LICENSE-MIT

@@ -0,0 +1 @@
+../LICENSE-MIT

serde_with_macros/README.md

@@ -0,0 +1 @@
+../README.md

src/lib.rs

@@ -83,6 +83,8 @@ extern crate chrono as chrono_crate;
 pub extern crate serde;
 #[cfg(feature = "json")]
 extern crate serde_json;
+#[cfg(feature = "macros")]
+extern crate serde_with_macros;
 
 #[cfg(feature = "chrono")]
 pub mod chrono;
@@ -94,6 +96,11 @@ pub mod rust;
 #[doc(hidden)]
 pub mod with_prefix;
 
+// Re-Export all proc_macros, as these should be seen as part of the serde_with crate
+#[cfg(feature = "macros")]
+#[doc(inline)]
+pub use serde_with_macros::*;
+
 /// Separator for string-based collection de/serialization
 pub trait Separator {
     /// Return the string delimiting two elements in the string-based collection