Add support for package.metadata table

Cargo.toml

@@ -20,3 +20,7 @@ version = "0.9"
 [dev-dependencies]
 clap = "2.26.0"
 docopt = "0.8.1"
+
+[package.metadata.cargo_metadata_test]
+some_field = true
+other_field = "foo"

src/lib.rs

@@ -155,6 +155,33 @@ pub struct Package {
  pub features: HashMap<String, Vec<String>>,
  /// Path containing the `Cargo.toml`
  pub manifest_path: String,
+ /// Contents of the free form package.metadata section
+ ///
+ /// This contents can be serialized to a struct using serde:
+ ///
+ /// ```rust
+ /// #[macro_use]
+ /// extern crate serde_json;
+ /// #[macro_use]
+ /// extern crate serde_derive;
+ ///
+ /// #[derive(Debug, Deserialize)]
+ /// struct SomePackageMetadata {
+ /// some_value: i32,
+ /// }
+ ///
+ /// fn main() {
+ /// let value = json!({
+ /// "some_value": 42,
+ /// });
+ ///
+ /// let package_metadata: SomePackageMetadata = serde_json::from_value(value).unwrap();
+ /// assert_eq!(package_metadata.some_value, 42);
+ /// }
+ ///
+ /// ```
+ #[serde(default)]
+ pub metadata: serde_json::Value,
  #[doc(hidden)]
  #[serde(skip)]
  __do_not_match_exhaustively: (),

tests/selftest.rs

@@ -2,13 +2,23 @@ extern crate cargo_metadata;
 extern crate semver;
 extern crate serde_json;
 
+#[macro_use]
+extern crate serde_derive;
+
 use std::env::current_dir;
 use std::path::Path;
+use std::env;
 
 use semver::Version;
 
 use cargo_metadata::{Error, ErrorKind};
 
+#[derive(Debug, PartialEq, Eq, Deserialize)]
+struct TestPackageMetadata {
+ some_field: bool,
+ other_field: String,
+}
+
 #[test]
 fn metadata() {
  let metadata = cargo_metadata::metadata(None).unwrap();
@@ -28,6 +38,22 @@ fn metadata() {
  assert_eq!(metadata.packages[0].targets[1].name, "selftest");
  assert_eq!(metadata.packages[0].targets[1].kind[0], "test");
  assert_eq!(metadata.packages[0].targets[1].crate_types[0], "bin");
+
+ // Hack until the package metadata field reaches the stable channel (in version 1.27).
+ if env::var("TRAVIS_RUST_VERSION") != Ok("stable".into()) {
+ let package_metadata = &metadata.packages[0].metadata.as_object()
+ .expect("package.metadata must be a table. \
+ NOTE: This test currently only works on the beta and nightly channel.");
+ assert_eq!(package_metadata.len(), 1);
+
+ let value = package_metadata.get("cargo_metadata_test").unwrap();
+ let test_package_metadata: TestPackageMetadata = serde_json::from_value(value.clone())
+ .unwrap();
+ assert_eq!(test_package_metadata, TestPackageMetadata {
+ some_field: true,
+ other_field: "foo".into(),
+ });
+ }
 }
 
 #[test]