feat(metadata): mirror package features in features_v2

doc/book/src/reference/unstable.md

@@ -2407,6 +2407,20 @@ foo = { enables = [] }
 
 The required `enables` field is equivalent to the array-of-strings syntax.
 
+With `feature-metadata` enabled, `cargo metadata --format-version 1` includes a
+`features_v2` field alongside the existing `features` field. It mirrors every
+feature as an object with an `enables` array and other metadata fields:
+
+```json
+"features_v2": {
+  "foo": { "enables": [] },
+  "serde": {
+    "enables": ["dep:serde"],
+    "doc": "Enables support for serialization via serde."
+  }
+}
+```
+
 For other metadata fields, see the subsections below.
 
 ### feature-documentation

src/workspace/package.rs

@@ -10,7 +10,7 @@ use std::time::{Duration, Instant};
 
 use crate::util::data_structures::{HashMap, HashSet};
 use anyhow::Context as _;
-use cargo_util_schemas::manifest::{Hints, RustVersion};
+use cargo_util_schemas::manifest::{FeatureDefinition, Hints, RustVersion};
 use futures::FutureExt;
 use futures::TryStreamExt;
 use futures::stream::FuturesUnordered;
@@ -31,8 +31,8 @@ use crate::util::network::retry::{Retry, RetryResult};
 use crate::util::{self, GlobalContext, Progress, ProgressStyle, internal};
 use crate::workspace::dependency::DepKind;
 use crate::workspace::{
-    CliUnstable, Dependency, Features, Manifest, PackageId, PackageIdSpec, SerializedDependency,
-    SourceId, Target,
+    CliUnstable, Dependency, Feature, Features, Manifest, PackageId, PackageIdSpec,
+    SerializedDependency, SourceId, Target,
 };
 use crate::workspace::{Summary, Workspace};
 
@@ -78,6 +78,8 @@ pub struct SerializedPackage {
     dependencies: Vec<SerializedDependency>,
     targets: Vec<Target>,
     features: BTreeMap<InternedString, Vec<InternedString>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    features_v2: Option<BTreeMap<InternedString, SerializedFeature>>,
     manifest_path: PathBuf,
     metadata: Option<toml::Value>,
     publish: Option<Vec<String>>,
@@ -98,6 +100,13 @@ pub struct SerializedPackage {
     hints: Option<Hints>,
 }
 
+#[derive(Serialize)]
+struct SerializedFeature {
+    enables: Vec<InternedString>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    doc: Option<String>,
+}
+
 impl Package {
     /// Creates a package from a manifest and its location.
     pub fn new(manifest: Manifest, manifest_path: &Path) -> Package {
@@ -210,12 +219,30 @@ impl Package {
             .filter(|t| t.src_path().is_path())
             .cloned()
             .collect();
-        // Convert Vec<FeatureValue> to Vec<InternedString>
-        let crate_features = summary
-            .features()
-            .iter()
-            .map(|(k, v)| (*k, v.iter().map(|fv| fv.to_string().into()).collect()))
-            .collect();
+        let manifest_features = self.manifest().normalized_toml().features();
+        let mut crate_features = BTreeMap::new();
+        let mut features_v2 = cargo_features
+            .is_enabled(Feature::feature_metadata())
+            .then(BTreeMap::new);
+        for (k, v) in summary.features() {
+            let enables: Vec<InternedString> = v.iter().map(|fv| fv.to_string().into()).collect();
+            if let Some(features_v2) = &mut features_v2 {
+                let doc = manifest_features
+                    .and_then(|mf| mf.get(k.as_str()))
+                    .and_then(|feat_def| match feat_def {
+                        FeatureDefinition::Metadata(meta) => meta.doc.clone(),
+                        FeatureDefinition::Array(_) => None,
+                    });
+                features_v2.insert(
+                    *k,
+                    SerializedFeature {
+                        enables: enables.clone(),
+                        doc,
+                    },
+                );
+            }
+            crate_features.insert(*k, enables);
+        }
 
         SerializedPackage {
             name: package_id.name(),
@@ -232,6 +259,7 @@ impl Package {
                 .collect(),
             targets,
             features: crate_features,
+            features_v2,
             manifest_path: self.manifest_path().to_path_buf(),
             metadata: self.manifest().custom_metadata().cloned(),
             authors: manmeta.authors.clone(),

tests/testsuite/metadata.rs

@@ -4984,3 +4984,77 @@ fn metadata_ignores_build_target_configuration() -> anyhow::Result<()> {
     );
     Ok(())
 }
+
+#[cargo_test]
+fn cargo_metadata_features_v2() {
+    Package::new("serde", "1.0.0").publish();
+    Package::new("log", "1.0.0").publish();
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                cargo-features = ["feature-metadata"]
+
+                [package]
+                name = "foo"
+                version = "0.5.0"
+                edition = "2015"
+
+                [dependencies]
+                serde = { version = "1.0.0", optional = true }
+                log = { version = "1.0.0", optional = true }
+
+                [features]
+                default = ["serde"]
+                empty = []
+                legacy = ["empty"]
+                serde = { enables = ["dep:serde"], doc = "Enables support for serialization via serde." }
+                table_empty = { enables = [] }
+                table_without_doc = { enables = ["empty"] }
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    p.cargo("metadata --format-version 1")
+        .masquerade_as_nightly_cargo(&["feature-metadata"])
+        .with_stdout_data(
+            str![[r#"
+{
+  "packages": [
+    {
+      "name": "foo",
+      "features": {
+        "default": ["serde"],
+        "empty": [],
+        "legacy": ["empty"],
+        "log": ["dep:log"],
+        "serde": ["dep:serde"],
+        "table_empty": [],
+        "table_without_doc": ["empty"]
+      },
+      "features_v2": {
+        "default": { "enables": ["serde"] },
+        "empty": { "enables": [] },
+        "legacy": { "enables": ["empty"] },
+        "log": { "enables": ["dep:log"] },
+        "serde": {
+          "enables": ["dep:serde"],
+          "doc": "Enables support for serialization via serde."
+        },
+        "table_empty": { "enables": [] },
+        "table_without_doc": { "enables": ["empty"] }
+      },
+      "...": "{...}"
+    },
+    "{...}",
+    "{...}"
+  ],
+  "...": "{...}"
+}
+"#]]
+            .is_json(),
+        )
+        .run();
+}