-- Part 1 of RFC2906

src/cargo/core/compiler/standard_lib.rs

@@ -65,6 +65,7 @@ pub fn resolve_std<'cfg>(
         &Some(members),
         /*default_members*/ &None,
         /*exclude*/ &None,
+        /*inheritable*/ &None,
         /*custom_metadata*/ &None,
     ));
     let virtual_manifest = crate::core::VirtualManifest::new(

src/cargo/core/features.rs

@@ -412,6 +412,9 @@ features! {
 
     // Allow specifying rustflags directly in a profile
     (unstable, profile_rustflags, "", "reference/unstable.html#profile-rustflags-option"),
+
+    // Allow specifying rustflags directly in a profile
+    (unstable, workspace_inheritance, "", "reference/unstable.html#workspace-inheritance"),
 }
 
 pub struct Feature {

src/cargo/core/mod.rs

@@ -10,7 +10,9 @@ pub use self::resolver::{Resolve, ResolveVersion};
 pub use self::shell::{Shell, Verbosity};
 pub use self::source::{GitReference, Source, SourceId, SourceMap};
 pub use self::summary::{FeatureMap, FeatureValue, Summary};
-pub use self::workspace::{MaybePackage, Workspace, WorkspaceConfig, WorkspaceRootConfig};
+pub use self::workspace::{
+    InheritableFields, MaybePackage, Workspace, WorkspaceConfig, WorkspaceRootConfig,
+};
 
 pub mod compiler;
 pub mod dependency;

src/cargo/core/workspace.rs

@@ -22,7 +22,9 @@ use crate::sources::{PathSource, CRATES_IO_INDEX, CRATES_IO_REGISTRY};
 use crate::util::errors::{CargoResult, ManifestError};
 use crate::util::interning::InternedString;
 use crate::util::lev_distance;
-use crate::util::toml::{read_manifest, TomlDependency, TomlProfiles};
+use crate::util::toml::{
+    read_manifest, StringOrBool, TomlDependency, TomlProfiles, VecStringOrBool,
+};
 use crate::util::{config::ConfigRelativePath, Config, Filesystem, IntoUrl};
 use cargo_util::paths;
 
@@ -123,6 +125,15 @@ pub enum WorkspaceConfig {
     Member { root: Option<String> },
 }
 
+impl WorkspaceConfig {
+    pub fn inheritable(&self) -> Option<&InheritableFields> {
+        match self {
+            WorkspaceConfig::Root(root) => Some(&root.inheritable_fields),
+            WorkspaceConfig::Member { .. } => None,
+        }
+    }
+}
+
 /// Intermediate configuration of a workspace root in a manifest.
 ///
 /// Knows the Workspace Root path, as well as `members` and `exclude` lists of path patterns, which
@@ -133,6 +144,7 @@ pub struct WorkspaceRootConfig {
     members: Option<Vec<String>>,
     default_members: Option<Vec<String>>,
     exclude: Vec<String>,
+    inheritable_fields: InheritableFields,
     custom_metadata: Option<toml::Value>,
 }
 
@@ -1567,6 +1579,7 @@ impl WorkspaceRootConfig {
         members: &Option<Vec<String>>,
         default_members: &Option<Vec<String>>,
         exclude: &Option<Vec<String>>,
+        inheritable: &Option<InheritableFields>,
         custom_metadata: &Option<toml::Value>,
     ) -> WorkspaceRootConfig {
         WorkspaceRootConfig {
@@ -1574,10 +1587,10 @@ impl WorkspaceRootConfig {
             members: members.clone(),
             default_members: default_members.clone(),
             exclude: exclude.clone().unwrap_or_default(),
+            inheritable_fields: inheritable.clone().unwrap_or_default(),
             custom_metadata: custom_metadata.clone(),
         }
     }
-
     /// Checks the path against the `excluded` list.
     ///
     /// This method does **not** consider the `members` list.
@@ -1641,3 +1654,121 @@ impl WorkspaceRootConfig {
         Ok(res)
     }
 }
+
+/// A group of fields that are inheritable by members of the workspace
+#[derive(Clone, Debug, Default)]
+pub struct InheritableFields {
+    dependencies: Option<BTreeMap<String, TomlDependency>>,
+    version: Option<semver::Version>,
+    authors: Option<Vec<String>>,
+    description: Option<String>,
+    homepage: Option<String>,
+    documentation: Option<String>,
+    readme: Option<StringOrBool>,
+    keywords: Option<Vec<String>>,
+    categories: Option<Vec<String>>,
+    license: Option<String>,
+    license_file: Option<String>,
+    repository: Option<String>,
+    publish: Option<VecStringOrBool>,
+    edition: Option<String>,
+    badges: Option<BTreeMap<String, BTreeMap<String, String>>>,
+}
+
+impl InheritableFields {
+    pub fn new(
+        dependencies: Option<BTreeMap<String, TomlDependency>>,
+        version: Option<semver::Version>,
+        authors: Option<Vec<String>>,
+        description: Option<String>,
+        homepage: Option<String>,
+        documentation: Option<String>,
+        readme: Option<StringOrBool>,
+        keywords: Option<Vec<String>>,
+        categories: Option<Vec<String>>,
+        license: Option<String>,
+        license_file: Option<String>,
+        repository: Option<String>,
+        publish: Option<VecStringOrBool>,
+        edition: Option<String>,
+        badges: Option<BTreeMap<String, BTreeMap<String, String>>>,
+    ) -> InheritableFields {
+        Self {
+            dependencies,
+            version,
+            authors,
+            description,
+            homepage,
+            documentation,
+            readme,
+            keywords,
+            categories,
+            license,
+            license_file,
+            repository,
+            publish,
+            edition,
+            badges,
+        }
+    }
+
+    pub fn dependencies(&self) -> Option<BTreeMap<String, TomlDependency>> {
+        self.dependencies.clone()
+    }
+
+    pub fn version(&self) -> Option<semver::Version> {
+        self.version.clone()
+    }
+
+    pub fn authors(&self) -> Option<Vec<String>> {
+        self.authors.clone()
+    }
+
+    pub fn description(&self) -> Option<String> {
+        self.description.clone()
+    }
+
+    pub fn homepage(&self) -> Option<String> {
+        self.homepage.clone()
+    }
+
+    pub fn documentation(&self) -> Option<String> {
+        self.documentation.clone()
+    }
+
+    pub fn readme(&self) -> Option<StringOrBool> {
+        self.readme.clone()
+    }
+
+    pub fn keywords(&self) -> Option<Vec<String>> {
+        self.keywords.clone()
+    }
+
+    pub fn categories(&self) -> Option<Vec<String>> {
+        self.categories.clone()
+    }
+
+    pub fn license(&self) -> Option<String> {
+        self.license.clone()
+    }
+
+    pub fn license_file(&self) -> Option<String> {
+        self.license_file.clone()
+    }
+
+    pub fn repository(&self) -> Option<String> {
+        self.repository.clone()
+    }
+
+    pub fn publish(&self) -> Option<VecStringOrBool> {
+        self.publish.clone()
+    }
+
+    pub fn edition(&self) -> Option<String> {
+        self.edition.clone()
+    }
+
+    pub fn badges(&self) -> Option<BTreeMap<String, BTreeMap<String, String>>> {
+        self.badges.clone()
+    }
+}

src/doc/src/reference/unstable.md

@@ -68,6 +68,7 @@ Each new feature described below should explain how to use it.
     * [avoid-dev-deps](#avoid-dev-deps) — Prevents the resolver from including dev-dependencies during resolution.
     * [minimal-versions](#minimal-versions) — Forces the resolver to use the lowest compatible version instead of the highest.
     * [public-dependency](#public-dependency) — Allows dependencies to be classified as either public or private.
+    * [workspace-inheritance](#workspace-inheritance) - Allow workspace members to share fields and dependencies
 * Output behavior
     * [out-dir](#out-dir) — Adds a directory where artifacts are copied to.
     * [terminal-width](#terminal-width) — Tells rustc the width of the terminal so that long diagnostic messages can be truncated to be more readable.
@@ -1342,3 +1343,65 @@ See the [Features chapter](features.md#dependency-features) for more information
 The `-Ztimings` option has been stabilized as `--timings` in the 1.60 release.
 (`--timings=html` and the machine-readable `--timings=json` output remain
 unstable and require `-Zunstable-options`.)
+
+### workspace-inheritance
+
+* RFC: [#2906](https://github.com/rust-lang/rfcs/blob/master/text/2906-cargo-workspace-deduplicate.md)
+* Tracking Issue: [#8415](https://github.com/rust-lang/cargo/issues/8415)
+
+The `workspace-inheritance` feature allows workspace members to inherit fields
+and dependencies from a workspace.
+
+Example 1: 
+
+```toml
+# in workspace's Cargo.toml
+[workspace.dependencies]
+log = "0.3.1"
+log2 = { version = "2.0.0", package = "log" }
+serde = { git = 'https://github.com/serde-rs/serde' }
+wasm-bindgen-cli = { path = "crates/cli" }
+```
+
+```toml
+# in a workspace member's Cargo.toml
+[dependencies]
+log = { workspace = true }
+log2 = { workspace = true }
+```
+
+Example 2: 
+```toml
+# in workspace's Cargo.toml
+[workspace]
+version = "1.2.3"
+authors = ["Nice Folks"]
+description = "..."
+documentation = "https://example.github.io/example"
+readme = "README.md"
+homepage = "https://example.com"
+repository = "https://github.com/example/example"
+license = "MIT"
+license-file = "./LICENSE"
+keywords = ["cli"]
+categories = ["development-tools"]
+publish = false
+edition = "2018"
+```
+
+```toml
+# in a workspace member's Cargo.toml
+[package]
+version = { workspace = true }
+authors = { workspace = true }
+description = { workspace = true }
+documentation = { workspace = true }
+readme = { workspace = true }
+homepage = { workspace = true }
+repository = { workspace = true }
+license = { workspace = true }
+license-file = { workspace = true }
+keywords = { workspace = true }
+categories = { workspace = true }
+publish = { workspace = true }
+```

tests/testsuite/deduplicate_workspace.rs

@@ -0,0 +1,817 @@
+//! Tests for deduplicating Cargo.toml fields with { workspace = true }
+use cargo_test_support::registry::{Dependency, Package};
+use cargo_test_support::{basic_lib_manifest, git, paths, project, publish, registry};
+
+#[cargo_test]
+fn permit_additional_workspace_fields() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [workspace]
+            members = ["bar"]
+            version = "1.2.3"
+            authors = ["Rustaceans"]
+            description = "This is a crate"
+            documentation = "https://www.rust-lang.org/learn"
+            readme = "README.md"
+            homepage = "https://www.rust-lang.org"
+            repository = "https://github.com/example/example"
+            license = "MIT"
+            license-file = "LICENSE"
+            keywords = ["cli"]
+            categories = ["development-tools"]
+            publish = false
+            edition = "2018"
+
+            [workspace.badges]
+            gitlab = { repository = "https://gitlab.com/rust-lang/rust", branch = "master" }
+
+            [workspace.dependencies]
+            dep = "0.1"
+        "#,
+        )
+        .file(
+            "bar/Cargo.toml",
+            r#"
+              [package]
+              name = "bar"
+              version = "0.1.0"
+              authors = []
+              workspace = ".."
+              "#,
+        )
+        .file("bar/src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build")
+        // Should not warn about unused fields.
+        .with_stderr(
+            "\
+[COMPILING] bar v0.1.0 ([CWD]/bar)
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+        )
+        .run();
+
+    p.cargo("check").run();
+    let lockfile = p.read_lockfile();
+    assert!(!lockfile.contains("dep"));
+}
+
+#[cargo_test]
+fn deny_optional_dependencies() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            cargo-features = ["workspace-inheritance"]
+
+            [workspace]
+            members = ["bar"]
+
+            [workspace.dependencies]
+            dep1 = { version = "0.1", optional = true }
+        "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .file(
+            "bar/Cargo.toml",
+            r#"
+              [package]
+              name = "bar"
+              version = "0.1.0"
+              authors = []
+              workspace = ".."
+              "#,
+        )
+        .file("bar/src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build")
+        .with_status(101)
+        .with_stderr(
+            "\
+[ERROR] failed to parse manifest at `[..]foo/Cargo.toml`
+
+Caused by:
+  dep1 is optional, but workspace dependencies cannot be optional
+",
+        )
+        .masquerade_as_nightly_cargo()
+        .run();
+}
+
+#[cargo_test]
+fn inherit_own_workspace_fields() {
+    registry::init();
+
+    let p = project().build();
+
+    let _ = git::repo(&paths::root().join("foo"))
+        .file(
+            "Cargo.toml",
+            r#"
+            cargo-features = ["workspace-inheritance"]
+            badges = { workspace = true }
+
+            [package]
+            name = "foo"
+            version = { workspace = true }
+            authors = { workspace = true }
+            description = { workspace = true }
+            documentation = { workspace = true }
+            readme = { workspace = true }
+            homepage = { workspace = true }
+            repository = { workspace = true }
+            license = { workspace = true }
+            license-file = { workspace = true }
+            keywords = { workspace = true }
+            categories = { workspace = true }
+            publish = { workspace = true }
+            edition = { workspace = true }
+
+            [workspace]
+            members = []
+            version = "1.2.3"
+            authors = ["Rustaceans"]
+            description = "This is a crate"
+            documentation = "https://www.rust-lang.org/learn"
+            readme = "README.md"
+            homepage = "https://www.rust-lang.org"
+            repository = "https://github.com/example/example"
+            license = "MIT"
+            license-file = "LICENSE"
+            keywords = ["cli"]
+            categories = ["development-tools"]
+            publish = true
+            edition = "2018"
+            [workspace.badges]
+            gitlab = { repository = "https://gitlab.com/rust-lang/rust", branch = "master" }
+            "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .file("LICENSE", "license")
+        .file("README.md", "README.md")
+        .build();
+
+    p.cargo("publish --token sekrit")
+        .masquerade_as_nightly_cargo()
+        .run();
+    publish::validate_upload_with_contents(
+        r#"
+        {
+          "authors": ["Rustaceans"],
+          "badges": {
+            "gitlab": { "branch": "master", "repository": "https://gitlab.com/rust-lang/rust" }
+          },
+          "categories": ["development-tools"],
+          "deps": [],
+          "description": "This is a crate",
+          "documentation": "https://www.rust-lang.org/learn",
+          "features": {},
+          "homepage": "https://www.rust-lang.org",
+          "keywords": ["cli"],
+          "license": "MIT",
+          "license_file": "LICENSE",
+          "links": null,
+          "name": "foo",
+          "readme": "README.md",
+          "readme_file": "README.md",
+          "repository": "https://github.com/example/example",
+          "vers": "1.2.3"
+          }
+        "#,
+        "foo-1.2.3.crate",
+        &[
+            "Cargo.lock",
+            "Cargo.toml",
+            "Cargo.toml.orig",
+            "src/main.rs",
+            "README.md",
+            "LICENSE",
+            ".cargo_vcs_info.json",
+        ],
+        &[(
+            "Cargo.toml",
+            &format!(
+                r#"{}
+cargo-features = ["workspace-inheritance"]
+
+[package]
+edition = "2018"
+name = "foo"
+version = "1.2.3"
+authors = ["Rustaceans"]
+publish = true
+description = "This is a crate"
+homepage = "https://www.rust-lang.org"
+documentation = "https://www.rust-lang.org/learn"
+readme = "README.md"
+keywords = ["cli"]
+categories = ["development-tools"]
+license = "MIT"
+license-file = "LICENSE"
+repository = "https://github.com/example/example"
+
+[badges.gitlab]
+branch = "master"
+repository = "https://gitlab.com/rust-lang/rust"
+"#,
+                cargo::core::package::MANIFEST_PREAMBLE
+            ),
+        )],
+    );
+}
+
+#[cargo_test]
+fn inherit_own_dependencies() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            cargo-features = ["workspace-inheritance"]
+
+            [project]
+            name = "bar"
+            version = "0.2.0"
+            authors = []
+
+            [dependencies]
+            dep = { workspace = true }
+
+            [build-dependencies]
+            dep-build = { workspace = true }
+
+            [dev-dependencies]
+            dep-dev = { workspace = true }
+
+            [workspace]
+            members = []
+
+            [workspace.dependencies]
+            dep = "0.1"
+            dep-build = "0.8"
+            dep-dev = "0.5.2"
+        "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    Package::new("dep", "0.1.2").publish();
+    Package::new("dep-build", "0.8.2").publish();
+    Package::new("dep-dev", "0.5.2").publish();
+
+    p.cargo("build")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[UPDATING] `[..]` index
+[DOWNLOADING] crates ...
+[DOWNLOADED] dep-build v0.8.2 ([..])
+[DOWNLOADED] dep v0.1.2 ([..])
+[COMPILING] dep v0.1.2
+[COMPILING] bar v0.2.0 ([CWD])
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+        )
+        .run();
+
+    p.cargo("check").masquerade_as_nightly_cargo().run();
+    let lockfile = p.read_lockfile();
+    assert!(lockfile.contains("dep"));
+    assert!(lockfile.contains("dep-dev"));
+    assert!(lockfile.contains("dep-build"));
+    p.cargo("publish --token sekrit")
+        .masquerade_as_nightly_cargo()
+        .run();
+    publish::validate_upload_with_contents(
+        r#"
+        {
+          "authors": [],
+          "badges": {},
+          "categories": [],
+          "deps": [
+            {
+              "default_features": true,
+              "features": [],
+              "kind": "normal",
+              "name": "dep",
+              "optional": false,
+              "registry": "https://github.com/rust-lang/crates.io-index",
+              "target": null,
+              "version_req": "^0.1"
+            },
+            {
+              "default_features": true,
+              "features": [],
+              "kind": "dev",
+              "name": "dep-dev",
+              "optional": false,
+              "registry": "https://github.com/rust-lang/crates.io-index",
+              "target": null,
+              "version_req": "^0.5.2"
+            },
+            {
+              "default_features": true,
+              "features": [],
+              "kind": "build",
+              "name": "dep-build",
+              "optional": false,
+              "registry": "https://github.com/rust-lang/crates.io-index",
+              "target": null,
+              "version_req": "^0.8"
+            }
+          ],
+          "description": null,
+          "documentation": null,
+          "features": {},
+          "homepage": null,
+          "keywords": [],
+          "license": null,
+          "license_file": null,
+          "links": null,
+          "name": "bar",
+          "readme": null,
+          "readme_file": null,
+          "repository": null,
+          "vers": "0.2.0"
+          }
+        "#,
+        "bar-0.2.0.crate",
+        &["Cargo.toml", "Cargo.toml.orig", "Cargo.lock", "src/main.rs"],
+        &[(
+            "Cargo.toml",
+            &format!(
+                r#"{}
+cargo-features = ["workspace-inheritance"]
+
+[package]
+name = "bar"
+version = "0.2.0"
+authors = []
+
+[dependencies.dep]
+version = "0.1"
+
+[dev-dependencies.dep-dev]
+version = "0.5.2"
+
+[build-dependencies.dep-build]
+version = "0.8"
+"#,
+                cargo::core::package::MANIFEST_PREAMBLE
+            ),
+        )],
+    );
+}
+
+#[cargo_test]
+fn inherit_own_detailed_dependencies() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            cargo-features = ["workspace-inheritance"]
+
+            [project]
+            name = "bar"
+            version = "0.2.0"
+            authors = []
+
+            [dependencies]
+            dep = { workspace = true }
+
+            [workspace]
+            members = []
+
+            [workspace.dependencies]
+            dep = { version = "0.1.2", features = ["testing"] }
+        "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    Package::new("dep", "0.1.2")
+        .feature("testing", &vec![])
+        .publish();
+
+    p.cargo("build")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[UPDATING] `[..]` index
+[DOWNLOADING] crates ...
+[DOWNLOADED] dep v0.1.2 ([..])
+[COMPILING] dep v0.1.2
+[COMPILING] bar v0.2.0 ([CWD])
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+        )
+        .run();
+
+    p.cargo("check").masquerade_as_nightly_cargo().run();
+    let lockfile = p.read_lockfile();
+    assert!(lockfile.contains("dep"));
+    p.cargo("publish --token sekrit")
+        .masquerade_as_nightly_cargo()
+        .run();
+    publish::validate_upload_with_contents(
+        r#"
+        {
+          "authors": [],
+          "badges": {},
+          "categories": [],
+          "deps": [
+            {
+              "default_features": true,
+              "features": ["testing"],
+              "kind": "normal",
+              "name": "dep",
+              "optional": false,
+              "registry": "https://github.com/rust-lang/crates.io-index",
+              "target": null,
+              "version_req": "^0.1.2"
+            }
+          ],
+          "description": null,
+          "documentation": null,
+          "features": {},
+          "homepage": null,
+          "keywords": [],
+          "license": null,
+          "license_file": null,
+          "links": null,
+          "name": "bar",
+          "readme": null,
+          "readme_file": null,
+          "repository": null,
+          "vers": "0.2.0"
+          }
+        "#,
+        "bar-0.2.0.crate",
+        &["Cargo.toml", "Cargo.toml.orig", "Cargo.lock", "src/main.rs"],
+        &[(
+            "Cargo.toml",
+            &format!(
+                r#"{}
+cargo-features = ["workspace-inheritance"]
+
+[package]
+name = "bar"
+version = "0.2.0"
+authors = []
+
+[dependencies.dep]
+version = "0.1.2"
+features = ["testing"]
+"#,
+                cargo::core::package::MANIFEST_PREAMBLE
+            ),
+        )],
+    );
+}
+
+#[cargo_test]
+fn inherit_from_own_undefined_field() {
+    registry::init();
+
+    let p = project().build();
+
+    let _ = git::repo(&paths::root().join("foo"))
+        .file(
+            "Cargo.toml",
+            r#"
+            cargo-features = ["workspace-inheritance"]
+
+            [package]
+            name = "foo"
+            version = "1.2.5"
+            authors = ["rustaceans"]
+            description = { workspace = true }
+
+            [workspace]
+            members = []
+            "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build")
+        .masquerade_as_nightly_cargo()
+        .with_status(101)
+        .with_stderr(
+            "\
+[ERROR] failed to parse manifest at `[CWD]/Cargo.toml`
+
+Caused by:
+  error reading `description` from workspace root manifest's `[workspace.description]`
+",
+        )
+        .run();
+}
+
+#[cargo_test]
+fn inherited_dependencies_union_features() {
+    Package::new("dep", "0.1.0")
+        .feature("fancy", &["fancy_dep"])
+        .feature("dancy", &["dancy_dep"])
+        .add_dep(Dependency::new("fancy_dep", "0.2").optional(true))
+        .add_dep(Dependency::new("dancy_dep", "0.6").optional(true))
+        .file("src/lib.rs", "")
+        .publish();
+
+    Package::new("fancy_dep", "0.2.4").publish();
+    Package::new("dancy_dep", "0.6.8").publish();
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            cargo-features = ["workspace-inheritance"]
+
+            [project]
+            name = "bar"
+            version = "0.2.0"
+            authors = []
+            [dependencies]
+            dep = { workspace = true, features = ["dancy"] }
+
+            [workspace]
+            members = []
+            [workspace.dependencies]
+            dep = { version = "0.1", features = ["fancy"] }
+        "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "\
+[UPDATING] `[..]` index
+[DOWNLOADING] crates ...
+[DOWNLOADED] fancy_dep v0.2.4 ([..])
+[DOWNLOADED] dep v0.1.0 ([..])
+[DOWNLOADED] dancy_dep v0.6.8 ([..])
+[COMPILING] [..]
+[COMPILING] [..]
+[COMPILING] dep v0.1.0
+[COMPILING] bar v0.2.0 ([CWD])
+[FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
+",
+        )
+        .run();
+
+    let lockfile = p.read_lockfile();
+    assert!(lockfile.contains("dep"));
+    assert!(lockfile.contains("fancy_dep"));
+    assert!(lockfile.contains("dancy_dep"));
+}
+
+#[cargo_test]
+fn deny_inherit_fields_from_parent_workspace() {
+    registry::init();
+
+    let p = project().build();
+
+    let _ = git::repo(&paths::root().join("foo"))
+        .file(
+            "Cargo.toml",
+            r#"
+            [workspace]
+            members = ["bar"]
+            version = "1.2.3"
+            "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .file(
+            "bar/Cargo.toml",
+            r#"
+            cargo-features = ["workspace-inheritance"]
+
+            [package]
+            name = "bar"
+            workspace = ".."
+            version = { workspace = true }
+        "#,
+        )
+        .file("LICENSE", "license")
+        .file("README.md", "README.md")
+        .file("bar/src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build")
+        .masquerade_as_nightly_cargo()
+        .cwd("bar")
+        .with_status(101)
+        .with_stderr(
+            "\
+[ERROR] failed to parse manifest at `[CWD]/Cargo.toml`
+
+Caused by:
+  You cannot inherit fields from a parent workspace currently, tried to on version
+",
+        )
+        .run();
+}
+
+#[cargo_test]
+fn deny_inherit_dependencies_from_parent_workspace() {
+    let git_project = git::new("detailed", |project| {
+        project
+            .file("Cargo.toml", &basic_lib_manifest("detailed"))
+            .file(
+                "src/detailed.rs",
+                r#"
+                pub fn hello() -> &'static str {
+                    "hello world"
+                }
+            "#,
+            )
+    });
+
+    // Make a new branch based on the current HEAD commit
+    let repo = git2::Repository::open(&git_project.root()).unwrap();
+    let head = repo.head().unwrap().target().unwrap();
+    let head = repo.find_commit(head).unwrap();
+    repo.branch("branchy", &head, true).unwrap();
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            &format!(
+                r#"
+            [workspace]
+            members = ["bar"]
+
+            [workspace.dependencies]
+            detailed = {{ git = '{}', branch = "branchy" }}
+        "#,
+                git_project.url()
+            ),
+        )
+        .file(
+            "bar/Cargo.toml",
+            r#"
+            cargo-features = ["workspace-inheritance"]
+
+            [project]
+            workspace = ".."
+            name = "bar"
+            version = "0.2.0"
+            authors = []
+
+            [dependencies]
+            detailed = { workspace = true }
+        "#,
+        )
+        .file("bar/src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build")
+        .masquerade_as_nightly_cargo()
+        .with_status(101)
+        .with_stderr(
+            "\
+[ERROR] failed to load manifest for workspace member `[CWD]/bar`
+
+Caused by:
+  failed to parse manifest at `[CWD]/bar/Cargo.toml`
+
+Caused by:
+  You cannot inherit fields from a parent workspace currently, tried to on `[dependency.detailed]`
+",
+        )
+        .run();
+}
+
+#[cargo_test]
+fn error_workspace_false() {
+    registry::init();
+
+    let p = project().build();
+
+    let _ = git::repo(&paths::root().join("foo"))
+        .file(
+            "Cargo.toml",
+            r#"
+            [workspace]
+            members = ["bar"]
+            "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .file(
+            "bar/Cargo.toml",
+            r#"
+            [package]
+            name = "bar"
+            workspace = ".."
+            version = "1.2.3"
+            authors = ["rustaceans"]
+            description = { workspace = false }
+        "#,
+        )
+        .file("bar/src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build")
+        .cwd("bar")
+        .with_status(101)
+        .with_stderr(
+            "\
+[ERROR] failed to parse manifest at `[CWD]/Cargo.toml`
+
+Caused by:
+  workspace cannot be false for key `package.description`
+",
+        )
+        .run();
+}
+
+#[cargo_test]
+fn workspace_inheritance_not_enabled() {
+    registry::init();
+
+    let p = project().build();
+
+    let _ = git::repo(&paths::root().join("foo"))
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+            name = "foo"
+            version = "1.2.5"
+            authors = ["rustaceans"]
+            description = { workspace = true }
+
+            [workspace]
+            members = []
+            "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build")
+        .masquerade_as_nightly_cargo()
+        .with_status(101)
+        .with_stderr(
+            "\
+[ERROR] failed to parse manifest at `[CWD]/Cargo.toml`
+
+Caused by:
+  feature `workspace-inheritance` is required
+
+  The package requires the Cargo feature called `workspace-inheritance`, \
+  but that feature is not stabilized in this version of Cargo (1.[..]).
+  Consider adding `cargo-features = [\"workspace-inheritance\"]` to the top of Cargo.toml \
+  (above the [package] table) to tell Cargo you are opting in to use this unstable feature.
+  See https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#workspace-inheritance \
+  for more information about the status of this feature.
+",
+        )
+        .run();
+}
+
+#[cargo_test]
+fn nightly_required() {
+    registry::init();
+
+    let p = project().build();
+
+    let _ = git::repo(&paths::root().join("foo"))
+        .file(
+            "Cargo.toml",
+            r#"
+            cargo-features = ["workspace-inheritance"]
+
+            [package]
+            name = "foo"
+            version = "1.2.5"
+            authors = ["rustaceans"]
+            description = { workspace = true }
+
+            [workspace]
+            members = []
+            "#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .build();
+
+    p.cargo("build")
+        .with_status(101)
+        .with_stderr(
+            "\
+[ERROR] failed to parse manifest at `[CWD]/Cargo.toml`
+
+Caused by:
+  the cargo feature `workspace-inheritance` requires a nightly version of Cargo, \
+  but this is the `stable` channel
+  See [..]
+  See https://doc.rust-lang.org/[..]cargo/reference/unstable.html#workspace-inheritance \
+  for more information about using this feature.
+",
+        )
+        .run();
+}

tests/testsuite/main.rs

@@ -39,6 +39,7 @@ mod cross_compile;
 mod cross_publish;
 mod custom_target;
 mod death;
+mod deduplicate_workspace;
 mod dep_info;
 mod directory;
 mod doc;