Fix issue-11010

Author: LuuuXXX

src/cargo/ops/cargo_add/mod.rs

@@ -7,6 +7,7 @@ use std::collections::BTreeSet;
 use std::collections::VecDeque;
 use std::fmt::Write;
 use std::path::Path;
+use std::str::FromStr;
 
 use anyhow::Context as _;
 use cargo_util::paths;
@@ -196,6 +197,13 @@ pub fn add(workspace: &Workspace<'_>, options: &AddOptions<'_>) -> CargoResult<(
         print_dep_table_msg(&mut options.config.shell(), &dep)?;
 
         manifest.insert_into_table(&dep_table, &dep)?;
+        if dep.optional == Some(true) {
+            let is_namespaced_features_supported =
+                check_rust_version_for_optional_dependency(options.spec.rust_version())?;
+            if is_namespaced_features_supported {
+                manifest.explicit_activate_optional_dependency_as_feature(&dep)?;
+            }
+        }
         manifest.gc_dep(dep.toml_key());
     }
 
@@ -469,6 +477,26 @@ fn check_invalid_ws_keys(toml_key: &str, arg: &DepOp) -> CargoResult<()> {
     Ok(())
 }
 
+/// When the `--optional` option is added using `cargo add`, we need to
+/// check the current rust-version. As the `dep:` syntax is only avaliable
+/// starting with Rust 1.60.0
+///
+/// `true` means that the rust-version is None or the rust-version is higher
+/// than the version needed.
+///
+/// Note: Previous versions can only use the implicit feature name.
+fn check_rust_version_for_optional_dependency(
+    rust_version: Option<&RustVersion>,
+) -> CargoResult<bool> {
+    match rust_version {
+        Some(version) => {
+            let syntax_support_version = RustVersion::from_str("1.60.0")?;
+            Ok(&syntax_support_version <= version)
+        }
+        None => Ok(true),
+    }
+}
+
 /// Provide the existing dependency for the target table
 ///
 /// If it doesn't exist but exists in another table, let's use that as most likely users

src/cargo/util/toml_mut/manifest.rs

@@ -363,6 +363,23 @@ impl LocalManifest {
         Ok(())
     }
 
+    /// Add feature entry to a Cargo.toml.
+    pub fn explicit_activate_optional_dependency_as_feature(
+        &mut self,
+        dep: &Dependency,
+    ) -> CargoResult<()> {
+        let dep_key = dep.toml_key();
+        // Check whether `dep:<dep>` is defined in the [features] section.
+        if !self.is_explicit_dep_activation(dep_key) {
+            let table = self.get_table_mut(&vec![String::from("features")])?;
+            let dep_name = dep.rename.as_deref().unwrap_or(&dep.name);
+            let new_feature: toml_edit::Value = [format!("dep:{dep_name}")].iter().collect();
+            table[dep_key] = toml_edit::value(new_feature);
+        }
+
+        Ok(())
+    }
+
     /// Remove entry from a Cargo.toml.
     pub fn remove_from_table(&mut self, table_path: &[String], name: &str) -> CargoResult<()> {
         let parent_table = self.get_table_mut(table_path)?;

tests/testsuite/cargo_add/change_rename_target/out/Cargo.toml

@@ -6,3 +6,6 @@ version = "0.0.0"
 
 [dependencies]
 some-package = { package = "my-package2", version = "99999.0.0", optional = true }
+
+[features]
+some-package = ["dep:some-package"]

tests/testsuite/cargo_add/detect_workspace_inherit_optional/out/primary/Cargo.toml

@@ -4,3 +4,6 @@ version = "0.0.0"
 
 [dependencies]
 foo = { workspace = true, optional = true }
+
+[features]
+foo = ["dep:foo"]

tests/testsuite/cargo_add/optional/out/Cargo.toml

@@ -7,3 +7,7 @@ version = "0.0.0"
 [dependencies]
 my-package1 = { version = "99999.0.0", optional = true }
 my-package2 = { version = "0.4.1", optional = true }
+
+[features]
+my-package1 = ["dep:my-package1"]
+my-package2 = ["dep:my-package2"]

tests/testsuite/cargo_add/overwrite_git_with_path/out/primary/Cargo.toml

@@ -6,3 +6,6 @@ version = "0.0.0"
 
 [dependencies]
 cargo-list-test-fixture-dependency = { optional = true, path = "../dependency", version = "0.0.0" }
+
+[features]
+cargo-list-test-fixture-dependency = ["dep:cargo-list-test-fixture-dependency"]

tests/testsuite/cargo_add/overwrite_inherit_optional_noop/out/primary/Cargo.toml

@@ -4,3 +4,6 @@ version = "0.0.0"
 
 [dependencies]
 foo = { workspace = true, optional = true }
+
+[features]
+foo = ["dep:foo"]

tests/testsuite/cargo_add/overwrite_name_noop/out/Cargo.toml

@@ -7,3 +7,6 @@ version = "0.0.0"
 
 [dependencies]
 your-face = { version = "0.0.0", path = "dependency", optional = true, default-features = false, features = ["nose", "mouth"], registry = "alternative" }
+
+[features]
+your-face = ["dep:your-face"]

tests/testsuite/cargo_add/overwrite_no_optional_with_optional/out/Cargo.toml

@@ -7,3 +7,7 @@ version = "0.0.0"
 [dependencies]
 my-package1 = { version = "99999.0.0", optional = true }
 my-package2 = { version = "0.4.1", optional = true }
+
+[features]
+my-package1 = ["dep:my-package1"]
+my-package2 = ["dep:my-package2"]

tests/testsuite/cargo_add/overwrite_optional/out/Cargo.toml

@@ -7,3 +7,7 @@ version = "0.0.0"
 [dependencies]
 my-package1 = { version = "99999.0.0", optional = true }
 my-package2 = { version = "0.4.1", optional = true }
+
+[features]
+my-package1 = ["dep:my-package1"]
+my-package2 = ["dep:my-package2"]