Fix issue-11010

Author: LuuuXXX

src/cargo/ops/cargo_add/mod.rs

@@ -196,6 +196,14 @@ 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 let Some(option) = dep.optional {
+            let rust_version_check =
+                check_rust_version_for_optional_dependency(workspace.rust_version())?;
+            if option && rust_version_check {
+                let features_table: Vec<String> = vec![String::from("features")];
+                manifest.insert_into_feature_table(&features_table, &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 = String::from("1.60.0");
+            Ok(version.to_string().cmp(&syntax_support_version).is_ge())
+        }
+        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/dependency.rs

@@ -583,6 +583,13 @@ impl Dependency {
             unreachable!("Invalid dependency type: {}", item.type_name());
         }
     }
+
+    /// Convert dependency to Feature.
+    pub fn to_feature(&self) -> Feature {
+        let feature = Feature::new(self.name.to_string(), self.rename.to_owned());
+        let feature_value = feature.as_feature();
+        feature.add_feature(feature_value)
+    }
 }
 
 fn overwrite_value(
@@ -921,6 +928,76 @@ impl Display for WorkspaceSource {
     }
 }
 
+pub struct Feature {
+    /// The name of the feature (as it is set in its `Cargo.toml`).
+    pub name: String,
+    /// List of features to add.
+    pub features: IndexSet<String>,
+    /// this is the new name for the dependency
+    /// as a string.  None if it is not renamed.
+    pub rename: Option<String>,
+}
+
+impl Feature {
+    pub fn new(name: String, rename: Option<String>) -> Self {
+        Self {
+            name: name,
+            features: IndexSet::new(),
+            rename: rename,
+        }
+    }
+
+    pub fn add_feature(mut self, value: String) -> Self {
+        self.features.insert(value);
+        self
+    }
+
+    pub fn as_feature(&self) -> String {
+        if let Some(rename) = &self.rename {
+            format!("dep:{}", rename)
+        } else {
+            format!("dep:{}", self.name)
+        }
+    }
+
+    /// Convert feature to TOML.
+    /// Panics if the path is relative
+    pub fn to_toml(&self, crate_root: &Path) -> toml_edit::Item {
+        assert!(
+            crate_root.is_absolute(),
+            "Absolute path needed, got: {}",
+            crate_root.display()
+        );
+        let features: toml_edit::Value = self.features.iter().cloned().collect();
+        toml_edit::value(features)
+    }
+
+    /// Check whether `dep:<dep>` is defined in the features section.
+    ///
+    /// `true`  if there is a define `dep:<dep>`
+    /// `false` if `dep:<dep>` is not used ever.
+    ///
+    /// Make sure that `dep:<dep>` is included in one of features in the features table.
+    pub fn check_duplicate_feature(&self, item: &mut toml_edit::Item) -> bool {
+        item.as_table_like_mut().unwrap().iter().any(|(_, values)| {
+            if let Some(values) = &values.as_array() {
+                values.iter().any(|value| match value.as_str() {
+                    Some(val) => val.to_string().eq(&self.as_feature()),
+                    None => false,
+                })
+            } else {
+                false
+            }
+        })
+    }
+}
+
+impl std::fmt::Display for Feature {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        self.name.fmt(f)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use std::path::Path;

src/cargo/util/toml_mut/manifest.rs

@@ -363,6 +363,30 @@ impl LocalManifest {
         Ok(())
     }
 
+    /// Add feature entry to a Cargo.toml.
+    pub fn insert_into_feature_table(
+        &mut self,
+        table_path: &[String],
+        dep: &Dependency,
+    ) -> CargoResult<()> {
+        let crate_root = self
+            .path
+            .parent()
+            .expect("manifest path is absolute")
+            .to_owned();
+        let dep_key = dep.toml_key();
+        let feature = dep.to_feature();
+        let table = self.get_table_mut(table_path)?;
+
+        // Check whether `dep:<dep>` is defined in the [features] section.
+        if !feature.check_duplicate_feature(table) {
+            let new_feature = feature.to_toml(&crate_root);
+            table[dep_key] = 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"]