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 +197,14 @@ 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.current().unwrap().rust_version(),
+            )?;
+            if option && rust_version_check {
+                manifest.insert_into_feature_table(&dep)?;
+            }
+        }
         manifest.gc_dep(dep.toml_key());
     }
 
@@ -469,6 +478,26 @@ 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(version.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

@@ -921,6 +921,47 @@ impl Display for WorkspaceSource {
     }
 }
 
+impl Dependency {
+    /// Convert denpency as feature to TOML.
+    /// Panics if the path is relative
+    pub fn to_toml_as_feature(&self, crate_root: &Path) -> toml_edit::Item {
+        assert!(
+            crate_root.is_absolute(),
+            "Absolute path needed, got: {}",
+            crate_root.display()
+        );
+        let features: toml_edit::Value = vec![self.as_feature()].iter().collect();
+        toml_edit::value(features)
+    }
+
+    pub fn as_feature(&self) -> String {
+        if let Some(rename) = &self.rename {
+            format!("dep:{}", rename)
+        } else {
+            format!("dep:{}", self.name)
+        }
+    }
+
+    /// 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 is_active_as_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
+            }
+        })
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use std::path::Path;

src/cargo/util/toml_mut/manifest.rs

@@ -363,6 +363,25 @@ impl LocalManifest {
         Ok(())
     }
 
+    /// Add feature entry to a Cargo.toml.
+    pub fn insert_into_feature_table(&mut self, dep: &Dependency) -> CargoResult<()> {
+        let crate_root = self
+            .path
+            .parent()
+            .expect("manifest path is absolute")
+            .to_owned();
+        let dep_key = dep.toml_key();
+        let table = self.get_table_mut(&vec![String::from("features")])?;
+
+        // Check whether `dep:<dep>` is defined in the [features] section.
+        if !dep.is_active_as_feature(table) {
+            let new_feature = dep.to_toml_as_feature(&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"]