Implement base paths (RFC 3529) 1/n: path dep and patch support

CHANGELOG.md

@@ -4,6 +4,10 @@
 [a2b58c3d...HEAD](https://github.com/rust-lang/cargo/compare/a2b58c3d...HEAD)
 
 ### Added
+- Added the `path-bases` feature to support paths that resolve relatively to a
+  base specified in the config.
+  [docs](https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#path-bases)
+  [#14360](https://github.com/rust-lang/cargo/pull/14360)
 
 ### Changed
 

crates/cargo-util-schemas/src/manifest/mod.rs

@@ -776,6 +776,7 @@ pub struct TomlDetailedDependency<P: Clone = String> {
     // `path` is relative to the file it appears in. If that's a `Cargo.toml`, it'll be relative to
     // that TOML file, and if it's a `.cargo/config` file, it'll be relative to that file.
     pub path: Option<P>,
+    pub base: Option<PathBaseName>,
     pub git: Option<String>,
     pub branch: Option<String>,
     pub tag: Option<String>,
@@ -815,6 +816,7 @@ impl<P: Clone> Default for TomlDetailedDependency<P> {
             registry: Default::default(),
             registry_index: Default::default(),
             path: Default::default(),
+            base: Default::default(),
             git: Default::default(),
             branch: Default::default(),
             tag: Default::default(),
@@ -1413,6 +1415,16 @@ impl<T: AsRef<str>> FeatureName<T> {
     }
 }
 
+str_newtype!(PathBaseName);
+
+impl<T: AsRef<str>> PathBaseName<T> {
+    /// Validated path base name
+    pub fn new(name: T) -> Result<Self, NameValidationError> {
+        restricted_names::validate_path_base_name(name.as_ref())?;
+        Ok(Self(name))
+    }
+}
+
 /// Corresponds to a `target` entry, but `TomlTarget` is already used.
 #[derive(Serialize, Deserialize, Debug, Clone)]
 #[serde(rename_all = "kebab-case")]

crates/cargo-util-schemas/src/restricted_names.rs

@@ -238,6 +238,37 @@ pub(crate) fn validate_feature_name(name: &str) -> Result<()> {
     Ok(())
 }
 
+pub(crate) fn validate_path_base_name(name: &str) -> Result<()> {
+    let what = "path base name";
+    let mut chars = name.chars();
+
+    let Some(first_char) = chars.next() else {
+        return Err(ErrorKind::Empty(what).into());
+    };
+
+    if !first_char.is_alphabetic() {
+        return Err(ErrorKind::InvalidCharacter {
+            ch: first_char,
+            what,
+            name: name.into(),
+            reason: "first character must be a letter",
+        }
+        .into());
+    }
+
+    if let Some(ch) = chars.find(|c| !c.is_alphanumeric() && *c != '_' && *c != '-') {
+        return Err(ErrorKind::InvalidCharacter {
+            ch,
+            what,
+            name: name.into(),
+            reason: "allowed characters are letters, numbers, underscore, and hyphen",
+        }
+        .into());
+    }
+
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -264,4 +295,15 @@ mod tests {
         assert!(validate_feature_name("a¼").is_err());
         assert!(validate_feature_name("").is_err());
     }
+
+    #[test]
+    fn validate_path_base_names() {
+        assert!(validate_path_base_name("foo").is_ok());
+        assert!(validate_path_base_name("foo12342_42-hello").is_ok());
+
+        assert!(validate_path_base_name("").is_err());
+        assert!(validate_path_base_name("42foo").is_err());
+        assert!(validate_path_base_name("_foo").is_err());
+        assert!(validate_path_base_name("foo+bar").is_err());
+    }
 }

src/cargo/core/features.rs

@@ -513,6 +513,9 @@ features! {
 
     /// Allow multiple packages to participate in the same API namespace
     (unstable, open_namespaces, "", "reference/unstable.html#open-namespaces"),
+
+    /// Allow paths that resolve relatively to a base specified in the config.
+    (unstable, path_bases, "", "reference/unstable.html#path-bases"),
 }
 
 /// Status and metadata for a single unstable feature.

src/cargo/util/toml/mod.rs

@@ -10,7 +10,9 @@ use crate::AlreadyPrintedError;
 use anyhow::{anyhow, bail, Context as _};
 use cargo_platform::Platform;
 use cargo_util::paths::{self, normalize_path};
-use cargo_util_schemas::manifest::{self, TomlManifest};
+use cargo_util_schemas::manifest::{
+    self, PackageName, PathBaseName, TomlDependency, TomlDetailedDependency, TomlManifest,
+};
 use cargo_util_schemas::manifest::{RustVersion, StringOrBool};
 use itertools::Itertools;
 use lazycell::LazyCell;
@@ -296,7 +298,7 @@ fn normalize_toml(
         features: None,
         target: None,
         replace: original_toml.replace.clone(),
-        patch: original_toml.patch.clone(),
+        patch: None,
         workspace: original_toml.workspace.clone(),
         badges: None,
         lints: None,
@@ -305,11 +307,18 @@ fn normalize_toml(
 
     let package_root = manifest_file.parent().unwrap();
 
-    let inherit_cell: LazyCell<InheritableFields> = LazyCell::new();
-    let inherit = || {
+    let inherit_cell: LazyCell<Option<InheritableFields>> = LazyCell::new();
+    let load_inherit = || {
         inherit_cell
             .try_borrow_with(|| load_inheritable_fields(gctx, manifest_file, &workspace_config))
     };
+    let inherit = || {
+        load_inherit()?
+            .as_ref()
+            .ok_or_else(|| anyhow!("failed to find a workspace root"))
+    };
+    let workspace_root =
+        || load_inherit().map(|inherit| inherit.as_ref().map(|fields| fields.ws_root()));
 
     if let Some(original_package) = original_toml.package() {
         let package_name = &original_package.name;
@@ -390,6 +399,7 @@ fn normalize_toml(
             &activated_opt_deps,
             None,
             &inherit,
+            &workspace_root,
             package_root,
             warnings,
         )?;
@@ -410,6 +420,7 @@ fn normalize_toml(
             &activated_opt_deps,
             Some(DepKind::Development),
             &inherit,
+            &workspace_root,
             package_root,
             warnings,
         )?;
@@ -430,6 +441,7 @@ fn normalize_toml(
             &activated_opt_deps,
             Some(DepKind::Build),
             &inherit,
+            &workspace_root,
             package_root,
             warnings,
         )?;
@@ -443,6 +455,7 @@ fn normalize_toml(
                 &activated_opt_deps,
                 None,
                 &inherit,
+                &workspace_root,
                 package_root,
                 warnings,
             )?;
@@ -463,6 +476,7 @@ fn normalize_toml(
                 &activated_opt_deps,
                 Some(DepKind::Development),
                 &inherit,
+                &workspace_root,
                 package_root,
                 warnings,
             )?;
@@ -483,6 +497,7 @@ fn normalize_toml(
                 &activated_opt_deps,
                 Some(DepKind::Build),
                 &inherit,
+                &workspace_root,
                 package_root,
                 warnings,
             )?;
@@ -499,6 +514,13 @@ fn normalize_toml(
         }
         normalized_toml.target = (!normalized_target.is_empty()).then_some(normalized_target);
 
+        normalized_toml.patch = normalize_patch(
+            gctx,
+            original_toml.patch.as_ref(),
+            &workspace_root,
+            features,
+        )?;
+
         let normalized_lints = original_toml
             .lints
             .clone()
@@ -519,6 +541,37 @@ fn normalize_toml(
     Ok(normalized_toml)
 }
 
+fn normalize_patch<'a>(
+    gctx: &GlobalContext,
+    original_patch: Option<&BTreeMap<String, BTreeMap<PackageName, TomlDependency>>>,
+    workspace_root: &dyn Fn() -> CargoResult<Option<&'a PathBuf>>,
+    features: &Features,
+) -> CargoResult<Option<BTreeMap<String, BTreeMap<PackageName, TomlDependency>>>> {
+    if let Some(patch) = original_patch {
+        let mut normalized_patch = BTreeMap::new();
+        for (name, packages) in patch {
+            let mut normalized_packages = BTreeMap::new();
+            for (pkg, dep) in packages {
+                let dep = if let TomlDependency::Detailed(dep) = dep {
+                    let mut dep = dep.clone();
+                    normalize_path_dependency(gctx, &mut dep, workspace_root, features)
+                        .with_context(|| {
+                            format!("resolving path for patch of ({pkg}) for source ({name})")
+                        })?;
+                    TomlDependency::Detailed(dep)
+                } else {
+                    dep.clone()
+                };
+                normalized_packages.insert(pkg.clone(), dep);
+            }
+            normalized_patch.insert(name.clone(), normalized_packages);
+        }
+        Ok(Some(normalized_patch))
+    } else {
+        Ok(None)
+    }
+}
+
 #[tracing::instrument(skip_all)]
 fn normalize_package_toml<'a>(
     original_package: &manifest::TomlPackage,
@@ -710,6 +763,7 @@ fn normalize_dependencies<'a>(
     activated_opt_deps: &HashSet<&str>,
     kind: Option<DepKind>,
     inherit: &dyn Fn() -> CargoResult<&'a InheritableFields>,
+    workspace_root: &dyn Fn() -> CargoResult<Option<&'a PathBuf>>,
     package_root: &Path,
     warnings: &mut Vec<String>,
 ) -> CargoResult<Option<BTreeMap<manifest::PackageName, manifest::InheritableDependency>>> {
@@ -768,6 +822,8 @@ fn normalize_dependencies<'a>(
                     }
                 }
             }
+            normalize_path_dependency(gctx, d, workspace_root, features)
+                .with_context(|| format!("resolving path dependency ({name_in_toml})"))?;
         }
 
         // if the dependency is not optional, it is always used
@@ -786,13 +842,30 @@ fn normalize_dependencies<'a>(
     Ok(Some(deps))
 }
 
+fn normalize_path_dependency<'a>(
+    gctx: &GlobalContext,
+    detailed_dep: &mut TomlDetailedDependency,
+    workspace_root: &dyn Fn() -> CargoResult<Option<&'a PathBuf>>,
+    features: &Features,
+) -> CargoResult<()> {
+    if let Some(base) = detailed_dep.base.take() {
+        if let Some(path) = detailed_dep.path.as_mut() {
+            let new_path = lookup_path_base(&base, gctx, workspace_root, features)?.join(&path);
+            *path = new_path.to_str().unwrap().to_string();
+        } else {
+            bail!("`base` can only be used with path dependencies");
+        }
+    }
+    Ok(())
+}
+
 fn load_inheritable_fields(
     gctx: &GlobalContext,
     normalized_path: &Path,
     workspace_config: &WorkspaceConfig,
-) -> CargoResult<InheritableFields> {
+) -> CargoResult<Option<InheritableFields>> {
     match workspace_config {
-        WorkspaceConfig::Root(root) => Ok(root.inheritable().clone()),
+        WorkspaceConfig::Root(root) => Ok(Some(root.inheritable().clone())),
         WorkspaceConfig::Member {
             root: Some(ref path_to_root),
         } => {
@@ -802,14 +875,11 @@ fn load_inheritable_fields(
                 .join(path_to_root)
                 .join("Cargo.toml");
             let root_path = paths::normalize_path(&path);
-            inheritable_from_path(gctx, root_path)
-        }
-        WorkspaceConfig::Member { root: None } => {
-            match find_workspace_root(&normalized_path, gctx)? {
-                Some(path_to_root) => inheritable_from_path(gctx, path_to_root),
-                None => Err(anyhow!("failed to find a workspace root")),
-            }
+            inheritable_from_path(gctx, root_path).map(Some)
         }
+        WorkspaceConfig::Member { root: None } => find_workspace_root(&normalized_path, gctx)?
+            .map(|path_to_root| inheritable_from_path(gctx, path_to_root))
+            .transpose(),
     }
 }
 
@@ -901,13 +971,17 @@ impl InheritableFields {
         };
         let mut dep = dep.clone();
         if let manifest::TomlDependency::Detailed(detailed) = &mut dep {
-            if let Some(rel_path) = &detailed.path {
-                detailed.path = Some(resolve_relative_path(
-                    name,
-                    self.ws_root(),
-                    package_root,
-                    rel_path,
-                )?);
+            if detailed.base.is_none() {
+                // If this is a path dependency without a base, then update the path to be relative
+                // to the workspace root instead.
+                if let Some(rel_path) = &detailed.path {
+                    detailed.path = Some(resolve_relative_path(
+                        name,
+                        self.ws_root(),
+                        package_root,
+                        rel_path,
+                    )?);
+                }
             }
         }
         Ok(dep)
@@ -2151,6 +2225,41 @@ fn to_dependency_source_id<P: ResolveToPath + Clone>(
     }
 }
 
+pub(crate) fn lookup_path_base<'a>(
+    base: &PathBaseName,
+    gctx: &GlobalContext,
+    workspace_root: &dyn Fn() -> CargoResult<Option<&'a PathBuf>>,
+    features: &Features,
+) -> CargoResult<PathBuf> {
+    features.require(Feature::path_bases())?;
+
+    // Look up the relevant base in the Config and use that as the root.
+    // NOTE: The `base` string is user controlled, but building the path is safe from injection
+    // attacks since the `PathBaseName` type restricts the characters that can be used.
+    if let Some(path_bases) =
+        gctx.get::<Option<ConfigRelativePath>>(&format!("path-bases.{base}"))?
+    {
+        Ok(path_bases.resolve_path(gctx))
+    } else {
+        // Otherwise, check the built-in bases.
+        match base.as_str() {
+            "workspace" => {
+                if let Some(workspace_root) = workspace_root()? {
+                    Ok(workspace_root.clone())
+                } else {
+                    bail!(
+                        "the `workspace` built-in path base cannot be used outside of a workspace."
+                    )
+                }
+            }
+            _ => bail!(
+                "path base `{base}` is undefined. \
+            You must add an entry for `{base}` in the Cargo configuration [path-bases] table."
+            ),
+        }
+    }
+}
+
 pub trait ResolveToPath {
     fn resolve(&self, gctx: &GlobalContext) -> PathBuf;
 }
@@ -2865,6 +2974,7 @@ fn prepare_toml_for_publish(
                 let mut d = d.clone();
                 // Path dependencies become crates.io deps.
                 d.path.take();
+                d.base.take();
                 // Same with git dependencies.
                 d.git.take();
                 d.branch.take();