Auto merge of #10497 - Muscraft:rfc2906-part1, r=epage

Part 1 of RFC2906 - Packages can inherit fields from their root workspace

Tracking issue: #8415
RFC: rust-lang/rfcs#2906

All changes were heavily inspired by #8664 and #9684

A big thanks to both `@yaymukund` and `@ParkMyCar.` I pulled a lot of inspiration from their branches.

I would also like to thank `@alexcrichton` for all the feedback on the first attempt. It has brought this into a much better state.

All changes have been made according to the RFC as well as `@alexcrichton's` [comment](#8664 (comment)).

This is part 1 of many, as described by [this comment](#9684 (comment)), [this comment](#9684 (review)) and redefined  [by this one](#10497 (comment)).

This PR focuses on inheriting in root package, including:
- Add `MaybeWorkspace<T>` to allow for `{ workspace = true }`
- Add a new variant to `TomlDependency` to allow inheriting dependencies from a workspace
- Add `InheritableFields` so that we have somewhere to get a value from when we `resolve` a `MaybeWorkspace<T>`
  - `license_file` and `readme` are in `InheritableFields` in this part but are not `MaybeWorkspace` for reasons [described here](#10497 (comment))
- Add a method to `resolve` a `MaybeWorkspace<T>` into a `T` that can fail if we have nowhere to pull from or the workspace does not define that field
- Disallow inheriting from a different `Cargo.toml`
  - This means that you can only inherit from inside the same `Cargo.toml`, i.e. it has both a `[workspace]` and a `[package]`
  - Forcing this requirement allows us to test the implementations of `MaybeWorkspace<T>` and the new `TomlDependency` variant without having to add searching for a workspace root and the complexity with it

Remaining implementation work for the RFC
- Support inheriting in any workspace member
- Correctly inherit fields that are relative paths
  - Including adding support for inheriting `license_file`,  `readme`, and path-dependencies
-  Path dependencies infer version directive
- Lock workspace dependencies and warn when unused
- Optimizations, as needed
- Evaluate any new fields for being inheritable (e.g. `rust-version`)
- Evaluate making users of `{ workspace = true }` define the workspace they pull from in `[package]`

Areas of concern:
- `TomlDependency` Deserialization is a mess, and I could not figure out how to do it in a cleaner way without significant headaches. I ended up having to do the same thing as last time [which was an issue](#9684 (comment)).
- Resolving on a `MaybeWorkspace` feels extremely verbose currently:
  ```rust
  project.homepage.clone().map(|mw| mw.resolve(&features, "homepage", || get_ws(inheritable)?.homepage())).transpose()?,
  ```
  This way allows for lazy resolution of inheritable fields and finding a workspace (in part 2) so you do not pay a penalty for not using this feature. The other bit of good news is `&features` will go away as it is just feature checking currently.

- This feature requires some level of duplication of code as well as remaking the original `TomlManifest` which adds extra length to the changes.
- This feature also takes a linear process and makes it potentially non-linear which adds lots of complexity (which will get worse in Part 2)

Please let me know if you have any feedback or suggestions!

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

@@ -4,7 +4,7 @@ use std::collections::{BTreeMap, BTreeSet, HashSet};
 use std::path::{Path, PathBuf};
 use std::rc::Rc;
 
-use anyhow::{bail, Context as _};
+use anyhow::{anyhow, bail, Context as _};
 use glob::glob;
 use itertools::Itertools;
 use log::debug;
@@ -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>,
 }
 
@@ -1567,17 +1579,18 @@ 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 {
             root_dir: root_dir.to_path_buf(),
             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 +1654,190 @@ 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) -> CargoResult<BTreeMap<String, TomlDependency>> {
+        self.dependencies.clone().map_or(
+            Err(anyhow!("`workspace.dependencies` was not defined")),
+            |d| Ok(d),
+        )
+    }
+
+    pub fn get_dependency(&self, name: &str) -> CargoResult<TomlDependency> {
+        self.dependencies.clone().map_or(
+            Err(anyhow!("`workspace.dependencies` was not defined")),
+            |deps| {
+                deps.get(name).map_or(
+                    Err(anyhow!(
+                        "`dependency.{}` was not found in `workspace.dependencies`",
+                        name
+                    )),
+                    |dep| Ok(dep.clone()),
+                )
+            },
+        )
+    }
+
+    pub fn version(&self) -> CargoResult<semver::Version> {
+        self.version
+            .clone()
+            .map_or(Err(anyhow!("`workspace.version` was not defined")), |d| {
+                Ok(d)
+            })
+    }
+
+    pub fn authors(&self) -> CargoResult<Vec<String>> {
+        self.authors
+            .clone()
+            .map_or(Err(anyhow!("`workspace.authors` was not defined")), |d| {
+                Ok(d)
+            })
+    }
+
+    pub fn description(&self) -> CargoResult<String> {
+        self.description.clone().map_or(
+            Err(anyhow!("`workspace.description` was not defined")),
+            |d| Ok(d),
+        )
+    }
+
+    pub fn homepage(&self) -> CargoResult<String> {
+        self.homepage
+            .clone()
+            .map_or(Err(anyhow!("`workspace.homepage` was not defined")), |d| {
+                Ok(d)
+            })
+    }
+
+    pub fn documentation(&self) -> CargoResult<String> {
+        self.documentation.clone().map_or(
+            Err(anyhow!("`workspace.documentation` was not defined")),
+            |d| Ok(d),
+        )
+    }
+
+    pub fn readme(&self) -> CargoResult<StringOrBool> {
+        self.readme
+            .clone()
+            .map_or(Err(anyhow!("`workspace.readme` was not defined")), |d| {
+                Ok(d)
+            })
+    }
+
+    pub fn keywords(&self) -> CargoResult<Vec<String>> {
+        self.keywords
+            .clone()
+            .map_or(Err(anyhow!("`workspace.keywords` was not defined")), |d| {
+                Ok(d)
+            })
+    }
+
+    pub fn categories(&self) -> CargoResult<Vec<String>> {
+        self.categories.clone().map_or(
+            Err(anyhow!("`workspace.categories` was not defined")),
+            |d| Ok(d),
+        )
+    }
+
+    pub fn license(&self) -> CargoResult<String> {
+        self.license
+            .clone()
+            .map_or(Err(anyhow!("`workspace.license` was not defined")), |d| {
+                Ok(d)
+            })
+    }
+
+    pub fn license_file(&self) -> CargoResult<String> {
+        self.license_file.clone().map_or(
+            Err(anyhow!("`workspace.license_file` was not defined")),
+            |d| Ok(d),
+        )
+    }
+
+    pub fn repository(&self) -> CargoResult<String> {
+        self.repository.clone().map_or(
+            Err(anyhow!("`workspace.repository` was not defined")),
+            |d| Ok(d),
+        )
+    }
+
+    pub fn publish(&self) -> CargoResult<VecStringOrBool> {
+        self.publish
+            .clone()
+            .map_or(Err(anyhow!("`workspace.publish` was not defined")), |d| {
+                Ok(d)
+            })
+    }
+
+    pub fn edition(&self) -> CargoResult<String> {
+        self.edition
+            .clone()
+            .map_or(Err(anyhow!("`workspace.edition` was not defined")), |d| {
+                Ok(d)
+            })
+    }
+
+    pub fn badges(&self) -> CargoResult<BTreeMap<String, BTreeMap<String, String>>> {
+        self.badges
+            .clone()
+            .map_or(Err(anyhow!("`workspace.badges` was not defined")), |d| {
+                Ok(d)
+            })
+    }
+}