Auto merge of #11870 - epage:registry, r=Eh2406

docs(contrib): Move higher level resolver docs into doc comments

This is a follow up to #11809.

I chose `ops::resolve` for most of the old documentation as this because the docs cover the
higher level details that include it, like `Cargo.lock` file, while
`core::resolver` is more of the algorithm.

src/cargo/core/resolver/mod.rs

@@ -37,6 +37,17 @@
 //! everything to bail out immediately and return success, and only if *nothing*
 //! works do we actually return an error up the stack.
 //!
+//! Resolution is currently performed twice
+//! 1. With all features enabled (this is what gets saved to `Cargo.lock`)
+//! 2. With only the specific features the user selected on the command-line. Ideally this
+//!    run will get removed in the future when transitioning to the new feature resolver.
+//!
+//! A new feature-specific resolver was added in 2020 which adds more sophisticated feature
+//! resolution. It is located in the [`features`] module. The original dependency resolver still
+//! performs feature unification, as it can help reduce the dependencies it has to consider during
+//! resolution (rather than assuming every optional dependency of every package is enabled).
+//! Checking if a feature is enabled must go through the new feature resolver.
+//!
 //! ## Performance
 //!
 //! Note that this is a relatively performance-critical portion of Cargo. The

src/cargo/lib.rs

@@ -31,8 +31,9 @@
 //!     This is the entry point for all the compilation commands. This is a
 //!     good place to start if you want to follow how compilation starts and
 //!     flows to completion.
-//! - [`core::resolver`]:
-//!   This is the dependency and feature resolvers.
+//! - [`ops::resolve`]:
+//!   Top-level API for dependency and feature resolver (e.g. [`ops::resolve_ws`])
+//!   - [`core::resolver`]: The core algorithm
 //! - [`core::compiler`]:
 //!   This is the code responsible for running `rustc` and `rustdoc`.
 //!   - [`core::compiler::build_context`]:

src/cargo/ops/mod.rs

@@ -53,7 +53,7 @@ mod common_for_install_and_uninstall;
 mod fix;
 pub(crate) mod lockfile;
 pub(crate) mod registry;
-mod resolve;
+pub(crate) mod resolve;
 pub mod tree;
 mod vendor;
 

src/cargo/ops/resolve.rs

@@ -1,14 +1,59 @@
 //! High-level APIs for executing the resolver.
 //!
-//! This module provides functions for running the resolver given a workspace.
+//! This module provides functions for running the resolver given a workspace, including loading
+//! the `Cargo.lock` file and checkinf if it needs updating.
+//!
 //! There are roughly 3 main functions:
 //!
-//! - `resolve_ws`: A simple, high-level function with no options.
-//! - `resolve_ws_with_opts`: A medium-level function with options like
+//! - [`resolve_ws`]: A simple, high-level function with no options.
+//! - [`resolve_ws_with_opts`]: A medium-level function with options like
 //!   user-provided features. This is the most appropriate function to use in
 //!   most cases.
-//! - `resolve_with_previous`: A low-level function for running the resolver,
+//! - [`resolve_with_previous`]: A low-level function for running the resolver,
 //!   providing the most power and flexibility.
+//!
+//! ### Data Structures
+//!
+//! - [`Workspace`]:
+//!   Usually created by [`crate::util::command_prelude::ArgMatchesExt::workspace`] which discovers the root of the
+//!   workspace, and loads all the workspace members as a [`Package`] object
+//!   - [`Package`]
+//!     Corresponds with `Cargo.toml` manifest (deserialized as [`Manifest`]) and its associated files.
+//!     - [`Target`]s are crates such as the library, binaries, integration test, or examples.
+//!       They are what is actually compiled by `rustc`.
+//!       Each `Target` defines a crate root, like `src/lib.rs` or `examples/foo.rs`.
+//!     - [`PackageId`] --- A unique identifier for a package.
+//! - [`PackageRegistry`]:
+//!   The primary interface for how the dependency
+//!   resolver finds packages. It contains the `SourceMap`, and handles things
+//!   like the `[patch]` table. The dependency resolver
+//!   sends a query to the `PackageRegistry` to "get me all packages that match
+//!   this dependency declaration". The `Registry` trait provides a generic interface
+//!   to the `PackageRegistry`, but this is only used for providing an alternate
+//!   implementation of the `PackageRegistry` for testing.
+//! - [`SourceMap`]: Map of all available sources.
+//!   - [`Source`]: An abstraction for something that can fetch packages (a remote
+//!     registry, a git repo, the local filesystem, etc.). Check out the [source
+//!     implementations] for all the details about registries, indexes, git
+//!     dependencies, etc.
+//!       * [`SourceId`]: A unique identifier for a source.
+//!   - [`Summary`]: A of a [`Manifest`], and is essentially
+//!     the information that can be found in a registry index. Queries against the
+//!     `PackageRegistry` yields a `Summary`. The resolver uses the summary
+//!     information to build the dependency graph.
+//! - [`PackageSet`] --- Contains all of the `Package` objects. This works with the
+//!   [`Downloads`] struct to coordinate downloading packages. It has a reference
+//!   to the `SourceMap` to get the `Source` objects which tell the `Downloads`
+//!   struct which URLs to fetch.
+//!
+//! [`Package`]: crate::core::package
+//! [`Target`]: crate::core::Target
+//! [`Manifest`]: crate::core::Manifest
+//! [`Source`]: crate::core::Source
+//! [`SourceMap`]: crate::core::SourceMap
+//! [`PackageRegistry`]: crate::core::registry::PackageRegistry
+//! [source implementations]: crate::sources
+//! [`Downloads`]: crate::core::package::Downloads
 
 use crate::core::compiler::{CompileKind, RustcTargetData};
 use crate::core::registry::{LockedPatchDependency, PackageRegistry};

src/doc/contrib/src/architecture/packages.md

@@ -1,92 +1,3 @@
 # Packages and Resolution
 
-## Workspaces
-
-The [`Workspace`] object is usually created very early by calling the
-[`workspace`][ws-method] helper method. This discovers the root of the
-workspace, and loads all the workspace members as a [`Package`] object. Each
-package corresponds to a single `Cargo.toml` (which is deserialized into a
-[`Manifest`]), and may define several [`Target`]s, such as the library,
-binaries, integration test or examples. Targets are crates (each target
-defines a crate root, like `src/lib.rs` or `examples/foo.rs`) and are what is
-actually compiled by `rustc`.
-
-## Packages and Sources
-
-There are several data structures that are important to understand how
-packages are found and loaded:
-
-* [`Package`] --- A package, which is a `Cargo.toml` manifest and its associated
-  source files.
-    * [`PackageId`] --- A unique identifier for a package.
-* [`Source`] --- An abstraction for something that can fetch packages (a remote
-  registry, a git repo, the local filesystem, etc.). Check out the [source
-  implementations] for all the details about registries, indexes, git
-  dependencies, etc.
-    * [`SourceId`] --- A unique identifier for a source.
-* [`SourceMap`] --- Map of all available sources.
-* [`PackageRegistry`] --- This is the main interface for how the dependency
-  resolver finds packages. It contains the `SourceMap`, and handles things
-  like the `[patch]` table. The `Registry` trait provides a generic interface
-  to the `PackageRegistry`, but this is only used for providing an alternate
-  implementation of the `PackageRegistry` for testing. The dependency resolver
-  sends a query to the `PackageRegistry` to "get me all packages that match
-  this dependency declaration".
-* [`Summary`] --- A summary is a subset of a [`Manifest`], and is essentially
-  the information that can be found in a registry index. Queries against the
-  `PackageRegistry` yields a `Summary`. The resolver uses the summary
-  information to build the dependency graph.
-* [`PackageSet`] --- Contains all of the `Package` objects. This works with the
-  [`Downloads`] struct to coordinate downloading packages. It has a reference
-  to the `SourceMap` to get the `Source` objects which tell the `Downloads`
-  struct which URLs to fetch.
-
-All of these come together in the [`ops::resolve`] module. This module
-contains the primary functions for performing resolution (described below). It
-also handles downloading of packages. It is essentially where all of the data
-structures above come together.
-
-## Resolver
-
-[`Resolve`] is the representation of a directed graph of package dependencies,
-which uses [`PackageId`]s for nodes. This is the data structure that is saved
-to the `Cargo.lock` file. If there is no lock file, Cargo constructs a resolve
-by finding a graph of packages which matches declared dependency specification
-according to SemVer.
-
-[`ops::resolve`] is the front-end for creating a `Resolve`. It handles loading
-the `Cargo.lock` file, checking if it needs updating, etc.
-
-Resolution is currently performed twice. It is performed once with all
-features enabled. This is the resolve that gets saved to `Cargo.lock`. It then
-runs again with only the specific features the user selected on the
-command-line. Ideally this second run will get removed in the future when
-transitioning to the new feature resolver.
-
-### Feature resolver
-
-A new feature-specific resolver was added in 2020 which adds more
-sophisticated feature resolution. It is located in the [`resolver::features`]
-module. The original dependency resolver still performs feature unification,
-as it can help reduce the dependencies it has to consider during resolution
-(rather than assuming every optional dependency of every package is enabled).
-Checking if a feature is enabled must go through the new feature resolver.
-
-
-[`Workspace`]: https://github.com/rust-lang/cargo/blob/master/src/cargo/core/workspace.rs
-[ws-method]: https://github.com/rust-lang/cargo/blob/e4b65bdc80f2a293447f2f6a808fa7c84bf9a357/src/cargo/util/command_prelude.rs#L298-L318
-[`Package`]: https://github.com/rust-lang/cargo/blob/master/src/cargo/core/package.rs
-[`Target`]: https://github.com/rust-lang/cargo/blob/e4b65bdc80f2a293447f2f6a808fa7c84bf9a357/src/cargo/core/manifest.rs#L181-L206
-[`Manifest`]: https://github.com/rust-lang/cargo/blob/e4b65bdc80f2a293447f2f6a808fa7c84bf9a357/src/cargo/core/manifest.rs#L27-L51
-[`Source`]: https://github.com/rust-lang/cargo/blob/master/src/cargo/core/source/mod.rs
-[`SourceId`]: https://github.com/rust-lang/cargo/blob/master/src/cargo/core/source/source_id.rs
-[`SourceMap`]: https://github.com/rust-lang/cargo/blob/e4b65bdc80f2a293447f2f6a808fa7c84bf9a357/src/cargo/core/source/mod.rs#L245-L249
-[`PackageRegistry`]: https://github.com/rust-lang/cargo/blob/e4b65bdc80f2a293447f2f6a808fa7c84bf9a357/src/cargo/core/registry.rs#L36-L81
-[`ops::resolve`]: https://github.com/rust-lang/cargo/blob/master/src/cargo/ops/resolve.rs
-[`resolver::features`]: https://github.com/rust-lang/cargo/blob/master/src/cargo/core/resolver/features.rs#L259
-[source implementations]: https://github.com/rust-lang/cargo/tree/master/src/cargo/sources
-[`PackageId`]: https://github.com/rust-lang/cargo/blob/master/src/cargo/core/package_id.rs
-[`Summary`]: https://github.com/rust-lang/cargo/blob/master/src/cargo/core/summary.rs
-[`PackageSet`]: https://github.com/rust-lang/cargo/blob/e4b65bdc80f2a293447f2f6a808fa7c84bf9a357/src/cargo/core/package.rs#L283-L296
-[`Downloads`]: https://github.com/rust-lang/cargo/blob/e4b65bdc80f2a293447f2f6a808fa7c84bf9a357/src/cargo/core/package.rs#L298-L352
-[`Resolve`]: https://github.com/rust-lang/cargo/blob/master/src/cargo/core/resolver/resolve.rs
+See [nightly docs](https://doc.rust-lang.org/nightly/nightly-rustc/cargo/index.html)