add generic sparse registry support, use it for crates.io

Cargo.toml

@@ -14,9 +14,10 @@ readme = "README.md"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [features]
-default = ["alternate-registries"]
+default = ["git-registries"]
 
-alternate-registries = ["dep:git2"]
+git-registries = ["dep:git2"]
+alternate-registries = ["git-registries"]
 unstable = []
 unstable-toolchain-ci = []
 tracing = ["dep:tracing"]
@@ -35,6 +36,7 @@ flate2 = "1"
 tar = "0.4.0"
 percent-encoding = "2.1.0"
 walkdir = "2.2"
+url = "2.5"
 toml = "1.1.2"
 remove_dir_all = "1.0.0"
 base64 = "0.23.0"
@@ -54,3 +56,4 @@ env_logger = "0.11.3"
 rand = "0.10.0"
 test-case = "3.3.1"
 tiny_http = "0.12.0"
+mockito = "1"

src/crates/mod.rs

@@ -2,12 +2,16 @@ mod git;
 mod local;
 mod registry;
 
-use crate::Workspace;
+use crate::{Workspace, crates::registry::CRATES_IO_SPARSE_INDEX};
+use anyhow::{Context as _, Result};
 use log::info;
 use std::path::Path;
+use url::Url;
 
-#[cfg(feature = "alternate-registries")]
-pub use registry::AlternativeRegistry;
+#[cfg(feature = "git-registries")]
+pub use registry::GitRegistry;
+#[cfg(feature = "git-registries")]
+pub use registry::GitRegistry as AlternativeRegistry;
 
 trait CrateTrait: std::fmt::Display {
     fn fetch(&self, workspace: &Workspace) -> anyhow::Result<()>;
@@ -25,25 +29,48 @@ enum CrateType {
 pub struct Crate(CrateType);
 
 impl Crate {
-    /// Load a crate from specified registry.
-    #[cfg(feature = "alternate-registries")]
-    pub fn registry(registry: AlternativeRegistry, name: &str, version: &str) -> Self {
-        Crate(CrateType::Registry(registry::RegistryCrate::new(
-            registry::Registry::Alternative(registry),
+    /// Load a crate from a sparse registry index.
+    ///
+    /// `index` is the URL of the registry index, with or without Cargo's `sparse+` prefix.
+    /// Its `config.json` is cached in the workspace after the first fetch.
+    pub fn sparse_registry<U>(index: U, name: &str, version: &str) -> Result<Self>
+    where
+        U: TryInto<Url>,
+        <U as TryInto<Url>>::Error: std::error::Error + Send + Sync + 'static,
+    {
+        let index = index.try_into().context("invalid index url")?;
+
+        Ok(Crate(CrateType::Registry(registry::RegistryCrate::new(
+            registry::Registry::Sparse(registry::normalize_sparse_index(index)?),
             name,
             version,
-        )))
+        ))))
     }
 
-    /// Load a crate from the [crates.io registry](https://crates.io).
-    pub fn crates_io(name: &str, version: &str) -> Self {
+    /// Load a crate from a Git-indexed registry.
+    ///
+    /// For an HTTP sparse index, use [`Crate::sparse_registry`].
+    #[cfg(feature = "git-registries")]
+    pub fn git_registry(registry: GitRegistry, name: &str, version: &str) -> Self {
         Crate(CrateType::Registry(registry::RegistryCrate::new(
-            registry::Registry::CratesIo,
+            registry::Registry::Git(registry),
             name,
             version,
         )))
     }
 
+    /// Compatibility alias for [`Crate::git_registry`].
+    #[cfg(feature = "git-registries")]
+    pub fn registry(registry: AlternativeRegistry, name: &str, version: &str) -> Self {
+        Self::git_registry(registry, name, version)
+    }
+
+    /// Load a crate from the [crates.io registry](https://crates.io).
+    pub fn crates_io(name: &str, version: &str) -> Self {
+        Self::sparse_registry(CRATES_IO_SPARSE_INDEX.clone(), name, version)
+            .expect("we know crates.io index url is valid")
+    }
+
     /// Load a crate from a git repository. The full URL needed to clone the repo has to be
     /// provided.
     pub fn git(url: &str) -> Self {