Rework Toolchain model and drop relative file path overrides

Relative path overrides permit a freshly downloaded source tree to
execute arbitrary code on any rustup command that executes a binary from
the configured toolchain, and its a reasonable tradeoff for us to remove
this feature. Absolute path overrides are kept intact - these were added
to support users of large monorepo tool systems, and can be kept with
reasonable safety.

Introduce an interior model for toolchain names which allows the
elimination of conditional code for custom vs named vs path based
toolchains. Fixes #3130.

Finishes the separation of Toolchain vs DistributableToolchain vs
CustomToolchain started some time ago.

Moves some test support into the src tree in order to keep symbols
private and adds a 'test' feature required for self-testing, ensuring
that that code doesn't affect production builds.

Author: rbtcollins

CONTRIBUTING.md

@@ -2,7 +2,7 @@
 
 1. Fork it!
 2. Create your feature branch: `git checkout -b my-new-feature`
-3. Test it: `cargo test`
+3. Test it: `cargo test --features=test`
 4. Lint it: `cargo +beta clippy --all --all-targets -- -D warnings`
 > We use `cargo clippy` to ensure high-quality code and to enforce a set of best practices for Rust programming. However, not all lints provided by `cargo clippy` are relevant or applicable to our project.
 > We may choose to ignore some lints if they are unstable, experimental, or specific to our project.
@@ -312,7 +312,7 @@ And [look in Jaeger for a trace](http://localhost:16686/search?service=rustup).
 
 The custom macro `rustup_macros::test` adds a prelude and suffix to each test to
 ensure that there is a tracing context setup, that the test function is a span,
-and that the spans from the test are flushed. Build with features=otel to
+and that the spans from the test are flushed. Build with features=otel,test to
 use this feature.
 
 ### Adding instrumentation

Cargo.lock

@@ -41,28 +41,29 @@ otel = [
     "dep:tokio",
 ]
 
+# Exports code dependent on private interfaces for the integration test suite
+test = ["dep:once_cell", "dep:walkdir"]
+
 # Sorted by alphabetic order
 [dependencies]
 anyhow.workspace = true
 cfg-if = "1.0"
 chrono = "0.4"
 clap = { version = "3", features = ["wrap_help"] }
 clap_complete = "3"
+derivative.workspace = true
 download = { path = "download", default-features = false }
 effective-limits = "0.5.5"
 enum-map = "2.5.0"
 flate2 = "1"
+fs_at.workspace = true
 git-testament = "0.2"
 home = "0.5.4"
 lazy_static.workspace = true
 libc = "0.2"
 num_cpus = "1.15"
-once_cell.workspace = true
+once_cell = { workspace = true, optional = true }
 opener = "0.6.0"
-# Used by `curl` or `reqwest` backend although it isn't imported by our rustup :
-# this allows controlling the vendoring status without exposing the presence of
-# the download crate.
-openssl = { version = "0.10", optional = true }
 opentelemetry = { workspace = true, optional = true }
 opentelemetry-otlp = { workspace = true, optional = true }
 pulldown-cmark = { version = "0.9", default-features = false }
@@ -78,8 +79,7 @@ sharded-slab = "0.1.1"
 strsim = "0.10"
 tar = "0.4.26"
 tempfile.workspace = true
-# FIXME(issue #1818, #1826, and friends)
-term = "=0.5.1"
+term = "=0.5.1" # FIXME(issue #1818, #1826, and friends)
 thiserror.workspace = true
 threadpool = "1"
 tokio = { workspace = true, optional = true }
@@ -91,9 +91,17 @@ tracing-subscriber = { workspace = true, optional = true, features = [
 tracing.workspace = true
 url.workspace = true
 wait-timeout = "0.2"
+walkdir = { workspace = true, optional = true }
 xz2 = "0.1.3"
 zstd = "0.12"
 
+[dependencies.openssl]
+# Used by `curl` or `reqwest` backend although it isn't imported by our rustup :
+# this allows controlling the vendoring status without exposing the presence of
+# the download crate.
+optional = true
+version = "0.10"
+
 [dependencies.retry]
 default-features = false
 features = ["random"]
@@ -133,13 +141,27 @@ features = [
 ]
 version = "0.3"
 
+[target."cfg(windows)".dependencies.windows-sys]
+features = [
+    "Win32_Foundation",
+    "Win32_Storage_FileSystem",
+    "Win32_System_SystemServices",
+    "Win32_System_Threading",
+    "Win32_System_WindowsProgramming",
+    "Win32_Security",
+    "Win32_System_Kernel",
+    "Win32_System_IO",
+    "Win32_System_Ioctl",
+]
+version = "0.45.0"
+
+
 [dev-dependencies]
 enum-map = "2.5.0"
 once_cell.workspace = true
 rustup-macros.workspace = true
 tokio = { workspace = true, features = ["rt-multi-thread", "macros"] }
 trycmd = "0.14.13"
-walkdir = "2"
 
 [build-dependencies]
 lazy_static = "1"
@@ -150,6 +172,8 @@ members = ["download", "rustup-macros"]
 
 [workspace.dependencies]
 anyhow = "1.0.69"
+derivative = "2.2.0"
+fs_at = "0.1.6"
 lazy_static = "1"
 once_cell = "1.17.1"
 opentelemetry = { version = "0.18.0", features = ["rt-tokio"] }
@@ -162,6 +186,7 @@ tracing = "0.1"
 tracing-opentelemetry = { version = "0.18.0" }
 tracing-subscriber = "0.3.16"
 url = "2.3"
+walkdir = "2"
 
 [lib]
 name = "rustup"

Cargo.toml

@@ -25,6 +25,12 @@ case "$TARGET" in
   * ) FEATURES+=('--features' 'reqwest-rustls-tls') ;;
 esac
 
+case "$BUILD_PROFILE" in 
+  release ) ;;
+  # Default case, includes tests, build tests and otel
+  * ) FEATURES+=('--features' 'otel,test') ;;
+esac
+
 # rustc only supports armv7: https://doc.rust-lang.org/nightly/rustc/platform-support.html
 if [ "$TARGET" = arm-linux-androideabi ]; then
   export CFLAGS='-march=armv7'

ci/run.bash

@@ -4,9 +4,10 @@
   root `rustup` folder, used for storing installed toolchains and
   configuration options.
 
-- `RUSTUP_TOOLCHAIN` (default: none) If set, will [override] the toolchain
-  used for all rust tool invocations. A toolchain with this name should be
-  installed, or invocations will fail.
+- `RUSTUP_TOOLCHAIN` (default: none) If set, will [override] the toolchain used
+  for all rust tool invocations. A toolchain with this name should be installed,
+  or invocations will fail. This can specify custom toolchains, installable
+  toolchains, or the absolute path to a toolchain.
 
 - `RUSTUP_DIST_SERVER` (default: `https://static.rust-lang.org`) Sets the root
   URL for downloading static resources related to Rust. You can change this to