1 files changed, 106 insertions, 0 deletions
diff --git a/crates/home/src/env.rs b/crates/home/src/env.rs
new file mode 100644
index 0000000..e47273b
--- /dev/null
+++ b/crates/home/src/env.rs
@@ -0,0 +1,106 @@
+//! Lower-level utilities for mocking the process environment.
+
+use std::{
+    ffi::OsString,
+    io,
+    path::{Path, PathBuf},
+};
+
+/// Permits parameterizing the home functions via the _from variants - used for
+/// in-process unit testing by rustup.
+pub trait Env {
+    /// Return the path to the the users home dir, or None if any error occurs:
+    /// see home_inner.
+    fn home_dir(&self) -> Option<PathBuf>;
+    /// Return the current working directory.
+    fn current_dir(&self) -> io::Result<PathBuf>;
+    /// Get an environment variable, as per std::env::var_os.
+    fn var_os(&self, key: &str) -> Option<OsString>;
+}
+
+/// Implements Env for the OS context, both Unix style and Windows.
+///
+/// This is trait permits in-process testing by providing a control point to
+/// allow in-process divergence on what is normally process wide state.
+///
+/// Implementations should be provided by whatever testing framework the caller
+/// is using. Code that is not performing in-process threaded testing requiring
+/// isolated rustup/cargo directories does not need this trait or the _from
+/// functions.
+pub struct OsEnv;
+impl Env for OsEnv {
+    fn home_dir(&self) -> Option<PathBuf> {
+        crate::home_dir_inner()
+    }
+    fn current_dir(&self) -> io::Result<PathBuf> {
+        std::env::current_dir()
+    }
+    fn var_os(&self, key: &str) -> Option<OsString> {
+        std::env::var_os(key)
+    }
+}
+
+pub const OS_ENV: OsEnv = OsEnv {};
+
+/// Returns the path of the current user's home directory from [`Env::home_dir`].
+pub fn home_dir_with_env(env: &dyn Env) -> Option<PathBuf> {
+    env.home_dir()
+}
+
+/// Variant of cargo_home where the environment source is parameterized. This is
+/// specifically to support in-process testing scenarios as environment
+/// variables and user home metadata are normally process global state. See the
+/// [`Env`] trait.
+pub fn cargo_home_with_env(env: &dyn Env) -> io::Result<PathBuf> {
+    let cwd = env.current_dir()?;
+    cargo_home_with_cwd_env(env, &cwd)
+}
+
+/// Variant of cargo_home_with_cwd where the environment source is
+/// parameterized. This is specifically to support in-process testing scenarios
+/// as environment variables and user home metadata are normally process global
+/// state. See the OsEnv trait.
+pub fn cargo_home_with_cwd_env(env: &dyn Env, cwd: &Path) -> io::Result<PathBuf> {
+    match env.var_os("CARGO_HOME").filter(|h| !h.is_empty()) {
+        Some(home) => {
+            let home = PathBuf::from(home);
+            if home.is_absolute() {
+                Ok(home)
+            } else {
+                Ok(cwd.join(&home))
+            }
+        }
+        _ => home_dir_with_env(env)
+            .map(|p| p.join(".cargo"))
+            .ok_or_else(|| io::Error::new(io::ErrorKind::Other, "could not find cargo home dir")),
+    }
+}
+
+/// Variant of cargo_home_with_cwd where the environment source is
+/// parameterized. This is specifically to support in-process testing scenarios
+/// as environment variables and user home metadata are normally process global
+/// state. See the OsEnv trait.
+pub fn rustup_home_with_env(env: &dyn Env) -> io::Result<PathBuf> {
+    let cwd = env.current_dir()?;
+    rustup_home_with_cwd_env(env, &cwd)
+}
+
+/// Variant of cargo_home_with_cwd where the environment source is
+/// parameterized. This is specifically to support in-process testing scenarios
+/// as environment variables and user home metadata are normally process global
+/// state. See the OsEnv trait.
+pub fn rustup_home_with_cwd_env(env: &dyn Env, cwd: &Path) -> io::Result<PathBuf> {
+    match env.var_os("RUSTUP_HOME").filter(|h| !h.is_empty()) {
+        Some(home) => {
+            let home = PathBuf::from(home);
+            if home.is_absolute() {
+                Ok(home)
+            } else {
+                Ok(cwd.join(&home))
+            }
+        }
+        _ => home_dir_with_env(env)
+            .map(|d| d.join(".rustup"))
+            .ok_or_else(|| io::Error::new(io::ErrorKind::Other, "could not find rustup home dir")),
+    }
+}