Allow custom path for installation/setup (rust-lang#2089)

Author: adpaco-aws

Diff for: .github/workflows/kani.yml

@@ -143,14 +143,15 @@ jobs:
         if: ${{ matrix.os == 'ubuntu-18.04' }}
         run: |
           docker build -t kani-20-04 -f scripts/ci/Dockerfile.bundle-test-ubuntu-20-04 .
+          docker build -t kani-20-04-alt -f scripts/ci/Dockerfile.bundle-test-ubuntu-20-04-alt .
           docker build -t kani-18-04 -f scripts/ci/Dockerfile.bundle-test-ubuntu-18-04 .
           # this one does its tests automatically, for reasons documented in the file:
           docker build -t kani-nixos -f scripts/ci/Dockerfile.bundle-test-nixos .
 
       - name: Run installed tests
         if: ${{ matrix.os == 'ubuntu-18.04' }}
         run: |
-          for tag in kani-20-04 kani-18-04; do
+          for tag in kani-20-04 kani-20-04-alt kani-18-04; do
             docker run $tag  cargo kani --version
             docker run -w /tmp/kani/tests/cargo-kani/simple-lib  $tag  cargo kani
             docker run -w /tmp/kani/tests/cargo-kani/simple-visualize  $tag  cargo kani

Diff for: scripts/ci/Dockerfile.bundle-test-ubuntu-20-04-alt

@@ -0,0 +1,22 @@
+# Copyright Kani Contributors
+# SPDX-License-Identifier: Apache-2.0 OR MIT
+
+# Note: this file is intended only for testing the kani release bundle
+# using an alternative install path *
+
+FROM ubuntu:20.04
+ENV DEBIAN_FRONTEND=noninteractive \
+    DEBCONF_NONINTERACTIVE_SEEN=true \
+    KANI_HOME="/tmp"
+RUN apt-get update && \
+    apt-get install -y python3 python3-pip curl ctags && \
+    curl -sSf https://sh.rustup.rs | sh -s -- -y
+ENV PATH="/root/.cargo/bin:${PATH}"
+
+WORKDIR /tmp/kani
+COPY ./tests ./tests
+COPY ./kani-latest-x86_64-unknown-linux-gnu.tar.gz ./
+# Very awkward glob (not regex!) to get `kani-verifier-*` and not `kani-verifier-*.crate`
+COPY ./target/package/kani-verifier-*[^e] ./kani-verifier
+RUN cargo install --path ./kani-verifier
+RUN cargo-kani setup --use-local-bundle ./kani-latest-x86_64-unknown-linux-gnu.tar.gz

Diff for: src/lib.rs

@@ -89,7 +89,7 @@ fn fail_if_in_dev_environment() -> Result<()> {
 /// Executes `kani-driver` in `bin` mode (kani or cargo-kani)
 /// augmenting environment variables to accomodate our release environment
 fn exec(bin: &str) -> Result<()> {
-    let kani_dir = setup::kani_dir();
+    let kani_dir = setup::kani_dir()?;
     let program = kani_dir.join("bin").join("kani-driver");
     let pyroot = kani_dir.join("pyroot");
     let bin_kani = kani_dir.join("bin");

Diff for: src/setup.rs

@@ -18,19 +18,44 @@ const VERSION: &str = env!("CARGO_PKG_VERSION");
 /// Set by our `build.rs`, reflects the Rust target triple we're building for
 const TARGET: &str = env!("TARGET");
 
-/// Where Kani has been installed. Typically `~/.kani/kani-1.x/`
-pub fn kani_dir() -> PathBuf {
-    home::home_dir().expect("Couldn't find home dir?").join(".kani").join(format!("kani-{VERSION}"))
+/// The directory where Kani is installed, either:
+///  * (custom) `${KANI_HOME}/kani-<VERSION>` if the environment variable
+///    `KANI_HOME` is set.
+///  * (default) `${HOME}/.kani/kani-<VERSION>` where `HOME` is the canonical
+///    definition of home directory used by Cargo and rustup.
+pub fn kani_dir() -> Result<PathBuf> {
+    let kani_dir = match env::var("KANI_HOME") {
+        Ok(val) => custom_kani_dir(val),
+        Err(_) => default_kani_dir()?,
+    };
+    let kani_dir = kani_dir.join(format!("kani-{VERSION}"));
+    Ok(kani_dir)
+}
+
+/// Returns the custom Kani home directory: `${KANI_HOME}`
+fn custom_kani_dir(path: String) -> PathBuf {
+    // We don't check if it doesn't exist since we create it later
+    PathBuf::from(path)
+}
+
+/// Returns the default Kani home directory: `${HOME}/.kani`
+fn default_kani_dir() -> Result<PathBuf> {
+    let home_dir = home::home_dir().expect("couldn't find home directory");
+    if !home_dir.is_dir() {
+        bail!("got home directory `{}` which isn't a directory", home_dir.display());
+    }
+    let kani_dir = home_dir.join(".kani");
+    Ok(kani_dir)
 }
 
 /// Fast check to see if we look setup already
 pub fn appears_setup() -> bool {
-    kani_dir().exists()
+    kani_dir().expect("couldn't find kani directory").exists()
 }
 
 /// Sets up Kani by unpacking/installing to `~/.kani/kani-VERSION`
 pub fn setup(use_local_bundle: Option<OsString>) -> Result<()> {
-    let kani_dir = kani_dir();
+    let kani_dir = kani_dir()?;
     let os = os_info::get();
 
     println!("[0/5] Running Kani first-time setup...");