Prevent kani crash during setup for first time (#2799)

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> 1. A description of how your changes improve Kani.
> 2. Some context on the problem you are solving.
> 3. A list of issues that are resolved by this PR.
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By using the `tar` file as a lock mechanism, we can detect incomplete
setups i.e when both `kani's` working directory and the tar file present
before setup, we can simply use the local bundle to start setup again.

Resolves #1545 

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 and MIT licenses.

src/lib.rs

@@ -16,11 +16,11 @@ mod cmd;
 mod os_hacks;
 mod setup;
 
-use std::env;
 use std::ffi::OsString;
 use std::os::unix::prelude::CommandExt;
 use std::path::{Path, PathBuf};
 use std::process::Command;
+use std::{env, fs};
 
 use anyhow::{bail, Context, Result};
 
@@ -33,6 +33,15 @@ pub fn proxy(bin: &str) -> Result<()> {
  fail_if_in_dev_environment()?;
  if !setup::appears_setup() {
  setup::setup(None)?;
+ } else {
+ // This handles cases where the setup was left incomplete due to an interrupt
+ // For example - https://github.com/model-checking/kani/issues/1545
+ if let Some(path_to_bundle) = setup::appears_incomplete() {
+ setup::setup(Some(path_to_bundle.clone().into_os_string()))?;
+ // Suppress warning with unused assignment
+ // and remove the bundle if it still exists
+ let _ = fs::remove_file(path_to_bundle);
+ }
  }
  exec(bin)
  }

src/setup.rs

@@ -53,6 +53,22 @@ pub fn appears_setup() -> bool {
  kani_dir().expect("couldn't find kani directory").exists()
 }
 
+// Ensure that the tar file does not exist, essentially using its presence
+// to detect setup completion as if it were a lock file.
+pub fn appears_incomplete() -> Option<PathBuf> {
+ let kani_dir = kani_dir().expect("couldn't find kani directory");
+ let kani_dir_parent = kani_dir.parent().unwrap();
+
+ for entry in std::fs::read_dir(&kani_dir_parent).ok()?.flatten() {
+ if let Some(file_name) = entry.file_name().to_str() {
+ if file_name.ends_with(".tar.gz") {
+ return Some(kani_dir_parent.join(file_name));
+ }
+ }
+ }
+ None
+}
+
 /// Sets up Kani by unpacking/installing to `~/.kani/kani-VERSION`
 pub fn setup(use_local_bundle: Option<OsString>) -> Result<()> {
  let kani_dir = kani_dir()?;
@@ -92,7 +108,10 @@ fn setup_kani_bundle(kani_dir: &Path, use_local_bundle: Option<OsString>) -> Res
  .arg("-zxf")
  .arg(&path)
  .current_dir(&kani_dir)
- .run()?;
+ .run()
+ .context(
+ "Failed to extract tar file, try removing Kani setup located in .kani in your home directory and restarting",
+ )?;
  } else {
  let filename = download_filename();
  println!("[2/5] Downloading Kani release bundle: {}", &filename);