fix: don't crash when $HOME is a relative path (#13581)

Absolutize the cache/home dir before use in DenoDir.

cli/deno_dir.rs

@@ -16,11 +16,7 @@ pub struct DenoDir {
 impl DenoDir {
   pub fn new(maybe_custom_root: Option<PathBuf>) -> std::io::Result<Self> {
     let root: PathBuf = if let Some(root) = maybe_custom_root {
-      if root.is_absolute() {
       root
-      } else {
-        std::env::current_dir()?.join(root)
-      }
     } else if let Some(cache_dir) = dirs::cache_dir() {
       // We use the OS cache dir because all files deno writes are cache files
       // Once that changes we need to start using different roots if DENO_DIR
@@ -32,6 +28,11 @@ impl DenoDir {
     } else {
       panic!("Could not set the Deno root directory")
     };
+    let root = if root.is_absolute() {
+      root
+    } else {
+      std::env::current_dir()?.join(root)
+    };
     assert!(root.is_absolute());
     let gen_path = root.join("gen");
 

cli/tests/integration/cache_tests.rs

@@ -48,3 +48,33 @@ itest!(ignore_require {
   output_str: Some(""),
   exit_code: 0,
 });
+
+// This test only runs on linux, because it hardcodes the XDG_CACHE_HOME env var
+// which is only used on linux.
+#[cfg(target_os = "linux")]
+#[test]
+fn relative_home_dir() {
+  use tempfile::TempDir;
+  use test_util as util;
+
+  let deno_dir = TempDir::new_in(util::testdata_path()).unwrap();
+  let path = deno_dir.path().strip_prefix(util::testdata_path()).unwrap();
+
+  let mut deno_cmd = util::deno_cmd();
+  let output = deno_cmd
+    .current_dir(util::testdata_path())
+    .env("XDG_CACHE_HOME", path)
+    .env_remove("HOME")
+    .env_remove("DENO_DIR")
+    .arg("cache")
+    .arg("--reload")
+    .arg("--no-check")
+    .arg("002_hello.ts")
+    .stdout(std::process::Stdio::piped())
+    .spawn()
+    .unwrap()
+    .wait_with_output()
+    .unwrap();
+  assert!(output.status.success());
+  assert_eq!(output.stdout, b"");
+}