3 files changed, 22 insertions, 3 deletions
diff --git a/cli/deno_dir.rs b/cli/deno_dir.rs
index 645a053d0..3224fbf46 100644
--- a/cli/deno_dir.rs
+++ b/cli/deno_dir.rs
@@ -13,7 +13,7 @@ pub struct DenoDir {
 }
 
 impl DenoDir {
-  pub fn new(custom_root: Option<PathBuf>) -> std::io::Result<Self> {
+  pub fn new(maybe_custom_root: Option<PathBuf>) -> std::io::Result<Self> {
     // Only setup once.
     let home_dir = dirs::home_dir().expect("Could not get home directory.");
     let fallback = home_dir.join(".deno");
@@ -24,7 +24,16 @@ impl DenoDir {
       .map(|d| d.join("deno"))
       .unwrap_or(fallback);
 
-    let root: PathBuf = custom_root.unwrap_or(default);
+    let root: PathBuf = if let Some(root) = maybe_custom_root {
+      if root.is_absolute() {
+        root
+      } else {
+        std::env::current_dir()?.join(root)
+      }
+    } else {
+      default
+    };
+    assert!(root.is_absolute());
     let gen_path = root.join("gen");
 
     let deno_dir = Self {
diff --git a/cli/disk_cache.rs b/cli/disk_cache.rs
index f486e88af..828ca90ca 100644
--- a/cli/disk_cache.rs
+++ b/cli/disk_cache.rs
@@ -22,7 +22,9 @@ fn with_io_context<T: AsRef<str>>(
 }
 
 impl DiskCache {
+  /// `location` must be an absolute path.
   pub fn new(location: &Path) -> Self {
+    assert!(location.is_absolute());
     Self {
       location: location.to_owned(),
     }
@@ -211,7 +213,12 @@ mod tests {
 
   #[test]
   fn test_get_cache_filename_with_extension() {
-    let cache = DiskCache::new(&PathBuf::from("foo"));
+    let p = if cfg!(target_os = "windows") {
+      "C:\\foo"
+    } else {
+      "/foo"
+    };
+    let cache = DiskCache::new(&PathBuf::from(p));
 
     let mut test_cases = vec![
       (
diff --git a/cli/http_cache.rs b/cli/http_cache.rs
index 2771cb763..2a9882376 100644
--- a/cli/http_cache.rs
+++ b/cli/http_cache.rs
@@ -103,7 +103,10 @@ impl Metadata {
 
 impl HttpCache {
   /// Returns a new instance.
+  ///
+  /// `location` must be an absolute path.
   pub fn new(location: &Path) -> Self {
+    assert!(location.is_absolute());
     Self {
       location: location.to_owned(),
     }