5 files changed, 81 insertions, 5 deletions
diff --git a/cli/npm/resolution/specifier.rs b/cli/npm/resolution/specifier.rs
index 1a1590a2f..b832540bd 100644
--- a/cli/npm/resolution/specifier.rs
+++ b/cli/npm/resolution/specifier.rs
@@ -32,8 +32,12 @@ impl NpmPackageReference {
   }
 
   pub fn from_str(specifier: &str) -> Result<NpmPackageReference, AnyError> {
+    let original_text = specifier;
     let specifier = match specifier.strip_prefix("npm:") {
-      Some(s) => s,
+      Some(s) => {
+        // Strip leading slash, which might come from import map
+        s.strip_prefix('/').unwrap_or(s)
+      }
       None => {
         // don't allocate a string here and instead use a static string
         // because this is hit a lot when a url is not an npm specifier
@@ -65,7 +69,12 @@ impl NpmPackageReference {
     let sub_path = if parts.len() == name_parts.len() {
       None
     } else {
-      Some(parts[name_part_len..].join("/"))
+      let sub_path = parts[name_part_len..].join("/");
+      if sub_path.is_empty() {
+        None
+      } else {
+        Some(sub_path)
+      }
     };
 
     if let Some(sub_path) = &sub_path {
@@ -79,6 +88,14 @@ impl NpmPackageReference {
       }
     }
 
+    if name.is_empty() {
+      let msg = format!(
+        "Invalid npm specifier '{}'. Did not contain a package name.",
+        original_text
+      );
+      return Err(generic_error(msg));
+    }
+
     Ok(NpmPackageReference {
       req: NpmPackageReq { name, version_req },
       sub_path,
@@ -631,6 +648,54 @@ mod tests {
         .to_string(),
       "Not a valid package: @package"
     );
+
+    // should parse leading slash
+    assert_eq!(
+      NpmPackageReference::from_str("npm:/@package/test/sub_path").unwrap(),
+      NpmPackageReference {
+        req: NpmPackageReq {
+          name: "@package/test".to_string(),
+          version_req: None,
+        },
+        sub_path: Some("sub_path".to_string()),
+      }
+    );
+    assert_eq!(
+      NpmPackageReference::from_str("npm:/test").unwrap(),
+      NpmPackageReference {
+        req: NpmPackageReq {
+          name: "test".to_string(),
+          version_req: None,
+        },
+        sub_path: None,
+      }
+    );
+    assert_eq!(
+      NpmPackageReference::from_str("npm:/test/").unwrap(),
+      NpmPackageReference {
+        req: NpmPackageReq {
+          name: "test".to_string(),
+          version_req: None,
+        },
+        sub_path: None,
+      }
+    );
+
+    // should error for no name
+    assert_eq!(
+      NpmPackageReference::from_str("npm:/")
+        .err()
+        .unwrap()
+        .to_string(),
+      "Invalid npm specifier 'npm:/'. Did not contain a package name."
+    );
+    assert_eq!(
+      NpmPackageReference::from_str("npm://test")
+        .err()
+        .unwrap()
+        .to_string(),
+      "Invalid npm specifier 'npm://test'. Did not contain a package name."
+    );
   }
 
   #[test]
diff --git a/cli/tests/testdata/npm/import_map/import_map.json b/cli/tests/testdata/npm/import_map/import_map.json
index a7ed13b82..1c3baacd1 100644
--- a/cli/tests/testdata/npm/import_map/import_map.json
+++ b/cli/tests/testdata/npm/import_map/import_map.json
@@ -1,5 +1,6 @@
 {
   "imports": {
-    "chalk": "npm:chalk@5"
+    "chalk": "npm:chalk@5",
+    "@denotest/": "npm:/@denotest/dual-cjs-esm/"
   }
 }
diff --git a/cli/tests/testdata/npm/import_map/main.js b/cli/tests/testdata/npm/import_map/main.js
index fe7ef549a..e354b7e92 100644
--- a/cli/tests/testdata/npm/import_map/main.js
+++ b/cli/tests/testdata/npm/import_map/main.js
@@ -1,7 +1,10 @@
 import chalk from "chalk";
+import { getSubPathKind } from "@denotest/subpath/main.mjs";
 
 console.log(chalk.green("chalk import map loads"));
 
 export function test(value) {
   return chalk.red(value);
 }
+
+console.log(getSubPathKind());
diff --git a/cli/tests/testdata/npm/import_map/main.out b/cli/tests/testdata/npm/import_map/main.out
index ef3f4e22b..b5b67651e 100644
--- a/cli/tests/testdata/npm/import_map/main.out
+++ b/cli/tests/testdata/npm/import_map/main.out
@@ -1,3 +1,6 @@
+Download http://localhost:4545/npm/registry/@denotest/dual-cjs-esm
 Download http://localhost:4545/npm/registry/chalk
+Download http://localhost:4545/npm/registry/@denotest/dual-cjs-esm/1.0.0.tgz
 Download http://localhost:4545/npm/registry/chalk/chalk-5.0.1.tgz
 chalk import map loads
+esm
diff --git a/cli/tsc/00_typescript.js b/cli/tsc/00_typescript.js
index 01377c8b5..4f2a0c467 100644
--- a/cli/tsc/00_typescript.js
+++ b/cli/tsc/00_typescript.js
@@ -90846,7 +90846,7 @@ var ts;
             if (!text.startsWith("npm:")) {
                 throw new Error("Not an npm specifier: ".concat(text));
             }
-            text = text.replace(/^npm:/, "");
+            text = text.replace(/^npm:\/?/, "");
             var parts = text.split("/");
             var namePartLen = text.startsWith("@") ? 2 : 1;
             if (parts.length < namePartLen) {
@@ -90860,8 +90860,12 @@ var ts;
                 versionReq = lastNamePart.substring(lastAtIndex + 1);
                 nameParts[nameParts.length - 1] = lastNamePart.substring(0, lastAtIndex);
             }
+            var name = nameParts.join("/");
+            if (name.length === 0) {
+                throw new Error("Npm specifier did not have a name: ".concat(text));
+            }
             return {
-                name: nameParts.join("/"),
+                name: name,
                 versionReq: versionReq,
                 subPath: parts.length > nameParts.length ? parts.slice(nameParts.length).join("/") : undefined,
             };