[Bun.build] Add error when an `onResolve` plugin returns a `namespace` which has no loader

1 files changed, 7 insertions, 0 deletions

diff --git a/src/bun.js/builtins/js/BundlerPlugin.js b/src/bun.js/builtins/js/BundlerPlugin.js
index f580a1c05..64c655bbe 100644
--- a/src/bun.js/builtins/js/BundlerPlugin.js
+++ b/src/bun.js/builtins/js/BundlerPlugin.js
@@ -136,6 +136,13 @@ function runOnResolvePlugins(
               );
             }
           }
+
+          if (userNamespace && userNamespace !== "file" && (!onLoad || !onLoad.@has(userNamespace))) {
+            @throwTypeError(
+              `Expected onLoad plugin for namespace ${@jsonStringify(userNamespace, " ")} to exist`
+            );
+          }
+
         }
         this.onResolveAsync(internalID, path, userNamespace, external);
         return null;