Ensure that relative imports from module import are module-relative

Jint.Tests/Runtime/Modules/DefaultModuleLoaderTests.cs

@@ -21,6 +21,20 @@ public void ShouldResolveRelativePaths(string specifier, string expectedUri)
         Assert.Equal(SpecifierType.RelativeOrAbsolute, resolved.Type);
     }
 
+
+    [Fact]
+    public void ShouldResolveRelativeToReferencingModuleSpecifier()
+    {
+        var resolver = new DefaultModuleLoader("file:///project");
+
+        var resolved = resolver.Resolve("referencing-module", new ModuleRequest("./local-module-file.js", []));
+
+        Assert.Equal("./local-module-file.js", resolved.ModuleRequest.Specifier);
+        Assert.Equal("file:///project/referencing-module/local-module-file.js", resolved.Key);
+        Assert.Equal("file:///project/referencing-module/local-module-file.js", resolved.Uri?.AbsoluteUri);
+        Assert.Equal(SpecifierType.RelativeOrAbsolute, resolved.Type);
+    }
+
     [Theory]
     [InlineData("./../../other.js")]
     [InlineData("../../model/other.js")]

Jint/Runtime/Modules/DefaultModuleLoader.cs

@@ -116,7 +116,16 @@ Path traversal prevention is not a concern here because it is checked later
             */
             if (Uri.TryCreate(referencingModuleLocation, UriKind.Absolute, out var referencingLocation) ||
                 Uri.TryCreate(_basePath, referencingModuleLocation, out referencingLocation))
+            {
+                if (!Path.HasExtension(referencingLocation.LocalPath) && referencingLocation.LocalPath[^1] != '/')
+                {
+                    var uriBuilder = new UriBuilder(referencingLocation);
+                    uriBuilder.Path += '/';
+                    return uriBuilder.Uri;
+                }
+
                 return referencingLocation;
+            }
         }
         return _basePath;
     }