Fix sass/dart-sass-embedded#82

Author: ntkme

lib/sass/embedded/host.rb

@@ -3,6 +3,7 @@
 require_relative 'host/function_registry'
 require_relative 'host/importer_registry'
 require_relative 'host/logger_registry'
+require_relative 'host/no_op_importer'
 require_relative 'host/value_protofier'
 
 module Sass
@@ -54,7 +55,13 @@ def compile_request(path:,
                           source: source,
                           url: url&.to_s,
                           syntax: Protofier.to_proto_syntax(syntax),
-                          importer: importer.nil? ? nil : @importer_registry.register(importer)
+                          importer: if url && importer.nil?
+                                      EmbeddedProtocol::InboundMessage::CompileRequest::Importer.new(
+                                        path: File.absolute_path('.')
+                                      )
+                                    else
+                                      @importer_registry.register(importer.nil? ? NoOpImporter : importer)
+                                    end
                         )
                       end,
               path: path.nil? ? nil : File.absolute_path(path),

lib/sass/embedded/host/no_op_importer.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module Sass
+  class Embedded
+    class Host
+      # An importer that never imports any stylesheets.
+      module NoOpImporter
+        module_function
+
+        def canonicalize(*); end
+        def load(*); end
+      end
+
+      private_constant :NoOpImporter
+    end
+  end
+end