Add named import syntax for ESM imports

README.md

@@ -117,6 +117,24 @@ bar = Bar.new
 bar.v4 => "b305f5c4-db9a-4504-b0c3-4e097a5ec8b9"
 ```
 
+### Named imports
+
+To import a specific named export from a package, use the `from:` syntax:
+
+```ruby
+class Bar < Nodo::Core
+  import :v4, from: 'uuid'
+
+  function :generate, <<~JS
+    () => {
+      return v4();
+    }
+  JS
+end
+```
+
+This is equivalent to `import { v4 } from 'uuid'` in JavaScript.
+
 ### Aliasing requires
 
 If the library name cannot be used as name of the constant, the `const` name

lib/nodo/core.rb

@@ -108,9 +108,16 @@ def finalize_context(context_id)
 
       { require: :cjs, import: :esm }.each do |method, type|
         define_method method do |*mods|
-          deps = mods.last.is_a?(Hash) ? mods.pop : {}
-          mods = mods.map { |m| [m, m] }.to_h
-          self.dependencies = dependencies + mods.merge(deps).map { |name, package| Dependency.new(name, package, type: type) }
+          opts = mods.last.is_a?(Hash) ? mods.pop : {}
+
+          if opts[:from] && mods.size == 1
+            name = mods.first
+            package = opts[:from]
+            self.dependencies = dependencies + [Dependency.new(name, package, type: type, named_export: name.to_s)]
+          else
+            mods = mods.map { |m| [m, m] }.to_h
+            self.dependencies = dependencies + mods.merge(opts).map { |name, package| Dependency.new(name, package, type: type) }
+          end
         end
         private method
       end

lib/nodo/dependency.rb

@@ -1,9 +1,9 @@
 module Nodo
   class Dependency
-    attr_reader :name, :package, :type
+    attr_reader :name, :package, :type, :named_export
 
-    def initialize(name, package, type:)
-      @name, @package, @type = name, package, type
+    def initialize(name, package, type:, named_export: nil)
+      @name, @package, @type, @named_export = name, package, type, named_export
     end
 
     def to_js
@@ -30,10 +30,11 @@ def to_cjs
     end
 
     def to_esm
+      extract = named_export ? "[#{named_export.to_json}]" : ""
       <<~JS
         const #{name} = __nodo_klass__.#{name} = await (async () => {
           try {
-            return await nodo.import(#{package.to_json});
+            return (await nodo.import(#{package.to_json}))#{extract};
           } catch(e) {
             e.nodo_dependency = #{package.to_json};
             throw e;

test/nodo_test.rb

@@ -8,7 +8,7 @@ def test_function
     end
     assert_equal 'Hello Nodo!', nodo.new.say_hi('Nodo')
   end
-  
+
   def test_require
     nodo = Class.new(Nodo::Core) do
       require :fs
@@ -17,7 +17,7 @@ def test_require
     assert_equal true, nodo.instance.exists_file(__FILE__)
     assert_equal false, nodo.instance.exists_file('FOOBARFOO')
   end
-  
+
   def test_require_npm
     nodo = Class.new(Nodo::Core) do
       require :uuid
@@ -26,23 +26,23 @@ def test_require_npm
     assert uuid = nodo.new.v4
     assert_equal 36, uuid.size
   end
-  
+
   def test_const
     nodo = Class.new(Nodo::Core) do
       const :FOOBAR, 123
       function :get_const, "() => FOOBAR"
     end
     assert_equal 123, nodo.new.get_const
   end
-  
+
   def test_script
     nodo = Class.new(Nodo::Core) do
       script "var somevar = 99;"
       function :get_somevar, "() => somevar"
     end
     assert_equal 99, nodo.new.get_somevar
   end
-  
+
   def test_deferred_script_definition_by_block
     nodo = Class.new(Nodo::Core) do
       singleton_class.attr_accessor :value
@@ -54,7 +54,7 @@ def test_deferred_script_definition_by_block
     nodo.value = 123
     assert_equal 123, nodo.new.get_somevar
   end
-  
+
   def test_cannot_define_both_code_and_block_for_script
     assert_raises ArgumentError do
       Class.new(Nodo::Core) do
@@ -64,14 +64,14 @@ def test_cannot_define_both_code_and_block_for_script
       end
     end
   end
-  
+
   def test_async_await
     nodo = Class.new(Nodo::Core) do
       function :do_something, "async () => { return await 'resolved'; }"
     end
     assert_equal 'resolved', nodo.new.do_something
   end
-  
+
   def test_inheritance
     klass = Class.new(Nodo::Core) do
       function :foo, "() => 'superclass'"
@@ -86,15 +86,15 @@ def test_inheritance
     assert_equal 'callingsuperclass', subclass.new.bar
     assert_equal 'callingsubsubclass', subsubclass.new.bar
   end
-  
+
   def test_class_function
     nodo = Class.new(Nodo::Core) do
       function :hello, "() => 'world'"
       class_function :hello
     end
     assert_equal 'world', nodo.hello
   end
-  
+
   def test_syntax
     nodo = Class.new(Nodo::Core) do
       function :test, timeout: nil, code: <<~'JS'
@@ -103,7 +103,7 @@ def test_syntax
     end
     assert_equal [1, 2, 3], nodo.new.test
   end
-  
+
   def test_deferred_function_definition_by_block
     nodo = lambda do
       Class.new(Nodo::Core) do
@@ -119,7 +119,7 @@ def test_deferred_function_definition_by_block
     assert_equal [1, nil, 3], nodo.().new.test
     assert_equal [1, 222, 3], nodo.().tap { |klass| klass.value = 222 }.new.test
   end
-  
+
   def test_cannot_define_both_code_and_block_for_function
     assert_raises ArgumentError do
       Class.new(Nodo::Core) do
@@ -129,7 +129,7 @@ def test_cannot_define_both_code_and_block_for_function
       end
     end
   end
-  
+
   def test_code_is_required
     assert_raises ArgumentError do
       Class.new(Nodo::Core) do
@@ -138,7 +138,7 @@ def test_code_is_required
       end
     end
   end
-  
+
   def test_timeout
     nodo = Class.new(Nodo::Core) do
       function :sleep, timeout: 1, code: <<~'JS'
@@ -149,15 +149,15 @@ def test_timeout
       nodo.new.sleep(2)
     end
   end
-  
+
   def test_internal_method_names_are_reserved
     assert_raises ArgumentError do
       Class.new(Nodo::Core) do
         function :tmpdir, code: "() => '.'"
       end
     end
   end
-  
+
   def test_logging
     with_logger test_logger do
       assert_raises(Nodo::JavaScriptError) do
@@ -178,25 +178,25 @@ def test_require_dependency_error
       end
     end
   end
-  
+
   def test_evaluation
     assert_equal 8, Class.new(Nodo::Core).new.evaluate('3 + 5')
   end
-  
+
   def test_evaluation_can_access_constants
     nodo = Class.new(Nodo::Core) do
       const :FOO, 'bar'
     end
     assert_equal 'barfoo', nodo.new.evaluate('FOO + "foo"')
   end
-  
+
   def test_evaluation_can_access_functions
     nodo = Class.new(Nodo::Core) do
       function :hello, code: "(name) => `Hello ${name}!`"
     end
     assert_equal 'Hello World!', nodo.new.evaluate('hello("World")')
   end
-  
+
   def test_evaluation_contexts_properties_are_shared_between_instances
     nodo = Class.new(Nodo::Core) do
       const :LIST, []
@@ -209,7 +209,7 @@ def test_evaluation_contexts_properties_are_shared_between_instances
     assert_equal %w[one two], one.evaluate('list()')
     assert_equal %w[one two], two.evaluate('list()')
   end
-  
+
   def test_evaluation_contexts_locals_are_separated_by_instance
     nodo = Class.new(Nodo::Core)
     one = nodo.new
@@ -219,26 +219,26 @@ def test_evaluation_contexts_locals_are_separated_by_instance
     assert_equal %w[one], one.evaluate('list')
     assert_equal %w[two], two.evaluate('list')
   end
-  
+
   def test_evaluation_can_require_on_its_own
     nodo = Class.new(Nodo::Core).new
     nodo.evaluate('const uuid = require("uuid")')
     uuid = nodo.evaluate('uuid.v4()')
     assert_uuid uuid
   end
-  
+
   def test_evaluation_can_access_requires
     nodo = Class.new(Nodo::Core) { require :uuid }
     uuid = nodo.new.evaluate('uuid.v4()')
     assert_uuid uuid
   end
-  
+
   def test_cannot_instantiate_core
     assert_raises Nodo::ClassError do
       Nodo::Core.new
     end
   end
-  
+
   def test_dynamic_imports_in_functions
     klass = Class.new(Nodo::Core) do
       function :v4, <<~JS
@@ -254,7 +254,7 @@ def self.name; "UUIDGen"; end
     assert_uuid uuid_2 = nodo.v4
     assert uuid_1 != uuid_2
   end
-  
+
   def test_dynamic_imports_in_evaluation
     nodo = Class.new(Nodo::Core)
     uuid = nodo.new.evaluate("nodo.import('uuid').then((uuid) => uuid.v4()).catch((e) => null)")
@@ -296,6 +296,43 @@ def test_evaluation_can_access_imports
     assert_uuid uuid
   end
 
+  def test_named_import
+    nodo = Class.new(Nodo::Core) do
+      import :v4, from: 'uuid'
+      function :generate, "() => v4()"
+    end
+
+    assert_uuid nodo.new.generate
+  end
+
+  def test_named_import_with_alias
+    nodo = Class.new(Nodo::Core) do
+      import :existsSync, from: 'fs'
+      function :exists_file, "(file) => existsSync(file)"
+    end
+
+    assert_equal true, nodo.instance.exists_file(__FILE__)
+    assert_equal false, nodo.instance.exists_file('FOOBARFOO')
+  end
+
+  def test_named_import_in_evaluation
+    nodo = Class.new(Nodo::Core) { import :v4, from: 'uuid' }
+    uuid = nodo.new.evaluate('v4()')
+    assert_uuid uuid
+  end
+
+  def test_named_import_dependency_error
+    with_logger nil do
+      nodo = Class.new(Nodo::Core) do
+        import :foo, from: 'nonexistent-package-12345'
+      end
+
+      assert_raises Nodo::DependencyError do
+        nodo.new
+      end
+    end
+  end
+
   private
 
   def test_logger
@@ -305,15 +342,15 @@ def error(msg); errors << msg; end
       self
     end
   end
-  
+
   def with_logger(logger)
     prev_logger = Nodo.logger
     Nodo.logger = logger
     yield
   ensure
     Nodo.logger = prev_logger
   end
-  
+
   def assert_uuid(obj)
     assert_match /\A\w{8}-\w{4}-\w{4}-\w{4}-\w{12}\z/, obj
   end