implement exports, fixes #141

R=vsm@google.com

Review URL: https://codereview.chromium.org/1263583005 .

Author: John Messerly

pkg/dev_compiler/lib/runtime/dart/_js_mirrors.js

@@ -118,7 +118,7 @@ dart_library.library('dart/_js_mirrors', null, /* Imports */[
         namedArgs = null;
       dart.assert(getName(constructorName) == "");
       dart.assert(namedArgs == null || dart.notNull(namedArgs.isEmpty));
-      let instance = exports._dart.instantiate(this[_cls], args);
+      let instance = new this[_cls](...args);
       return new JsInstanceMirror._(instance);
     }
   }

pkg/dev_compiler/lib/runtime/dart_runtime.js

@@ -64,7 +64,7 @@ dart_library.library('dart_runtime/dart', null, /* Imports */[
   ]);
 
   // From dart_utils
-  exportFrom(dart_utils, ['copyProperties', 'instantiate']);
+  exportFrom(dart_utils, ['copyProperties', 'export']);
   // Renames
   exports.defineLazyClass = _export(dart_utils.defineLazy);
   exports.defineLazyProperties = _export(dart_utils.defineLazy);

pkg/dev_compiler/lib/runtime/dart_utils.js

@@ -49,32 +49,32 @@ var dart_utils =
    * Defines a lazy property.
    * After initial get or set, it will replace itself with a value property.
    */
-  // TODO(jmesserly): is this the best implementation for JS engines?
   // TODO(jmesserly): reusing descriptor objects has been shown to improve
   // performance in other projects (e.g. webcomponents.js ShadowDOM polyfill).
   function defineLazyProperty(to, name, desc) {
     let init = desc.get;
-    let writable = !!desc.set;
-    function lazySetter(value) {
-      defineProperty(to, name, { value: value, writable: writable });
+    let value = null;
+
+    function lazySetter(x) {
+      init = null;
+      value = x;
+    }
+    function circularInitError() {
+      throwError('circular initialization for field ' + name);
     }
     function lazyGetter() {
-      // Clear the init function to detect circular initialization.
-      let f = init;
-      if (f === null) {
-        throwError('circular initialization for field ' + name);
-      }
-      init = null;
+      if (init == null) return value;
 
-      // Compute and store the value.
-      let value = f();
-      lazySetter(value);
+      // Compute and store the value, guarding against reentry.
+      let f = init;
+      init = circularInitError;
+      lazySetter(f());
       return value;
     }
     desc.get = lazyGetter;
     desc.configurable = true;
-    if (writable) desc.set = lazySetter;
-    defineProperty(to, name, desc);
+    if (desc.set) desc.set = lazySetter;
+    return defineProperty(to, name, desc);
   }
   dart_utils.defineLazyProperty = defineLazyProperty;
 
@@ -85,15 +85,8 @@ var dart_utils =
   }
   dart_utils.defineLazy = defineLazy;
 
-  function defineMemoizedGetter(obj, name, get) {
-    let cache = null;
-    function getter() {
-      if (cache != null) return cache;
-      cache = get();
-      get = null;
-      return cache;
-    }
-    defineProperty(obj, name, {get: getter, configurable: true});
+  function defineMemoizedGetter(obj, name, getter) {
+    return defineLazyProperty(obj, name, {get: getter});
   }
   dart_utils.defineMemoizedGetter = defineMemoizedGetter;
 
@@ -114,10 +107,17 @@ var dart_utils =
   }
   dart_utils.copyProperties = copyProperties;
 
-
-  function instantiate(type, args) {
-    return new type(...args);
+  /** Exports from one Dart module to another. */
+  function export_(to, from, show, hide) {
+    if (show == void 0) {
+      show = getOwnNamesAndSymbols(from);
+    }
+    if (hide != void 0) {
+      var hideMap = new Map(hide);
+      show = show.filter((k) => !hideMap.has(k));
+    }
+    return copyTheseProperties(to, from, show);
   }
-  dart_utils.instantiate = instantiate;
+  dart_utils.export = export_;
 
 })(dart_utils);

pkg/dev_compiler/lib/src/codegen/js_codegen.dart

@@ -13,6 +13,7 @@ import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/resolver.dart' show TypeProvider;
 import 'package:analyzer/src/generated/scanner.dart'
     show StringToken, Token, TokenType;
+import 'package:analyzer/src/task/dart.dart' show PublicNamespaceBuilder;
 
 import 'package:dev_compiler/src/codegen/ast_builder.dart' show AstBuilder;
 import 'package:dev_compiler/src/codegen/reify_coercions.dart'
@@ -95,6 +96,9 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
   /// _interceptors.JSArray<E>, used for List literals.
   ClassElement _jsArray;
 
+  /// The default value of the module object. See [visitLibraryDirective].
+  String _jsModuleValue;
+
   Map<String, DartType> _objectMembers;
 
   JSCodegenVisitor(AbstractCompiler compiler, this.currentLibrary,
@@ -115,42 +119,41 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
   TypeProvider get types => rules.provider;
 
   JS.Program emitLibrary(LibraryUnit library) {
-    String jsDefaultValue = null;
-
     // Modify the AST to make coercions explicit.
     new CoercionReifier(library, compiler).reify();
 
-    var unit = library.library;
-    if (unit.directives.isNotEmpty) {
-      var libraryDir = unit.directives.first;
-      if (libraryDir is LibraryDirective) {
-        var jsName = findAnnotation(libraryDir.element, _isJsNameAnnotation);
-        jsDefaultValue =
-            getConstantField(jsName, 'name', types.stringType) as String;
-      }
+    // Build the public namespace for this library. This allows us to do
+    // constant time lookups (contrast with `Element.getChild(name)`).
+    if (currentLibrary.publicNamespace == null) {
+      (currentLibrary as LibraryElementImpl).publicNamespace =
+          new PublicNamespaceBuilder().build(currentLibrary);
     }
 
-    // TODO(jmesserly): visit scriptTag, directives?
+    library.library.directives.forEach(_visit);
 
+    // Rather than directly visit declarations, we instead use [_loader] to
+    // visit them. It has the ability to sort elements on demand, so
+    // dependencies between top level items are handled with a minimal
+    // reordering of the user's input code. The loader will call back into
+    // this visitor via [_emitModuleItem] when it's ready to visit the item
+    // for real.
     _loader.collectElements(currentLibrary, library.partsThenLibrary);
 
     for (var unit in library.partsThenLibrary) {
       _constField = new ConstFieldVisitor(types, unit);
 
       for (var decl in unit.declarations) {
         if (decl is TopLevelVariableDeclaration) {
-          _visit(decl);
+          visitTopLevelVariableDeclaration(decl);
         } else {
           _loader.loadDeclaration(decl, decl.element);
         }
         if (decl is ClassDeclaration) {
           // Static fields can be emitted into the top-level code, so they need
           // to potentially be ordered independently of the class.
           for (var member in decl.members) {
-            if (member is FieldDeclaration && member.isStatic) {
-              for (var f in member.fields.variables) {
-                _loader.loadDeclaration(f, f.element);
-              }
+            if (member is FieldDeclaration) {
+              visitFieldDeclaration(member);
             }
           }
         }
@@ -208,19 +211,21 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
     var module = js.call("function(#) { 'use strict'; #; #; }",
         [params, dartxImport, _moduleItems]);
 
-    var program = <JS.Statement>[
-      js.statement("dart_library.library(#, #, #, #, #)", [
-        js.string(jsPath, "'"),
-        jsDefaultValue ?? new JS.LiteralNull(),
-        js.commentExpression(
-            "Imports", new JS.ArrayInitializer(imports, multiline: true)),
-        js.commentExpression("Lazy imports",
-            new JS.ArrayInitializer(lazyImports, multiline: true)),
-        module
-      ])
-    ];
+    var moduleDef = js.statement("dart_library.library(#, #, #, #, #)", [
+      js.string(jsPath, "'"),
+      _jsModuleValue ?? new JS.LiteralNull(),
+      js.commentExpression(
+          "Imports", new JS.ArrayInitializer(imports, multiline: true)),
+      js.commentExpression("Lazy imports",
+          new JS.ArrayInitializer(lazyImports, multiline: true)),
+      module
+    ]);
+
+    var jsBin = compiler.options.runnerOptions.v8Binary;
 
-    return new JS.Program(program);
+    String scriptTag = null;
+    if (library.library.scriptTag != null) scriptTag = '/usr/bin/env $jsBin';
+    return new JS.Program(<JS.Statement>[moduleDef], scriptTag: scriptTag);
   }
 
   void _emitModuleItem(AstNode node) {
@@ -232,6 +237,54 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
     if (code != null) _moduleItems.add(code);
   }
 
+  @override
+  void visitLibraryDirective(LibraryDirective node) {
+    assert(_jsModuleValue == null);
+
+    var jsName = findAnnotation(node.element, _isJsNameAnnotation);
+    _jsModuleValue =
+        getConstantField(jsName, 'name', types.stringType) as String;
+  }
+
+  @override
+  void visitImportDirective(ImportDirective node) {
+    // Nothing to do yet, but we'll want to convert this to an ES6 import once
+    // we have support for modules.
+  }
+
+  @override void visitPartDirective(PartDirective node) {}
+  @override void visitPartOfDirective(PartOfDirective node) {}
+
+  @override
+  void visitExportDirective(ExportDirective node) {
+    var exportName = _libraryName(node.uriElement);
+
+    var currentLibNames = currentLibrary.publicNamespace.definedNames;
+
+    var args = [_exportsVar, exportName];
+    if (node.combinators.isNotEmpty) {
+      var shownNames = <JS.Expression>[];
+      var hiddenNames = <JS.Expression>[];
+
+      var show = node.combinators.firstWhere((c) => c is ShowCombinator,
+          orElse: () => null) as ShowCombinator;
+      var hide = node.combinators.firstWhere((c) => c is HideCombinator,
+          orElse: () => null) as HideCombinator;
+      if (show != null) {
+        shownNames.addAll(show.shownNames
+            .map((i) => i.name)
+            .where((s) => !currentLibNames.containsKey(s))
+            .map((s) => js.string(s, "'")));
+      }
+      if (hide != null) {
+        hiddenNames.addAll(hide.hiddenNames.map((i) => js.string(i.name, "'")));
+      }
+      args.add(new JS.ArrayInitializer(shownNames));
+      args.add(new JS.ArrayInitializer(hiddenNames));
+    }
+    _moduleItems.add(js.statement('dart.export(#);', [args]));
+  }
+
   JS.Identifier _initSymbol(JS.Identifier id) {
     var s = js.statement('let # = $_SYMBOL(#);', [id, js.string(id.name, "'")]);
     _moduleItems.add(s);
@@ -1779,6 +1832,21 @@ class JSCodegenVisitor extends GeneralizingAstVisitor {
     }
   }
 
+  /// Emits static fields.
+  ///
+  /// Instance fields are emitted in [_initializeFields].
+  ///
+  /// These are generally treated the same as top-level fields, see
+  /// [visitTopLevelVariableDeclaration].
+  @override
+  visitFieldDeclaration(FieldDeclaration node) {
+    if (!node.isStatic) return;
+
+    for (var f in node.fields.variables) {
+      _loader.loadDeclaration(f, f.element);
+    }
+  }
+
   _addExport(String name) {
     if (!_exports.add(name)) throw 'Duplicate top level name found: $name';
   }

pkg/dev_compiler/lib/src/codegen/js_printer.dart

@@ -4,7 +4,7 @@
 
 library dev_compiler.src.codegen.js_printer;
 
-import 'dart:io' show Directory, File;
+import 'dart:io' show Directory, File, Platform, Process;
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:path/path.dart' as path;
 import 'package:source_maps/source_maps.dart' as srcmaps show Printer;
@@ -48,6 +48,12 @@ String writeJsLibrary(JS.Program jsTree, String outputPath,
     text = (context as JS.SimpleJavaScriptPrintingContext).getText();
   }
   new File(outputPath).writeAsStringSync(text);
+  if (jsTree.scriptTag != null) {
+    // Mark executable.
+    // TODO(jmesserly): should only do this if the input file was executable?
+    if (!Platform.isWindows) Process.runSync('chmod', ['+x', outputPath]);
+  }
+
   return computeHash(text);
 }
 

pkg/dev_compiler/lib/src/js/nodes.dart

@@ -245,8 +245,13 @@ abstract class Node {
 }
 
 class Program extends Node {
+  /// Script tag hash-bang, e.g. `#!/usr/bin/env node`
+  final String scriptTag;
+
+  /// Top-level statements in the program.
   final List<Statement> body;
-  Program(this.body);
+
+  Program(this.body, {this.scriptTag});
 
   accept(NodeVisitor visitor) => visitor.visitProgram(this);
   void visitChildren(NodeVisitor visitor) {

pkg/dev_compiler/lib/src/js/printer.dart

@@ -212,6 +212,9 @@ class Printer implements NodeVisitor {
   }
 
   visitProgram(Program program) {
+    if (program.scriptTag != null) {
+      out('#!${program.scriptTag}\n');
+    }
     visitAll(program.body);
   }
 

pkg/dev_compiler/test/browser/language_tests.js

@@ -68,4 +68,19 @@
       'asyncstar_yieldstar_test'
     ]);
   });
+
+  suite('export', () => {
+    dartLanguageTests([
+      'duplicate_export_test',
+      'export_cyclic_test',
+      'export_double_same_main_test',
+      'export_main_override_test',
+      'export_main_test',
+      'export_test',
+      'local_export_test',
+      'reexport_core_test',
+      'top_level_entry_test'
+    ]);
+  });
+
 })();

pkg/dev_compiler/test/codegen/expect/dir/html_input_b.js

@@ -1,8 +1,10 @@
 dart_library.library('dir/html_input_b', null, /* Imports */[
-  "dart_runtime/dart"
+  "dart_runtime/dart",
+  'dir/html_input_d'
 ], /* Lazy imports */[
-], function(exports, dart) {
+], function(exports, dart, html_input_d) {
   'use strict';
   let dartx = dart.dartx;
+  dart.export(exports, html_input_d);
   exports.x = 3;
 });

pkg/dev_compiler/test/codegen/expect/script.js

@@ -0,0 +1,18 @@
+#!/usr/bin/env iojs
+dart_library.library('script', null, /* Imports */[
+  "dart_runtime/dart",
+  'dart/core'
+], /* Lazy imports */[
+], function(exports, dart, core) {
+  'use strict';
+  let dartx = dart.dartx;
+  function main(args) {
+    let name = args[dartx.join](' ');
+    if (name == '')
+      name = 'world';
+    core.print(`hello ${name}`);
+  }
+  dart.fn(main, dart.void, [core.List$(core.String)]);
+  // Exports:
+  exports.main = main;
+});

pkg/dev_compiler/test/codegen/expect/script.txt

@@ -0,0 +1 @@
+// Messages from compiling script.dart