[modules] Implement new syntax: export * as foo from "..."

This is behind a new flag --harmony-namespace-exports.

Bug: v8:8101
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: I9c252b6de2b08223fcf3296340b78d721471bdb4
Reviewed-on: https://chromium-review.googlesource.com/c/1258004
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56550}

src/bootstrapper.cc

@@ -4381,6 +4381,7 @@ void Bootstrapper::ExportFromRuntime(Isolate* isolate,
   void Genesis::InitializeGlobal_##id() {}
 
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_do_expressions)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_namespace_exports)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_public_fields)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_private_fields)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_static_fields)

src/flag-definitions.h

@@ -228,6 +228,8 @@ DEFINE_IMPLICATION(harmony_class_fields, harmony_private_fields)
 
 // Features that are complete (but still behind --harmony/es-staging flag).
 #define HARMONY_STAGED(V)                                                  \
+  V(harmony_namespace_exports,                                             \
+    "harmony namespace exports (export * as foo from 'bar')")              \
   V(harmony_public_fields, "harmony public fields in class literals")      \
   V(harmony_private_fields, "harmony private fields in class literals")    \
   V(harmony_numeric_separator, "harmony numeric separator between digits") \

src/parsing/parser.cc

@@ -1168,17 +1168,64 @@ Statement* Parser::ParseExportDefault(bool* ok) {
   return result;
 }
 
+const AstRawString* Parser::NextInternalNamespaceExportName() {
+  const char* prefix = ".ns-export";
+  std::string s(prefix);
+  s.append(std::to_string(number_of_named_namespace_exports_++));
+  return ast_value_factory()->GetOneByteString(s.c_str());
+}
+
+void Parser::ParseExportStar(bool* ok) {
+  int pos = position();
+  Consume(Token::MUL);
+
+  if (!FLAG_harmony_namespace_exports || !PeekContextualKeyword(Token::AS)) {
+    // 'export' '*' 'from' ModuleSpecifier ';'
+    Scanner::Location loc = scanner()->location();
+    ExpectContextualKeyword(Token::FROM, CHECK_OK_VOID);
+    Scanner::Location specifier_loc = scanner()->peek_location();
+    const AstRawString* module_specifier = ParseModuleSpecifier(CHECK_OK_VOID);
+    ExpectSemicolon(CHECK_OK_VOID);
+    module()->AddStarExport(module_specifier, loc, specifier_loc, zone());
+    return;
+  }
+  if (!FLAG_harmony_namespace_exports) return;
+
+  // 'export' '*' 'as' IdentifierName 'from' ModuleSpecifier ';'
+  //
+  // Desugaring:
+  //   export * as x from "...";
+  // ~>
+  //   import * as .x from "..."; export {.x as x};
+
+  ExpectContextualKeyword(Token::AS, CHECK_OK_VOID);
+  const AstRawString* export_name = ParseIdentifierName(CHECK_OK_VOID);
+  Scanner::Location export_name_loc = scanner()->location();
+  const AstRawString* local_name = NextInternalNamespaceExportName();
+  Scanner::Location local_name_loc = Scanner::Location::invalid();
+  DeclareVariable(local_name, VariableMode::kConst, kCreatedInitialized, pos,
+                  CHECK_OK_VOID);
+
+  ExpectContextualKeyword(Token::FROM, CHECK_OK_VOID);
+  Scanner::Location specifier_loc = scanner()->peek_location();
+  const AstRawString* module_specifier = ParseModuleSpecifier(CHECK_OK_VOID);
+  ExpectSemicolon(CHECK_OK_VOID);
+
+  module()->AddStarImport(local_name, module_specifier, local_name_loc,
+                          specifier_loc, zone());
+  module()->AddExport(local_name, export_name, export_name_loc, zone());
+}
+
 Statement* Parser::ParseExportDeclaration(bool* ok) {
   // ExportDeclaration:
   //    'export' '*' 'from' ModuleSpecifier ';'
+  //    'export' '*' 'as' IdentifierName 'from' ModuleSpecifier ';'
   //    'export' ExportClause ('from' ModuleSpecifier)? ';'
   //    'export' VariableStatement
   //    'export' Declaration
   //    'export' 'default' ... (handled in ParseExportDefault)
 
   Expect(Token::EXPORT, CHECK_OK);
-  int pos = position();
-
   Statement* result = nullptr;
   ZonePtrList<const AstRawString> names(1, zone());
   Scanner::Location loc = scanner()->peek_location();
@@ -1186,16 +1233,9 @@ Statement* Parser::ParseExportDeclaration(bool* ok) {
     case Token::DEFAULT:
       return ParseExportDefault(ok);
 
-    case Token::MUL: {
-      Consume(Token::MUL);
-      loc = scanner()->location();
-      ExpectContextualKeyword(Token::FROM, CHECK_OK);
-      Scanner::Location specifier_loc = scanner()->peek_location();
-      const AstRawString* module_specifier = ParseModuleSpecifier(CHECK_OK);
-      ExpectSemicolon(CHECK_OK);
-      module()->AddStarExport(module_specifier, loc, specifier_loc, zone());
-      return factory()->NewEmptyStatement(pos);
-    }
+    case Token::MUL:
+      ParseExportStar(CHECK_OK);
+      return factory()->NewEmptyStatement(position());
 
     case Token::LBRACE: {
       // There are two cases here:
@@ -1209,6 +1249,7 @@ Statement* Parser::ParseExportDeclaration(bool* ok) {
       // pass in a location that gets filled with the first reserved word
       // encountered, and then throw a SyntaxError if we are in the
       // non-FromClause case.
+      int pos = position();
       Scanner::Location reserved_loc = Scanner::Location::invalid();
       ZoneChunkList<ExportClauseData>* export_data =
           ParseExportClause(&reserved_loc, CHECK_OK);

src/parsing/parser.h

@@ -269,6 +269,7 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
   void ParseImportDeclaration(bool* ok);
   Statement* ParseExportDeclaration(bool* ok);
   Statement* ParseExportDefault(bool* ok);
+  void ParseExportStar(bool* ok);
   struct ExportClauseData {
     const AstRawString* export_name;
     const AstRawString* local_name;
@@ -1096,6 +1097,10 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
         node, new (zone()) TryFinallyStatementSourceRanges(body_range));
   }
 
+  // Generate the next internal variable name for binding an exported namespace
+  // object (used to implement the "export * as" syntax).
+  const AstRawString* NextInternalNamespaceExportName();
+
   // Parser's private field members.
   friend class PreParserZoneScope;  // Uses reusable_preparser().
 
@@ -1112,6 +1117,9 @@ class V8_EXPORT_PRIVATE Parser : public NON_EXPORTED_BASE(ParserBase<Parser>) {
 
   ScriptCompiler::CompileOptions compile_options_;
 
+  // For NextInternalNamespaceExportName().
+  int number_of_named_namespace_exports_ = 0;
+
   // Other information which will be stored in Parser and moved to Isolate after
   // parsing.
   int use_counts_[v8::Isolate::kUseCounterFeatureCount];

test/cctest/test-parsing.cc

@@ -6574,6 +6574,41 @@ TEST(BasicImportExportParsing) {
   }
 }
 
+TEST(NamespaceExportParsing) {
+  // clang-format off
+  const char* kSources[] = {
+      "export * as arguments from 'bar'",
+      "export * as await from 'bar'",
+      "export * as default from 'bar'",
+      "export * as enum from 'bar'",
+      "export * as foo from 'bar'",
+      "export * as for from 'bar'",
+      "export * as let from 'bar'",
+      "export * as static from 'bar'",
+      "export * as yield from 'bar'",
+  };
+  // clang-format on
+
+  i::FLAG_harmony_namespace_exports = true;
+  i::Isolate* isolate = CcTest::i_isolate();
+  i::Factory* factory = isolate->factory();
+
+  v8::HandleScope handles(CcTest::isolate());
+  v8::Local<v8::Context> context = v8::Context::New(CcTest::isolate());
+  v8::Context::Scope context_scope(context);
+
+  isolate->stack_guard()->SetStackLimit(i::GetCurrentStackPosition() -
+                                        128 * 1024);
+
+  for (unsigned i = 0; i < arraysize(kSources); ++i) {
+    i::Handle<i::String> source =
+        factory->NewStringFromAsciiChecked(kSources[i]);
+    i::Handle<i::Script> script = factory->NewScript(source);
+    i::ParseInfo info(isolate, script);
+    info.set_module();
+    CHECK(i::parsing::ParseProgram(&info, isolate));
+  }
+}
 
 TEST(ImportExportParsingErrors) {
   // clang-format off
@@ -6639,6 +6674,13 @@ TEST(ImportExportParsingErrors) {
       "import * as x, * as y from 'm.js';",
       "import {x}, {y} from 'm.js';",
       "import * as x, {y} from 'm.js';",
+
+      "export *;",
+      "export * as;",
+      "export * as foo;",
+      "export * as foo from;",
+      "export * as foo from ';",
+      "export * as ,foo from 'bar'",
   };
   // clang-format on
 

test/message/fail/modules-duplicate-export5.js

@@ -0,0 +1,9 @@
+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// MODULE
+// Flags: --harmony-namespace-exports
+
+export let foo = 42;
+export * as foo from "./doesnt-even-matter.js";

test/message/fail/modules-duplicate-export5.out

@@ -0,0 +1,5 @@
+*%(basename)s:9: SyntaxError: Duplicate export of 'foo'
+export * as foo from "./doesnt-even-matter.js";
+            ^^^
+SyntaxError: Duplicate export of 'foo'
+

test/mjsunit/harmony/modules-import-17.js

@@ -0,0 +1,11 @@
+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --harmony-namespace-exports
+
+var ns;
+import('modules-skip-13.js').then(x => ns = x);
+%RunMicrotasks();
+assertEquals(42, ns.default);
+assertEquals(ns, ns.self);

test/mjsunit/harmony/modules-skip-13.js

@@ -0,0 +1,6 @@
+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+export * as self from "./modules-skip-13.js";
+export default 42;

test/mjsunit/modules-export-star-as1.js

@@ -0,0 +1,10 @@
+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// MODULE
+// Flags: --harmony-namespace-exports
+
+import {foo} from "./modules-skip-8.js";
+assertEquals(42, foo.default);
+assertEquals(1, foo.get_a());

test/mjsunit/modules-export-star-as2.js

@@ -0,0 +1,19 @@
+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// MODULE
+// Flags: --harmony-namespace-exports
+
+export * as self from "./modules-export-star-as2.js";
+export * as self_again from "./modules-export-star-as2.js";
+import {self as myself} from "./modules-export-star-as2.js";
+import {self_again as myself_again} from "./modules-export-star-as2.js";
+
+assertEquals(["self", "self_again"], Object.keys(myself));
+assertEquals(myself, myself.self);
+assertEquals(myself_again, myself.self_again);
+assertEquals(myself, myself_again);
+
+assertThrows(_ => self, ReferenceError);
+assertThrows(_ => self_again, ReferenceError);

test/mjsunit/modules-export-star-as3.js

@@ -0,0 +1,15 @@
+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// MODULE
+// Flags: --harmony-namespace-exports
+
+let self = 42;
+export * as self from "./modules-export-star-as3.js";
+import {self as myself} from "./modules-export-star-as3.js";
+assertEquals(["self"], Object.keys(myself));
+assertEquals(myself, myself.self);
+assertEquals(42, self);
+self++;
+assertEquals(43, self);

test/mjsunit/modules-imports8.js

@@ -0,0 +1,11 @@
+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// MODULE
+// Flags: --harmony-namespace-exports
+
+import {a, b} from "./modules-skip-9.js";
+assertSame(a, b);
+assertEquals(42, a.default);
+assertEquals(1, a.a);

test/mjsunit/modules-skip-8.js

@@ -0,0 +1,5 @@
+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+export * as foo from "./modules-skip-1.js";

test/mjsunit/modules-skip-9.js

@@ -0,0 +1,7 @@
+// Copyright 2018 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import * as b from "./modules-skip-1.js";
+export {b};
+export * as a from "./modules-skip-1.js";

test/test262/testcfg.py

@@ -56,10 +56,10 @@ FEATURE_FLAGS = {
   'Symbol.prototype.description': '--harmony-symbol-description',
   'globalThis': '--harmony-global',
   'well-formed-json-stringify': '--harmony-json-stringify',
+  'export-star-as-namespace-from-module': '--harmony-namespace-exports',
 }
 
 SKIPPED_FEATURES = set(['Object.fromEntries',
-                        'export-star-as-namespace-from-module',
                         'class-fields-private',
                         'class-static-fields-private',
                         'class-methods-private',