First prototype of import map generator.

utils/import_mapper/import_mapper.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#library('import_mapper');
+
+#import('dart:io');
+#import('../../client/json/dart_json.dart');

[Jennifer Messerly, 2012/02/09 01:09:24]

heh heh :)

[Bob Nystrom, 2012/02/09 02:05:44]

:)

+#import('../../frog/lang.dart');
+#import('../../frog/file_system.dart');
+#import('../../frog/file_system_vm.dart');
+
+typedef String ImportHook(ImportContext context, String name);
+
+/**
+ * Provides contextual information about the current import and environment
+ * that the import hook can use to resolve an import.
+ */
+class ImportContext {
+  // TODO(rnystrom): Fill in context here as we figure out what we want.
+}
+
+/** The generated import map. */
+Map<String, String> _importMap;
+
+ImportHook _hook;
+
+/**
+ * Uses the given import hook to generate an import map for all of the
+ * libraries used by a given entrypoint. The entrypoint is assumed to be
+ * provided as the first VM command line argument.
+ *
+ * Prints the import map data (a JSON object) to stdout.
+ */
+void generateImportMap(ImportHook hook) {
+  _hook = hook;
+
+  // Initialize frog.
+  final files = new VMFileSystem();
+  parseOptions('../../frog', ['', '', '--libdir=../../frog/lib'], files);
+  initializeWorld(files);
+  _importMap = {};
+
+  // The entrypoint of the library to generate an import map for.
+  final argv = (new Options()).arguments;
+  final entrypoint = argv[argv.length - 1];
+  _walkLibrary(entrypoint);
+
+  print(JSON.stringify(_importMap));
+}
+
+/**
+ * Recursively traverses all of the `#import()` directives in the given library
+ * entrypoint and runs the import hook on them. [entrypoint] should be a path
+ * to a library file.
+ */
+void _walkLibrary(String entrypoint) {
+  // TODO(rnystrom): Do more here when there's context we care about.
+  final context = new ImportContext();
+
+  final text = readFile(entrypoint);
+  final source = new SourceFile(entrypoint, text);
+  final parser = new Parser(source, true);

[Siggi Cherem (dart-lang), 2012/02/09 01:21:57]

=> Parser(source, diet: true);

[Bob Nystrom, 2012/02/09 02:05:44]

Done.

+
+  final definitions = parser.compilationUnit();
+
+  for (final definition in definitions) {
+    if (definition is DirectiveDefinition) {

[Jennifer Messerly, 2012/02/09 01:09:24]

perhaps:

if (definition is! DirectiveDefinition) break;

[Bob Nystrom, 2012/02/09 02:05:44]

Done.

+      DirectiveDefinition directive = definition;
+      if (directive.name.name == 'import') {
+        // The first argument is expected to be a string literal.
+        final name = directive.arguments[0].value.value.actualValue;
+
+        // Only map a given import once.
+        // TODO(rnystrom): Should invoke the hook again and ensure that it gets

[Jennifer Messerly, 2012/02/09 01:09:24]

maybe in debug mode, or something like that

[Bob Nystrom, 2012/02/09 02:05:44]

Agreed.

+        // the same result. It should be an error if the hook isn't
+        // referentially transparent.
+        if (!_importMap.containsKey(name)) {
+          final uri = _hook(context, name);
+          _importMap[name] = uri;
+
+          // Recurse into this library.
+          // TODO(rnystrom): Hackish. How should we handle corelib stuff?

[Siggi Cherem (dart-lang), 2012/02/09 01:21:57]

have a map file for corelibs and import mappings from there?

[Bob Nystrom, 2012/02/09 02:05:44]

The way this works is that the import hook *does* get a chance to handle
built-in libs. What we *don't* want to do is try to recursively walk *into*
those libs and traverse *their* imports because they may not have dart
implementations that we can parse.

+          if (!uri.startsWith('dart:')) {
+            _walkLibrary(_getFullPath(entrypoint, uri));
+          }
+        }
+      }
+    }
+  }
+}
+
+// TODO(rnystrom): Copied from frog/library.dart (makeFullPath).
+/**
+ * Given the path to a library containing an #import() and the resolved URI for
+ * that import, gives the full path to that library.
+ */
+String _getFullPath(String importingLibrary, String filename) {
+  if (filename.startsWith('dart:')) return filename;
+  // TODO(jmesserly): replace with node.js path.resolve
+  if (filename.startsWith('/')) return filename;
+  if (filename.startsWith('file:///')) return filename;
+  if (filename.startsWith('http://')) return filename;
+  if (const RegExp('^[a-zA-Z]:/').hasMatch(filename)) return filename;
+  return joinPaths(dirname(importingLibrary), filename);
+}
+
+String readFile(String filename) {
+  // TODO(rnystrom): There must be an easier way than this.
+  var file = (new File(filename)).openSync();
+  var length = file.lengthSync();
+  var buffer = new List<int>(length);
+  var bytes = file.readListSync(buffer, 0, length);
+  file.closeSync();
+  return new String.fromCharCodes(buffer);
+}