Adds facilities for extracting Intl.message calls and generating code from translations

pkg/intl/lib/extract_messages.dart

+// Copyright (c) 2013, 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.
+
+/**
+ * This is for use in extracting messages from a Dart program
+ * using the Intl.message() mechanism and writing them to a file for
+ * translation. This provides only the stub of a mechanism, because it
+ * doesn't define how the file should be written. It provides an
+ * [IntlMessage] class that holds the extracted data and [parseString]
+ * and [parseFile] methods which
+ * can extract messages that conform to the expected pattern:
+ *       (parameters) => Intl.message("Message $parameters", desc: ...);
+ * It uses the analyzer_experimental package to do the parsing, so may
+ * break if there are changes to the API that it provides.
+ * An example can be found in test/message_extraction/extract_to_json.dart
+ *
+ * Note that this does not understand how to follow part directives, so it
+ * has to explicitly be given all the files that it needs. A typical use case
+ * is to run it on all .dart files in a directory.
+ */
+library extract_messages;
+
+import 'package:analyzer_experimental/src/generated/ast.dart';
+import 'package:analyzer_experimental/src/generated/error.dart';
+import 'package:analyzer_experimental/src/generated/java_core.dart';
+import 'package:analyzer_experimental/src/generated/parser.dart';
+import 'package:analyzer_experimental/src/generated/scanner.dart';
+import 'package:analyzer_experimental/src/generated/source.dart';
+import 'package:analyzer_experimental/src/generated/utilities_dart.dart';
+import 'dart:io';
+import 'package:intl/src/intl_message.dart';
+
+/**
+ * Parse the dart program represented in [sourceCode] and return a Map from
+ * message names to [IntlMessage] instances. The [origin] is a string
+ * describing where the source came from, and is used in error messages.
+ */
+Map<String, IntlMessage> parseString(String sourceCode, [String origin]) {
+  var errorListener = new _ErrorCollector();
+  var scanner = new StringScanner(null, sourceCode, errorListener);
+  var token = scanner.tokenize();
+  var parser = new Parser(null, errorListener);
+  var unit = parser.parseCompilationUnit(token);
+  unit.lineInfo = new LineInfo(scanner.lineStarts);
+
+  var visitor = new MessageFindingVisitor(unit, origin);
+  unit.accept(visitor);
+  for (var error in errorListener.errors) {
+    print(error);
+  }
+  return visitor.messages;
+}
+
+/**
+ * Parse the source of the Dart program file [file] and return a Map from
+ * message names to [IntlMessage] instances.
+ */
+Map<String, IntlMessage> parseFile(File file) {
+  var sourceCode = file.readAsStringSync();
+  return parseString(sourceCode, file.path);
+}
+
+/**
+ * An error handler for parsing. Error handling is currently very primitive.
+ */
+class _ErrorCollector extends AnalysisErrorListener {
+  List<AnalysisError> errors;
+  _ErrorCollector() : errors = new List<AnalysisError>();
+  onError(error) => errors.add(error);
+}
+
+/**
+ * This visits the program source nodes looking for Intl.message uses
+ * that conform to its pattern and then finding the
+ */
+class MessageFindingVisitor extends GeneralizingASTVisitor {
+
+  /**
+   * The root of the compilation unit, and the first node we visit. We hold
+   * on to this for error reporting, as it can give us line numbers of other
+   * nodes.
+   */
+  final CompilationUnit root;
+
+  /**
+   * An arbitrary string describing where the source code came from. Most
+   * obviously, this could be a file path. We use this when reporting
+   * invalid messages.
+   */
+  final String origin;
+
+  MessageFindingVisitor(this.root, this.origin);
+
+  /**
+   * Accumulates the messages we have found.
+   */
+  final Map<String, IntlMessage> messages = new Map<String, IntlMessage>();
+
+  /**
+   * We keep track of the data from the last MethodDeclaration,
+   * FunctionDeclaration or FunctionExpression that we saw on the way down,
+   * as that will be the nearest parent of the Intl.message invocation.
+   */
+  FormalParameterList parameters;
+  String name;
+
+  /** Return true if [node] matches the pattern we expect for Intl.message() */
+  bool looksLikeIntlMessage(MethodInvocation node) {
+    if (node.methodName.name != "message") return false;
+    if (!(node.target is SimpleIdentifier)) return false;
+    SimpleIdentifier target = node.target;
+    if (target.token.toString() != "Intl") return false;
+    return true;
+  }
+
+  /**
+   * Returns a String describing why the node is invalid, or null if no
+   * reason is found, so it's presumed valid.
+   */
+  String checkValidity(MethodInvocation node) {
+    // The containing function cannot have named parameters.
+    if (parameters.parameters.any((each) => each.kind == ParameterKind.NAMED)) {
+      return "Named parameters on message functions are not supported.";
+    }
+    var arguments = node.argumentList.arguments;
+    if (!(arguments.first is StringLiteral)) {
+      return "Intl.message messages must be string literals";
+    }
+    var namedArguments = arguments.skip(1);
+    // This seems unlikely to happen, but make sure all are NamedExpression
+    // before doing the tests below.
+    if (!namedArguments.every((each) => each is NamedExpression)) {
+      return "Message arguments except the message must be named";
+    }
+    var notArgs = namedArguments.where(
+        (each) => each.name.label.name != 'args');
+    var values = notArgs.map((each) => each.expression).toList();
+    if (!values.every((each) => each is SimpleStringLiteral)) {
+      "Intl.message arguments must be simple string literals";
+    }
+    if (!notArgs.any((each) => each.name.label.name == 'name')) {
+      return "The 'name' argument for Intl.message must be specified";
+    }
+    var hasArgs = namedArguments.any((each) => each.name.label.name == 'args');
+    var hasParameters = !parameters.parameters.isEmpty;
+    if (!hasArgs && hasParameters) {
+      return "The 'args' argument for Intl.message must be specified";
+    }
+    return null;
+  }
+
+  /**
+   * Record the parameters of the function or method declaration we last
+   * encountered before seeing the Intl.message call.
+   */
+  void visitMethodDeclaration(MethodDeclaration node) {
+    parameters = node.parameters;
+    String name = node.name.name;
+    super.visitMethodDeclaration(node);
+  }
+
+  /**
+   * Record the parameters of the function or method declaration we last
+   * encountered before seeing the Intl.message call.
+   */
+  void visitFunctionExpression(FunctionExpression node) {
+    parameters = node.parameters;
+    name = null;
+    super.visitFunctionExpression(node);
+  }
+
+  /**
+   * Record the parameters of the function or method declaration we last
+   * encountered before seeing the Intl.message call.
+   */
+  void visitFunctionDeclaration(FunctionDeclaration node) {
+    parameters = node.functionExpression.parameters;
+    name = node.name.name;
+    super.visitFunctionDeclaration(node);
+  }
+
+  /**
+   * Examine method invocations to see if they look like calls to Intl.message.
+   */
+  void visitMethodInvocation(MethodInvocation node) {
+    addIntlMessage(node);
+    return super.visitNode(node);
+  }
+
+  /**
+   * Check that the node looks like an Intl.message invocation, and create
+   * the [IntlMessage] object from it and store it in [messages].
+   */
+  void addIntlMessage(MethodInvocation node) {
+    if (!looksLikeIntlMessage(node)) return;
+    var reason = checkValidity(node);
+    if (!(reason == null)) {
+      print("Skipping invalid Intl.message invocation\n    <$node>");
+      print("  reason: $reason");
+      reportErrorLocation(node);
+      return;
+    }
+    var message = messageFromMethodInvocation(node);
+    if (message != null) messages[message.name] = message;
+  }
+
+  /**
+   * Create an IntlMessage from [node] using the name and
+   * parameters of the last function/method declaration we encountered
+   * and the parameters to the Intl.message call.
+   */
+  IntlMessage messageFromMethodInvocation(MethodInvocation node) {
+    var message = new IntlMessage();
+    message.name = name;
+    message.arguments = parameters.parameters.elements.map(
+        (x) => x.identifier.name).toList();
+    try {
+      node.accept(new MessageVisitor(message));
+    } on IntlMessageExtractionException catch (e) {
+      message = null;
+      print("Error $e");
+      print("Processing <$node>");
+      reportErrorLocation(node);
+    }
+    return message;
+  }
+
+  void reportErrorLocation(ASTNode node) {
+    if (origin != null) print("from $origin");
+    LineInfo info = root.lineInfo;
+    if (info != null) {
+      LineInfo_Location line = info.getLocation(node.offset);
+      print("line: ${line.lineNumber}, column: ${line.columnNumber}");
+    }
+  }
+}
+
+/**
+ * Given a node that looks like an invocation of Intl.message, extract out
+ * the message and the parameters and store them in [target].
+ */
+class MessageVisitor extends GeneralizingASTVisitor {
+  IntlMessage target;
+
+  MessageVisitor(IntlMessage this.target);
+
+  /**
+   * Extract out the message string. If it's an interpolation, turn it into
+   * a single string with interpolation characters.
+   */
+  void visitArgumentList(ArgumentList node) {
+    var interpolation = new InterpolationVisitor(target);
+    node.arguments.elements.first.accept(interpolation);
+    target.messagePieces = interpolation.pieces;
+    super.visitArgumentList(node);
+  }
+
+  /**
+   * Find the values of all the named arguments, remove quotes, and save them
+   * into [target].
+   */
+  void visitNamedExpression(NamedExpression node) {
+    var name = node.name.label.name;
+    var exp = node.expression;
+    var string = exp is SimpleStringLiteral ? exp.value : exp.toString();
+    target[name] = string;
+    super.visitNamedExpression(node);
+  }
+}
+
+/**
+ * Given an interpolation, find all of its chunks, validate that they are only
+ * simple interpolations, and keep track of the chunks so that other parts
+ * of the program can deal with the interpolations and the simple string
+ * sections separately.
+ */
+class InterpolationVisitor extends GeneralizingASTVisitor {
+  IntlMessage message;
+
+  InterpolationVisitor(this.message);
+
+  List pieces = [];
+  String get extractedMessage => pieces.join();
+
+  void visitSimpleStringLiteral(SimpleStringLiteral node) {
+    pieces.add(node.value);
+    super.visitSimpleStringLiteral(node);
+  }
+
+  void visitInterpolationString(InterpolationString node) {
+    pieces.add(node.value);
+    super.visitInterpolationString(node);
+  }
+
+  // TODO(alanknight): The limitation to simple identifiers is important
+  // to avoid letting translators write arbitrary code, but is a problem
+  // for plurals.
+  void visitInterpolationExpression(InterpolationExpression node) {
+    if (node.expression is! SimpleIdentifier) {
+      throw new IntlMessageExtractionException(
+          "Only simple identifiers are allowed in message "
+          "interpolation expressions.\nError at $node");
+    }
+    var index = arguments.indexOf(node.expression.toString());
+    if (index == -1) {
+      throw new IntlMessageExtractionException(
+          "Cannot find argument ${node.expression}");
+    }
+    pieces.add(index);
+    super.visitInterpolationExpression(node);
+  }
+
+  List get arguments => message.arguments;
+}
+
+/**
+ * Exception thrown when we cannot process a message properly.
+ */
+class IntlMessageExtractionException implements Exception {
+  /**
+   * A message describing the error.
+   */
+  final String message;
+
+  /**
+   * Creates a new exception with an optional error [message].
+   */
+  const IntlMessageExtractionException([this.message = ""]);
+
+  String toString() => "IntlMessageExtractionException: $message";
+}