Add JavaScript AST.

lib/compiler/implementation/js/printer.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.
+
+class Printer implements NodeVisitor {
+  final bool shouldCompressOutput = false;
+  leg.Compiler compiler;
+  var positionElement;
+  leg.CodeBuffer outBuffer;
+  int indentLevel = 0;
+  bool inForInit = false;
+  bool atStatementBegin = false;
+
+  Printer(this.compiler, this.positionElement)
+      : outBuffer = new leg.CodeBuffer();
+
+  void spaceOut() {
+    if (!shouldCompressOutput) out(" ");
+  }
+  void lineOut() {
+    if (!shouldCompressOutput) out("\n");
+  }
+
+  String lastAddedString = null;
+  int get lastCharCode() {
+    if (lastAddedString == null) return 0;
+    assert(lastAddedString.length != "");
+    return lastAddedString.charCodeAt(lastAddedString.length - 1);
+  }
+
+  void out(String str) {
+    if (str != "") {
+      outBuffer.add(str);
+      lastAddedString = str;
+    }
+  }
+  void outLn(String str) {
+    out(str);
+    lineOut();
+  }
+  void outIndent(String str) { indent(); out(str); }
+  void outIndentLn(String str) { indent(); outLn(str); }
+  void indent() {
+    if (!shouldCompressOutput) {
+      for (int i = 0; i < indentLevel; i++) out("  ");
+    }
+  }
+
+  void recordSourcePosition(var position) {
+    if (position != null) {
+      outBuffer.setSourceLocation(positionElement, position);
+    }
+  }
+
+  visit(Node node) {
+    recordSourcePosition(node.sourcePosition);
+    node.accept(this);
+    recordSourcePosition(node.endSourcePosition);
+  }
+
+  visitCommaSeparated(List<Node> nodes, int hasRequiredType,
+                      [bool newInForInit, bool newAtStatementBegin]) {
+    for (int i = 0; i < nodes.length; i++) {
+      if (i != 0) {
+        atStatementBegin = false;
+        out(",");
+        spaceOut();
+      }
+      visitNestedExpression(nodes[i], hasRequiredType,
+                            newInForInit, newAtStatementBegin);
+    }
+  }
+
+  visitAll(List<Node> nodes) {
+    nodes.forEach(visit);
+  }
+
+  visitProgram(Program program) {
+    visitAll(program.body);
+  }
+
+  bool blockBody(Node body, [bool needsSeparation, bool needsNewline]) {
+    if (body is Block) {
+      spaceOut();
+      blockOut(body, false, needsNewline);
+      return true;
+    }
+    if (shouldCompressOutput && needsSeparation) {
+      // If [shouldCompressOutput] is false, then the 'lineOut' will insert
+      // the separation.
+      out(" ");
+    } else {
+      lineOut();
+    }
+    indentLevel++;
+    visit(body);
+    indentLevel--;
+    return false;
+  }
+
+  void blockOutWithoutBraces(Node node) {
+    if (node is Block) {
+      node.statements.forEach(blockOutWithoutBraces);
+    } else {
+      visit(node);
+    }
+  }
+
+  void blockOut(Block node, bool shouldIndent, bool needsNewline) {
+    if (shouldIndent) indent();
+    out("{");
+    lineOut();
+    indentLevel++;
+    node.statements.forEach(blockOutWithoutBraces);
+    indentLevel--;
+    indent();
+    out("}");
+    if (needsNewline) lineOut();
+  }
+
+  visitBlock(Block block) {
+    blockOut(block, true, true);
+  }
+
+  visitExpressionStatement(ExpressionStatement expressionStatement) {
+    indent();
+    visitNestedExpression(expressionStatement.expression, EXPRESSION,
+                          newInForInit: false, newAtStatementBegin: true);
+    outLn(";");
+  }
+
+  visitEmptyStatement(EmptyStatement nop) {
+    outIndentLn(";");
+  }
+
+  void ifOut(If node, bool shouldIndent) {
+    Node then = node.then;
+    Node elsePart = node.otherwise;
+    bool hasElse = node.hasElse;
+    // Handle dangling elses.
+    // If the then-branch is an if, which has no else-branch, but we do
+    // have one, then we need to put the nested if into braces.
+    if (hasElse && then is If) {
+      Node nested = then;
+      do {
+        If nestedIf = nested;
+        if (!nestedIf.hasElse) {
+          then = new Block(<Statement>[then]);
+          break;
+        }
+        nested = nestedIf.otherwise;
+      } while (nested is If);
+    }
+    if (then is If && !(then as If).hasElse && hasElse) {
+      then = new Block(<Statement>[then]);
+    }
+    if (shouldIndent) indent();
+    out("if");
+    spaceOut();
+    out("(");
+    visitNestedExpression(node.condition, EXPRESSION,
+                          newInForInit: false, newAtStatementBegin: false);
+    out(")");
+    bool thenWasBlock =
+        blockBody(then, needsSeparation: false, needsNewline: !hasElse);
+    if (hasElse) {
+      if (thenWasBlock) {
+        spaceOut();
+      } else {
+        indent();
+      }
+      out("else");
+      if (elsePart is If) {
+        out(" ");
+        ifOut(elsePart, false);
+      } else {
+        blockBody(elsePart, needsSeparation: true, needsNewline: true);
+      }
+    }
+  }
+
+  visitIf(If node) {
+    ifOut(node, true);
+  }
+
+  visitFor(For loop) {
+    outIndent("for");
+    spaceOut();
+    out("(");
+    if (loop.init !== null) {
+      visitNestedExpression(loop.init, EXPRESSION,
+                            newInForInit: true, newAtStatementBegin: false);
+    }
+    out(";");
+    if (loop.condition !== null) {
+      spaceOut();
+      visitNestedExpression(loop.condition, EXPRESSION,
+                            newInForInit: false, newAtStatementBegin: false);
+    }
+    out(";");
+    if (loop.update !== null) {
+      spaceOut();
+      visitNestedExpression(loop.update, EXPRESSION,
+                            newInForInit: false, newAtStatementBegin: false);
+    }
+    out(")");
+    blockBody(loop.body, needsSeparation: false, needsNewline: true);
+  }
+
+  visitForIn(ForIn loop) {
+    outIndent("for");
+    spaceOut();
+    out("(");
+    visitNestedExpression(loop.leftHandSide, EXPRESSION,
+                          newInForInit: true, newAtStatementBegin: false);
+    out(" in ");
+    visitNestedExpression(loop.object, EXPRESSION,
+                          newInForInit: false, newAtStatementBegin: false);
+    out(")");
+    blockBody(loop.body, needsSeparation: false, needsNewline: true);
+  }
+
+  visitWhile(While loop) {
+    outIndent("while");
+    spaceOut();
+    out("(");
+    visitNestedExpression(loop.condition, EXPRESSION,
+                          newInForInit: false, newAtStatementBegin: false);
+    out(")");
+    blockBody(loop.body, needsSeparation: false, needsNewline: true);
+  }
+
+  visitDo(Do loop) {
+    outIndent("do");
+    if (blockBody(loop.body, needsSeparation: true, needsNewline: false)) {
+      spaceOut();
+    } else {
+      indent();
+    }
+    out("while");
+    spaceOut();
+    out("(");
+    visitNestedExpression(loop.condition, EXPRESSION,
+                          newInForInit: false, newAtStatementBegin: false);
+    outLn(");");
+  }
+
+  visitContinue(Continue node) {
+    if (node.targetLabel == null) {
+      outIndentLn("continue;");
+    } else {
+      outIndentLn("continue ${node.targetLabel};");
+    }
+  }
+
+  visitBreak(Break node) {
+    if (node.targetLabel == null) {
+      outIndentLn("break;");
+    } else {
+      outIndentLn("break ${node.targetLabel};");
+    }
+  }
+
+  visitReturn(Return node) {
+    if (node.value == null) {
+      outIndentLn("return;");
+    } else {
+      outIndent("return ");
+      visitNestedExpression(node.value, EXPRESSION,
+                            newInForInit: false, newAtStatementBegin: false);
+      outLn(";");
+    }
+  }
+
+  visitThrow(Throw node) {
+    outIndent("throw ");
+    visitNestedExpression(node.expression, EXPRESSION,
+                          newInForInit: false, newAtStatementBegin: false);
+    outLn(";");
+  }
+
+  visitTry(Try node) {
+    outIndent("try");
+    blockBody(node.body, needsSeparation: true, needsNewline: false);
+    spaceOut();
+    if (node.catchPart !== null) {
+      visit(node.catchPart);
+    }
+    if (node.finallyPart !== null) {
+      spaceOut();
+      out("finally");
+      blockBody(node.finallyPart, needsSeparation: true, needsNewline: true);
+    } else {
+      lineOut();
+    }
+  }
+
+  visitCatch(Catch node) {
+    spaceOut();
+    out("catch");
+    spaceOut();
+    out("(");
+    visitNestedExpression(node.declaration, EXPRESSION,
+                          newInForInit: false, newAtStatementBegin: false);
+    out(")");
+    blockBody(node.body, needsSeparation: false, needsNewline: true);
+  }
+
+  visitSwitch(Switch node) {
+    outIndent("switch");
+    spaceOut();
+    out("(");
+    visitNestedExpression(node.key, EXPRESSION,
+                          newInForInit: false, newAtStatementBegin: false);
+    out(")");
+    spaceOut();
+    outLn("{");
+    indentLevel++;
+    visitAll(node.cases);
+    indentLevel--;
+    outIndentLn("}");
+  }
+
+  visitCase(Case node) {
+    outIndent("case ");
+    visitNestedExpression(node.expression, EXPRESSION,
+                          newInForInit: false, newAtStatementBegin: false);
+    outLn(":");
+    if (!node.body.statements.isEmpty()) {
+      indentLevel++;
+      blockOutWithoutBraces(node.body);
+      indentLevel--;
+    }
+  }
+
+  visitDefault(Default node) {
+    outIndentLn("default:");
+    if (!node.body.statements.isEmpty()) {
+      indentLevel++;
+      blockOutWithoutBraces(node.body);
+      indentLevel--;
+    }
+  }
+
+  visitLabeledStatement(LabeledStatement node) {
+    outIndent("${node.label}:");
+    blockBody(node.body, needsSeparation: false, needsNewline: true);
+  }
+
+  void functionOut(Fun fun, Node name) {
+    out("function");
+    if (name != null) {
+      out(" ");
+      // Name must be a [Decl]. Therefore only test for primary expressions.
+      visitNestedExpression(name, PRIMARY,
+                            newInForInit: false, newAtStatementBegin: false);
+    }
+    out("(");
+    if (fun.params != null) {
+      visitCommaSeparated(fun.params, PRIMARY,
+                          newInForInit: false, newAtStatementBegin: false);
+    }
+    out(")");
+    blockBody(fun.body, needsSeparation: false, needsNewline: false);
+  }
+
+  visitFunctionDeclaration(FunctionDeclaration declaration) {
+    indent();
+    functionOut(declaration.function, declaration.name);
+    lineOut();
+  }
+
+  visitNestedExpression(Expression node, int requiredPrecedence,
+                        [bool newInForInit, bool newAtStatementBegin]) {
+    bool needsParentheses =
+        // a - (b + c).
+        (requiredPrecedence != EXPRESSION &&
+         node.precedenceLevel < requiredPrecedence) ||
+        // for (a = (x in o); ... ; ... ) { ... }
+        (newInForInit && node is Binary && (node as Binary).op == "in") ||
+        // (function() { ... })().
+        // ({a: 2, b: 3}.toString()).
+        (newAtStatementBegin && (node is NamedFunction ||
+                                 node is Fun ||
+                                 node is ObjectInitializer));
+    if (needsParentheses) {
+      inForInit = false;
+      atStatementBegin = false;
+      out("(");
+      visit(node);
+      out(")");
+    } else {
+      inForInit = newInForInit;
+      atStatementBegin = newAtStatementBegin;
+      visit(node);
+    }
+  }
+
+  visitVariableDeclarationList(VariableDeclarationList list) {
+    out("var ");
+    visitCommaSeparated(list.declarations, ASSIGNMENT,
+                        newInForInit: inForInit, newAtStatementBegin: false);
+  }
+
+  visitSequence(Sequence sequence) {
+    // Note that we only require that the entries are expressions and not
+    // assignments. This means that nested sequences are not put into
+    // parenthesis.
+    visitCommaSeparated(sequence.expressions, EXPRESSION,
+                        newInForInit: false,
+                        newAtStatementBegin: atStatementBegin);
+  }
+
+  visitAssignment(Assignment assignment) {
+    visitNestedExpression(assignment.leftHandSide, LEFT_HAND_SIDE,
+                          newInForInit: inForInit,
+                          newAtStatementBegin: atStatementBegin);
+    if (assignment.value !== null) {
+      spaceOut();
+      String op = assignment.op;
+      if (op != null) out(op);
+      out("=");
+      spaceOut();
+      visitNestedExpression(assignment.value, ASSIGNMENT,
+                            newInForInit: inForInit,
+                            newAtStatementBegin: false);
+    }
+  }
+
+  visitVariableInitialization(VariableInitialization initialization) {
+    visitAssignment(initialization);
+  }
+
+  visitConditional(Conditional cond) {
+    visitNestedExpression(cond.condition, LOGICAL_OR,
+                          newInForInit: inForInit,
+                          newAtStatementBegin: atStatementBegin);
+    spaceOut();
+    out("?");
+    spaceOut();
+    // The then part is allowed to have an 'in'.
+    visitNestedExpression(cond.then, ASSIGNMENT,
+                          newInForInit: false, newAtStatementBegin: false);
+    spaceOut();
+    out(":");
+    spaceOut();
+    visitNestedExpression(cond.otherwise, ASSIGNMENT,
+                          newInForInit: inForInit, newAtStatementBegin: false);
+  }
+
+  visitNew(New node) {
+    out("new ");
+    visitNestedExpression(node.target, CALL,
+                          newInForInit: inForInit, newAtStatementBegin: false);
+    out("(");
+    visitCommaSeparated(node.arguments, ASSIGNMENT,
+                        newInForInit: false, newAtStatementBegin: false);
+    out(")");
+  }
+
+  visitCall(Call call) {
+    visitNestedExpression(call.target, LEFT_HAND_SIDE,
+                          newInForInit: inForInit,
+                          newAtStatementBegin: atStatementBegin);
+    out("(");
+    visitCommaSeparated(call.arguments, ASSIGNMENT,
+                        newInForInit: false, newAtStatementBegin: false);
+    out(")");
+  }
+
+  visitBinary(Binary binary) {
+    Expression left = binary.left;
+    Expression right = binary.right;
+    String op = binary.op;
+    int leftPrecedenceRequirement;
+    int rightPrecedenceRequirement;
+    switch (op) {
+      case "||":
+        leftPrecedenceRequirement = LOGICAL_OR;
+        // x || (y || z) <=> (x || y) || z.
+        rightPrecedenceRequirement = LOGICAL_OR;
+        break;
+      case "&&":
+        leftPrecedenceRequirement = LOGICAL_AND;
+        // x && (y && z) <=> (x && y) && z.
+        rightPrecedenceRequirement = LOGICAL_AND;
+        break;
+      case "|":
+        leftPrecedenceRequirement = BIT_OR;
+        // x | (y | z) <=> (x | y) | z.
+        rightPrecedenceRequirement = BIT_OR;
+        break;
+      case "^":
+        leftPrecedenceRequirement = BIT_XOR;
+        // x ^ (y ^ z) <=> (x ^ y) ^ z.
+        rightPrecedenceRequirement = BIT_XOR;
+        break;
+      case "&":
+        leftPrecedenceRequirement = BIT_AND;
+        // x & (y & z) <=> (x & y) & z.
+        rightPrecedenceRequirement = BIT_AND;
+        break;
+      case "==":
+      case "!=":
+      case "===":
+      case "!==":
+        leftPrecedenceRequirement = EQUALITY;
+        rightPrecedenceRequirement = RELATIONAL;
+        break;
+      case "<":
+      case ">":
+      case "<=":
+      case ">=":
+      case "instanceof":
+      case "in":
+        leftPrecedenceRequirement = RELATIONAL;
+        rightPrecedenceRequirement = SHIFT;
+        break;
+      case ">>":
+      case "<<":
+      case ">>>":
+        leftPrecedenceRequirement = SHIFT;
+        rightPrecedenceRequirement = ADDITIVE;
+        break;
+      case "+":
+      case "-":
+        leftPrecedenceRequirement = ADDITIVE;
+        // We cannot remove parenthesis for "+" because
+        //   x + (y + z) <!=> (x + y) + z:
+        // Example:
+        //   "a" + (1 + 2) => "a3";
+        //   ("a" + 1) + 2 => "a12";
+        rightPrecedenceRequirement = MULTIPLICATIVE;
+        break;
+      case "*":
+      case "/":
+      case "%":
+        leftPrecedenceRequirement = MULTIPLICATIVE;
+        // We cannot remove parenthesis for "*" because of precision issues.
+        rightPrecedenceRequirement = UNARY;
+        break;
+      default:
+        compiler.internalError("Forgot operator: $op");
+    }
+
+    visitNestedExpression(left, leftPrecedenceRequirement,
+                          newInForInit: inForInit,
+                          newAtStatementBegin: atStatementBegin);
+
+    if (op == "in" || op == "instanceof") {
+      // There are cases where the space is not required but without further
+      // analysis we cannot know.
+      out(" ");
+      out(op);
+      out(" ");
+    } else {
+      spaceOut();
+      out(op);
+      spaceOut();
+    }
+    visitNestedExpression(right, rightPrecedenceRequirement,
+                          newInForInit: inForInit,
+                          newAtStatementBegin: false);
+  }
+
+  visitPrefix(Prefix unary) {
+    String op = unary.op;
+    switch (op) {
+      case "delete":
+      case "void":
+      case "typeof":
+        // There are cases where the space is not required but without further
+        // analysis we cannot know.
+        out(op);
+        out(" ");
+        break;
+      case "+":
+      case "++":
+        if (lastCharCode == charCodes.$PLUS) out(" ");
+        out(op);
+        break;
+      case "-":
+      case "--":
+        if (lastCharCode == charCodes.$MINUS) out(" ");
+        out(op);
+        break;
+      default:
+        out(op);
+    }
+    visitNestedExpression(unary.argument, UNARY,
+                          newInForInit: inForInit, newAtStatementBegin: false);
+  }
+
+  visitPostfix(Postfix postfix) {
+    visitNestedExpression(postfix.argument, LEFT_HAND_SIDE,
+                          newInForInit: inForInit,
+                          newAtStatementBegin: atStatementBegin);
+    out(postfix.op);
+  }
+
+  visitVariableUse(VariableUse ref) {
+    out(ref.name);
+  }
+
+  visitThis(This node) {
+    out("this");
+  }
+
+  visitVariableDeclaration(VariableDeclaration decl) {
+    out(decl.name);
+  }
+
+  visitParameter(Parameter param) {
+    out(param.name);
+  }
+
+  bool isDigit(int charCode) {
+    return charCodes.$0 <= charCode && charCode <= charCodes.$9;
+  }
+
+  bool isValidJavaScriptId(String field) {
+    if (field.length < 3) return false;
+    // Ignore the leading and trailing string-delimiter.
+    for (int i = 1; i < field.length - 1; i++) {
+      // TODO(floitsch): allow more characters.
+      int charCode = field.charCodeAt(i);
+      if (!(charCodes.$a <= charCode && charCode <= charCodes.$z ||
+            charCodes.$A <= charCode && charCode <= charCodes.$Z ||
+            charCode == charCodes.$$ ||
+            charCode == charCodes.$_ ||
+            i != 1 && isDigit(charCode))) {
+        return false;
+      }
+    }
+    // TODO(floitsch): normally we should also check that the field is not
+    // a reserved word.
+    return true;
+  }
+
+  visitAccess(PropertyAccess access) {
+    visitNestedExpression(access.receiver, CALL,
+                          newInForInit: inForInit,
+                          newAtStatementBegin: atStatementBegin);
+    Node selector = access.selector;
+    if (selector is LiteralString) {
+      String fieldWithQuotes = (selector as LiteralString).value;
+      if (isValidJavaScriptId(fieldWithQuotes)) {
+        if (isDigit(lastCharCode)) out(" ");
+        out(".");
+        out(fieldWithQuotes.substring(1, fieldWithQuotes.length - 1));
+        return;
+      }
+    }
+    out("[");
+    visitNestedExpression(selector, EXPRESSION,
+                          newInForInit: false, newAtStatementBegin: false);
+    out("]");
+  }
+
+  visitNamedFunction(NamedFunction namedFunction) {
+    functionOut(namedFunction.function, namedFunction.name);
+  }
+
+  visitFun(Fun fun) {
+    functionOut(fun, null);
+  }
+
+  visitLiteralBool(LiteralBool node) {
+    out(node.value ? "true" : "false");
+  }
+
+  visitLiteralString(LiteralString node) {
+    out(node.value);
+  }
+
+  visitLiteralNumber(LiteralNumber node) {
+    int charCode = node.value.charCodeAt(0);
+    if (charCode == charCodes.$MINUS && lastCharCode == charCodes.$MINUS) {
+      out(" ");
+    }
+    out(node.value);
+  }
+
+  visitLiteralNull(LiteralNull node) {
+    out("null");
+  }
+
+  visitArrayInitializer(ArrayInitializer node) {
+    out("[");
+    List<ArrayElement> elements = node.elements;
+    int elementIndex = 0;
+    for (int i = 0; i < node.length; i++) {
+      if (elementIndex < elements.length &&
+          elements[elementIndex].index == i) {
+        visitNestedExpression(elements[elementIndex].value, ASSIGNMENT,
+                              newInForInit: false, newAtStatementBegin: false);
+        elementIndex++;
+        // We can avoid a trailing "," if there was an element just before. So
+        // `[1]` and `[1,]` are the same, but `[,]` and `[]` are not.
+        if (i != node.length - 1) {
+          out(",");
+          spaceOut();
+        }
+      } else {
+        out(",");
+      }
+    }
+    out("]");
+  }
+
+  visitArrayElement(ArrayElement node) {
+    throw "Unreachable";
+  }
+
+  visitObjectInitializer(ObjectInitializer node) {
+    out("{");
+    List<Property> properties = node.properties;
+    for (int i = 0; i < properties.length; i++) {
+      if (i != 0) {
+        out(",");
+        spaceOut();
+      }
+      visitProperty(properties[i]);
+    }
+    out("}");
+  }
+
+  visitProperty(Property node) {
+    if (node.name is LiteralString) {
+      String name = (node.name as LiteralString).value;
+      if (isValidJavaScriptId(name)) {
+        out(name.substring(1, name.length - 1));
+      } else {
+        out(name);
+      }
+    } else {
+      assert(node.name is LiteralNumber);
+      out((node.name as LiteralNumber).value);
+    }
+    out(":");
+    spaceOut();
+    visitNestedExpression(node.value, ASSIGNMENT,
+                          newInForInit: false, newAtStatementBegin: false);
+  }
+
+  visitRegExpLiteral(RegExpLiteral node) {
+    out(node.pattern);
+  }
+
+  visitLiteralExpression(LiteralExpression node) {
+    String template = node.template;
+    List<Expression> inputs = node.inputs;
+
+    List<String> parts = template.split('#');
+    if (parts.length != inputs.length + 1) {
+      compiler.internalError('Wrong number of arguments for JS: $template');
+    }
+    out("(");
+    out(parts[0]);
+    for (int i = 0; i < inputs.length; i++) {
+      visit(inputs[i]);
+      out(parts[i + 1]);
+    }
+    out(")");
+  }
+
+  visitLiteralStatement(LiteralStatement node) {
+    outLn(node.code);
+  }
+}
+
+leg.CodeBuffer prettyPrint(Node node,
+                           leg.Compiler compiler,
+                           Dynamic positionElement) {
+  Printer printer = new Printer(compiler, positionElement);
+  printer.visit(node);
+  return printer.outBuffer;
+}