angular/packages/compiler/src/output/abstract_emitter.ts

/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {ParseSourceSpan} from '../parse_util';

import * as o from './output_ast';
import {SourceMapGenerator} from './source_map';

const _SINGLE_QUOTE_ESCAPE_STRING_RE = /'|\\|\n|\r|\$/g;
const _LEGAL_IDENTIFIER_RE = /^[$A-Z_][0-9A-Z_$]*$/i;
const _INDENT_WITH = '  ';
export const CATCH_ERROR_VAR = o.variable('error', null, null);
export const CATCH_STACK_VAR = o.variable('stack', null, null);

export interface OutputEmitter {
  emitStatements(genFilePath: string, stmts: o.Statement[], preamble?: string|null): string;
}

class _EmittedLine {
  partsLength = 0;
  parts: string[] = [];
  srcSpans: (ParseSourceSpan|null)[] = [];
  constructor(public indent: number) {}
}

export class EmitterVisitorContext {
  static createRoot(): EmitterVisitorContext { return new EmitterVisitorContext(0); }

  private _lines: _EmittedLine[];
  private _classes: o.ClassStmt[] = [];
  private _preambleLineCount = 0;

  constructor(private _indent: number) { this._lines = [new _EmittedLine(_indent)]; }

  private get _currentLine(): _EmittedLine { return this._lines[this._lines.length - 1]; }

  println(from?: {sourceSpan: ParseSourceSpan | null}|null, lastPart: string = ''): void {
    this.print(from || null, lastPart, true);
  }

  lineIsEmpty(): boolean { return this._currentLine.parts.length === 0; }

  lineLength(): number {
    return this._currentLine.indent * _INDENT_WITH.length + this._currentLine.partsLength;
  }

  print(from: {sourceSpan: ParseSourceSpan | null}|null, part: string, newLine: boolean = false) {
    if (part.length > 0) {
      this._currentLine.parts.push(part);
      this._currentLine.partsLength += part.length;
      this._currentLine.srcSpans.push(from && from.sourceSpan || null);
    }
    if (newLine) {
      this._lines.push(new _EmittedLine(this._indent));
    }
  }

  removeEmptyLastLine() {
    if (this.lineIsEmpty()) {
      this._lines.pop();
    }
  }

  incIndent() {
    this._indent++;
    if (this.lineIsEmpty()) {
      this._currentLine.indent = this._indent;
    }
  }

  decIndent() {
    this._indent--;
    if (this.lineIsEmpty()) {
      this._currentLine.indent = this._indent;
    }
  }

  pushClass(clazz: o.ClassStmt) { this._classes.push(clazz); }

  popClass(): o.ClassStmt { return this._classes.pop() !; }

  get currentClass(): o.ClassStmt|null {
    return this._classes.length > 0 ? this._classes[this._classes.length - 1] : null;
  }

  toSource(): string {
    return this.sourceLines
        .map(l => l.parts.length > 0 ? _createIndent(l.indent) + l.parts.join('') : '')
        .join('\n');
  }

  toSourceMapGenerator(genFilePath: string, startsAtLine: number = 0): SourceMapGenerator {
    const map = new SourceMapGenerator(genFilePath);

    let firstOffsetMapped = false;
    const mapFirstOffsetIfNeeded = () => {
      if (!firstOffsetMapped) {
        // Add a single space so that tools won't try to load the file from disk.
        // Note: We are using virtual urls like `ng:///`, so we have to
        // provide a content here.
        map.addSource(genFilePath, ' ').addMapping(0, genFilePath, 0, 0);
        firstOffsetMapped = true;
      }
    };

    for (let i = 0; i < startsAtLine; i++) {
      map.addLine();
      mapFirstOffsetIfNeeded();
    }

    this.sourceLines.forEach((line, lineIdx) => {
      map.addLine();

      const spans = line.srcSpans;
      const parts = line.parts;
      let col0 = line.indent * _INDENT_WITH.length;
      let spanIdx = 0;
      // skip leading parts without source spans
      while (spanIdx < spans.length && !spans[spanIdx]) {
        col0 += parts[spanIdx].length;
        spanIdx++;
      }
      if (spanIdx < spans.length && lineIdx === 0 && col0 === 0) {
        firstOffsetMapped = true;
      } else {
        mapFirstOffsetIfNeeded();
      }

      while (spanIdx < spans.length) {
        const span = spans[spanIdx] !;
        const source = span.start.file;
        const sourceLine = span.start.line;
        const sourceCol = span.start.col;
        map.addSource(source.url, source.content)
            .addMapping(col0, source.url, sourceLine, sourceCol);

        col0 += parts[spanIdx].length;
        spanIdx++;

        // assign parts without span or the same span to the previous segment
        while (spanIdx < spans.length && (span === spans[spanIdx] || !spans[spanIdx])) {
          col0 += parts[spanIdx].length;
          spanIdx++;
        }
      }
    });

    return map;
  }

  setPreambleLineCount(count: number) { return this._preambleLineCount = count; }

  spanOf(line: number, column: number): ParseSourceSpan|null {
    const emittedLine = this._lines[line - this._preambleLineCount];
    if (emittedLine) {
      let columnsLeft = column - _createIndent(emittedLine.indent).length;
      for (let partIndex = 0; partIndex < emittedLine.parts.length; partIndex++) {
        const part = emittedLine.parts[partIndex];
        if (part.length > columnsLeft) {
          return emittedLine.srcSpans[partIndex];
        }
        columnsLeft -= part.length;
      }
    }
    return null;
  }

  private get sourceLines(): _EmittedLine[] {
    if (this._lines.length && this._lines[this._lines.length - 1].parts.length === 0) {
      return this._lines.slice(0, -1);
    }
    return this._lines;
  }
}

export abstract class AbstractEmitterVisitor implements o.StatementVisitor, o.ExpressionVisitor {
  constructor(private _escapeDollarInStrings: boolean) {}

  visitExpressionStmt(stmt: o.ExpressionStatement, ctx: EmitterVisitorContext): any {
    stmt.expr.visitExpression(this, ctx);
    ctx.println(stmt, ';');
    return null;
  }

  visitReturnStmt(stmt: o.ReturnStatement, ctx: EmitterVisitorContext): any {
    ctx.print(stmt, `return `);
    stmt.value.visitExpression(this, ctx);
    ctx.println(stmt, ';');
    return null;
  }

  abstract visitCastExpr(ast: o.CastExpr, context: any): any;

  abstract visitDeclareClassStmt(stmt: o.ClassStmt, ctx: EmitterVisitorContext): any;

  visitIfStmt(stmt: o.IfStmt, ctx: EmitterVisitorContext): any {
    ctx.print(stmt, `if (`);
    stmt.condition.visitExpression(this, ctx);
    ctx.print(stmt, `) {`);
    const hasElseCase = stmt.falseCase != null && stmt.falseCase.length > 0;
    if (stmt.trueCase.length <= 1 && !hasElseCase) {
      ctx.print(stmt, ` `);
      this.visitAllStatements(stmt.trueCase, ctx);
      ctx.removeEmptyLastLine();
      ctx.print(stmt, ` `);
    } else {
      ctx.println();
      ctx.incIndent();
      this.visitAllStatements(stmt.trueCase, ctx);
      ctx.decIndent();
      if (hasElseCase) {
        ctx.println(stmt, `} else {`);
        ctx.incIndent();
        this.visitAllStatements(stmt.falseCase, ctx);
        ctx.decIndent();
      }
    }
    ctx.println(stmt, `}`);
    return null;
  }

  abstract visitTryCatchStmt(stmt: o.TryCatchStmt, ctx: EmitterVisitorContext): any;

  visitThrowStmt(stmt: o.ThrowStmt, ctx: EmitterVisitorContext): any {
    ctx.print(stmt, `throw `);
    stmt.error.visitExpression(this, ctx);
    ctx.println(stmt, `;`);
    return null;
  }
  visitCommentStmt(stmt: o.CommentStmt, ctx: EmitterVisitorContext): any {
    if (stmt.multiline) {
      ctx.println(stmt, `/* ${stmt.comment} */`);
    } else {
      stmt.comment.split('\n').forEach((line) => { ctx.println(stmt, `// ${line}`); });
    }
    return null;
  }
  visitJSDocCommentStmt(stmt: o.JSDocCommentStmt, ctx: EmitterVisitorContext) {
    ctx.println(stmt, `/*${stmt.toString()}*/`);
    return null;
  }

  abstract visitDeclareVarStmt(stmt: o.DeclareVarStmt, ctx: EmitterVisitorContext): any;

  visitWriteVarExpr(expr: o.WriteVarExpr, ctx: EmitterVisitorContext): any {
    const lineWasEmpty = ctx.lineIsEmpty();
    if (!lineWasEmpty) {
      ctx.print(expr, '(');
    }
    ctx.print(expr, `${expr.name} = `);
    expr.value.visitExpression(this, ctx);
    if (!lineWasEmpty) {
      ctx.print(expr, ')');
    }
    return null;
  }
  visitWriteKeyExpr(expr: o.WriteKeyExpr, ctx: EmitterVisitorContext): any {
    const lineWasEmpty = ctx.lineIsEmpty();
    if (!lineWasEmpty) {
      ctx.print(expr, '(');
    }
    expr.receiver.visitExpression(this, ctx);
    ctx.print(expr, `[`);
    expr.index.visitExpression(this, ctx);
    ctx.print(expr, `] = `);
    expr.value.visitExpression(this, ctx);
    if (!lineWasEmpty) {
      ctx.print(expr, ')');
    }
    return null;
  }
  visitWritePropExpr(expr: o.WritePropExpr, ctx: EmitterVisitorContext): any {
    const lineWasEmpty = ctx.lineIsEmpty();
    if (!lineWasEmpty) {
      ctx.print(expr, '(');
    }
    expr.receiver.visitExpression(this, ctx);
    ctx.print(expr, `.${expr.name} = `);
    expr.value.visitExpression(this, ctx);
    if (!lineWasEmpty) {
      ctx.print(expr, ')');
    }
    return null;
  }
  visitInvokeMethodExpr(expr: o.InvokeMethodExpr, ctx: EmitterVisitorContext): any {
    expr.receiver.visitExpression(this, ctx);
    let name = expr.name;
    if (expr.builtin != null) {
      name = this.getBuiltinMethodName(expr.builtin);
      if (name == null) {
        // some builtins just mean to skip the call.
        return null;
      }
    }
    ctx.print(expr, `.${name}(`);
    this.visitAllExpressions(expr.args, ctx, `,`);
    ctx.print(expr, `)`);
    return null;
  }

  abstract getBuiltinMethodName(method: o.BuiltinMethod): string;

  visitInvokeFunctionExpr(expr: o.InvokeFunctionExpr, ctx: EmitterVisitorContext): any {
    expr.fn.visitExpression(this, ctx);
    ctx.print(expr, `(`);
    this.visitAllExpressions(expr.args, ctx, ',');
    ctx.print(expr, `)`);
    return null;
  }
  visitWrappedNodeExpr(ast: o.WrappedNodeExpr<any>, ctx: EmitterVisitorContext): any {
    throw new Error('Abstract emitter cannot visit WrappedNodeExpr.');
  }
  visitTypeofExpr(expr: o.TypeofExpr, ctx: EmitterVisitorContext): any {
    ctx.print(expr, 'typeof ');
    expr.expr.visitExpression(this, ctx);
  }
  visitReadVarExpr(ast: o.ReadVarExpr, ctx: EmitterVisitorContext): any {
    let varName = ast.name !;
    if (ast.builtin != null) {
      switch (ast.builtin) {
        case o.BuiltinVar.Super:
          varName = 'super';
          break;
        case o.BuiltinVar.This:
          varName = 'this';
          break;
        case o.BuiltinVar.CatchError:
          varName = CATCH_ERROR_VAR.name !;
          break;
        case o.BuiltinVar.CatchStack:
          varName = CATCH_STACK_VAR.name !;
          break;
        default:
          throw new Error(`Unknown builtin variable ${ast.builtin}`);
      }
    }
    ctx.print(ast, varName);
    return null;
  }
  visitInstantiateExpr(ast: o.InstantiateExpr, ctx: EmitterVisitorContext): any {
    ctx.print(ast, `new `);
    ast.classExpr.visitExpression(this, ctx);
    ctx.print(ast, `(`);
    this.visitAllExpressions(ast.args, ctx, ',');
    ctx.print(ast, `)`);
    return null;
  }

  visitLiteralExpr(ast: o.LiteralExpr, ctx: EmitterVisitorContext): any {
    const value = ast.value;
    if (typeof value === 'string') {
      ctx.print(ast, escapeIdentifier(value, this._escapeDollarInStrings));
    } else {
      ctx.print(ast, `${value}`);
    }
    return null;
  }

  abstract visitExternalExpr(ast: o.ExternalExpr, ctx: EmitterVisitorContext): any;

  visitConditionalExpr(ast: o.ConditionalExpr, ctx: EmitterVisitorContext): any {
    ctx.print(ast, `(`);
    ast.condition.visitExpression(this, ctx);
    ctx.print(ast, '? ');
    ast.trueCase.visitExpression(this, ctx);
    ctx.print(ast, ': ');
    ast.falseCase !.visitExpression(this, ctx);
    ctx.print(ast, `)`);
    return null;
  }
  visitNotExpr(ast: o.NotExpr, ctx: EmitterVisitorContext): any {
    ctx.print(ast, '!');
    ast.condition.visitExpression(this, ctx);
    return null;
  }
  visitAssertNotNullExpr(ast: o.AssertNotNull, ctx: EmitterVisitorContext): any {
    ast.condition.visitExpression(this, ctx);
    return null;
  }
  abstract visitFunctionExpr(ast: o.FunctionExpr, ctx: EmitterVisitorContext): any;
  abstract visitDeclareFunctionStmt(stmt: o.DeclareFunctionStmt, context: any): any;

  visitBinaryOperatorExpr(ast: o.BinaryOperatorExpr, ctx: EmitterVisitorContext): any {
    let opStr: string;
    switch (ast.operator) {
      case o.BinaryOperator.Equals:
        opStr = '==';
        break;
      case o.BinaryOperator.Identical:
        opStr = '===';
        break;
      case o.BinaryOperator.NotEquals:
        opStr = '!=';
        break;
      case o.BinaryOperator.NotIdentical:
        opStr = '!==';
        break;
      case o.BinaryOperator.And:
        opStr = '&&';
        break;
      case o.BinaryOperator.BitwiseAnd:
        opStr = '&';
        break;
      case o.BinaryOperator.Or:
        opStr = '||';
        break;
      case o.BinaryOperator.Plus:
        opStr = '+';
        break;
      case o.BinaryOperator.Minus:
        opStr = '-';
        break;
      case o.BinaryOperator.Divide:
        opStr = '/';
        break;
      case o.BinaryOperator.Multiply:
        opStr = '*';
        break;
      case o.BinaryOperator.Modulo:
        opStr = '%';
        break;
      case o.BinaryOperator.Lower:
        opStr = '<';
        break;
      case o.BinaryOperator.LowerEquals:
        opStr = '<=';
        break;
      case o.BinaryOperator.Bigger:
        opStr = '>';
        break;
      case o.BinaryOperator.BiggerEquals:
        opStr = '>=';
        break;
      default:
        throw new Error(`Unknown operator ${ast.operator}`);
    }
    if (ast.parens) ctx.print(ast, `(`);
    ast.lhs.visitExpression(this, ctx);
    ctx.print(ast, ` ${opStr} `);
    ast.rhs.visitExpression(this, ctx);
    if (ast.parens) ctx.print(ast, `)`);
    return null;
  }

  visitReadPropExpr(ast: o.ReadPropExpr, ctx: EmitterVisitorContext): any {
    ast.receiver.visitExpression(this, ctx);
    ctx.print(ast, `.`);
    ctx.print(ast, ast.name);
    return null;
  }
  visitReadKeyExpr(ast: o.ReadKeyExpr, ctx: EmitterVisitorContext): any {
    ast.receiver.visitExpression(this, ctx);
    ctx.print(ast, `[`);
    ast.index.visitExpression(this, ctx);
    ctx.print(ast, `]`);
    return null;
  }
  visitLiteralArrayExpr(ast: o.LiteralArrayExpr, ctx: EmitterVisitorContext): any {
    ctx.print(ast, `[`);
    this.visitAllExpressions(ast.entries, ctx, ',');
    ctx.print(ast, `]`);
    return null;
  }
  visitLiteralMapExpr(ast: o.LiteralMapExpr, ctx: EmitterVisitorContext): any {
    ctx.print(ast, `{`);
    this.visitAllObjects(entry => {
      ctx.print(ast, `${escapeIdentifier(entry.key, this._escapeDollarInStrings, entry.quoted)}:`);
      entry.value.visitExpression(this, ctx);
    }, ast.entries, ctx, ',');
    ctx.print(ast, `}`);
    return null;
  }
  visitCommaExpr(ast: o.CommaExpr, ctx: EmitterVisitorContext): any {
    ctx.print(ast, '(');
    this.visitAllExpressions(ast.parts, ctx, ',');
    ctx.print(ast, ')');
    return null;
  }
  visitAllExpressions(expressions: o.Expression[], ctx: EmitterVisitorContext, separator: string):
      void {
    this.visitAllObjects(expr => expr.visitExpression(this, ctx), expressions, ctx, separator);
  }

  visitAllObjects<T>(
      handler: (t: T) => void, expressions: T[], ctx: EmitterVisitorContext,
      separator: string): void {
    let incrementedIndent = false;
    for (let i = 0; i < expressions.length; i++) {
      if (i > 0) {
        if (ctx.lineLength() > 80) {
          ctx.print(null, separator, true);
          if (!incrementedIndent) {
            // continuation are marked with double indent.
            ctx.incIndent();
            ctx.incIndent();
            incrementedIndent = true;
          }
        } else {
          ctx.print(null, separator, false);
        }
      }
      handler(expressions[i]);
    }
    if (incrementedIndent) {
      // continuation are marked with double indent.
      ctx.decIndent();
      ctx.decIndent();
    }
  }

  visitAllStatements(statements: o.Statement[], ctx: EmitterVisitorContext): void {
    statements.forEach((stmt) => stmt.visitStatement(this, ctx));
  }
}

export function escapeIdentifier(
    input: string, escapeDollar: boolean, alwaysQuote: boolean = true): any {
  if (input == null) {
    return null;
  }
  const body = input.replace(_SINGLE_QUOTE_ESCAPE_STRING_RE, (...match: string[]) => {
    if (match[0] == '$') {
      return escapeDollar ? '\\$' : '$';
    } else if (match[0] == '\n') {
      return '\\n';
    } else if (match[0] == '\r') {
      return '\\r';
    } else {
      return `\\${match[0]}`;
    }
  });
  const requiresQuotes = alwaysQuote || !_LEGAL_IDENTIFIER_RE.test(body);
  return requiresQuotes ? `'${body}'` : body;
}

function _createIndent(count: number): string {
  let res = '';
  for (let i = 0; i < count; i++) {
    res += _INDENT_WITH;
  }
  return res;
}