angular-docs-cn/packages/compiler/src/render3/view/util.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 {ConstantPool} from '../../constant_pool';
import * as o from '../../output/output_ast';
import {splitAtColon} from '../../util';
import * as t from '../r3_ast';
import {R3QueryMetadata} from './api';
import {isI18nAttribute} from './i18n/util';

/** Name of the temporary to use during data binding */
export const TEMPORARY_NAME = '_t';

/** Name of the context parameter passed into a template function */
export const CONTEXT_NAME = 'ctx';

/** Name of the RenderFlag passed into a template function */
export const RENDER_FLAGS = 'rf';

/** The prefix reference variables */
export const REFERENCE_PREFIX = '_r';

/** The name of the implicit context reference */
export const IMPLICIT_REFERENCE = '$implicit';

/** Non bindable attribute name **/
export const NON_BINDABLE_ATTR = 'ngNonBindable';

/**
 * Creates an allocator for a temporary variable.
 *
 * A variable declaration is added to the statements the first time the allocator is invoked.
 */
export function temporaryAllocator(statements: o.Statement[], name: string): () => o.ReadVarExpr {
  let temp: o.ReadVarExpr|null = null;
  return () => {
    if (!temp) {
      statements.push(new o.DeclareVarStmt(TEMPORARY_NAME, undefined, o.DYNAMIC_TYPE));
      temp = o.variable(name);
    }
    return temp;
  };
}


export function unsupported(feature: string): never {
  if (this) {
    throw new Error(`Builder ${this.constructor.name} doesn't support ${feature} yet`);
  }
  throw new Error(`Feature ${feature} is not supported yet`);
}

export function invalid<T>(arg: o.Expression | o.Statement | t.Node): never {
  throw new Error(
      `Invalid state: Visitor ${this.constructor.name} doesn't handle ${o.constructor.name}`);
}

export function asLiteral(value: any): o.Expression {
  if (Array.isArray(value)) {
    return o.literalArr(value.map(asLiteral));
  }
  return o.literal(value, o.INFERRED_TYPE);
}

export function conditionallyCreateMapObjectLiteral(
    keys: {[key: string]: string | string[]}, keepDeclared?: boolean): o.Expression|null {
  if (Object.getOwnPropertyNames(keys).length > 0) {
    return mapToExpression(keys, keepDeclared);
  }
  return null;
}

function mapToExpression(
    map: {[key: string]: string | string[]}, keepDeclared?: boolean): o.Expression {
  return o.literalMap(Object.getOwnPropertyNames(map).map(key => {
    // canonical syntax: `dirProp: publicProp`
    // if there is no `:`, use dirProp = elProp
    const value = map[key];
    let declaredName: string;
    let publicName: string;
    let minifiedName: string;
    if (Array.isArray(value)) {
      [publicName, declaredName] = value;
    } else {
      [declaredName, publicName] = splitAtColon(key, [key, value]);
    }
    minifiedName = declaredName;
    return {
      key: minifiedName,
      quoted: false,
      value: (keepDeclared && publicName !== declaredName) ?
          o.literalArr([asLiteral(publicName), asLiteral(declaredName)]) :
          asLiteral(publicName)
    };
  }));
}

/**
 *  Remove trailing null nodes as they are implied.
 */
export function trimTrailingNulls(parameters: o.Expression[]): o.Expression[] {
  while (o.isNull(parameters[parameters.length - 1])) {
    parameters.pop();
  }
  return parameters;
}

export function getQueryPredicate(
    query: R3QueryMetadata, constantPool: ConstantPool): o.Expression {
  if (Array.isArray(query.predicate)) {
    let predicate: o.Expression[] = [];
    query.predicate.forEach((selector: string): void => {
      // Each item in predicates array may contain strings with comma-separated refs
      // (for ex. 'ref, ref1, ..., refN'), thus we extract individual refs and store them
      // as separate array entities
      const selectors = selector.split(',').map(token => o.literal(token.trim()));
      predicate.push(...selectors);
    });
    return constantPool.getConstLiteral(o.literalArr(predicate), true);
  } else {
    return query.predicate;
  }
}

export function noop() {}

export class DefinitionMap {
  values: {key: string, quoted: boolean, value: o.Expression}[] = [];

  set(key: string, value: o.Expression|null): void {
    if (value) {
      this.values.push({key, value, quoted: false});
    }
  }

  toLiteralMap(): o.LiteralMapExpr { return o.literalMap(this.values); }
}

/**
 * Extract a map of properties to values for a given element or template node, which can be used
 * by the directive matching machinery.
 *
 * @param elOrTpl the element or template in question
 * @return an object set up for directive matching. For attributes on the element/template, this
 * object maps a property name to its (static) value. For any bindings, this map simply maps the
 * property name to an empty string.
 */
export function getAttrsForDirectiveMatching(elOrTpl: t.Element | t.Template):
    {[name: string]: string} {
  const attributesMap: {[name: string]: string} = {};

  elOrTpl.attributes.forEach(a => {
    if (!isI18nAttribute(a.name)) {
      attributesMap[a.name] = a.value;
    }
  });
  elOrTpl.inputs.forEach(i => { attributesMap[i.name] = ''; });
  elOrTpl.outputs.forEach(o => { attributesMap[o.name] = ''; });

  return attributesMap;
}