angular-docs-cn/packages/compiler/test/expression_parser/parser_spec.ts

/**
 * @license
 * Copyright Google LLC 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 {ASTWithSource, BindingPipe, Interpolation, ParserError, TemplateBinding, VariableBinding} from '@angular/compiler/src/expression_parser/ast';
import {Lexer} from '@angular/compiler/src/expression_parser/lexer';
import {Parser, SplitInterpolation} from '@angular/compiler/src/expression_parser/parser';
import {expect} from '@angular/platform-browser/testing/src/matchers';


import {unparse, unparseWithSpan} from './utils/unparser';
import {validate} from './utils/validator';

describe('parser', () => {
  describe('parseAction', () => {
    it('should parse numbers', () => {
      checkAction('1');
    });

    it('should parse strings', () => {
      checkAction('\'1\'', '"1"');
      checkAction('"1"');
    });

    it('should parse null', () => {
      checkAction('null');
    });

    it('should parse undefined', () => {
      checkAction('undefined');
    });

    it('should parse unary - expressions', () => {
      checkAction('-1', '0 - 1');
      checkAction('+1', '1 - 0');
      checkAction(`-'1'`, `0 - "1"`);
      checkAction(`+'1'`, `"1" - 0`);
    });

    it('should parse unary ! expressions', () => {
      checkAction('!true');
      checkAction('!!true');
      checkAction('!!!true');
    });

    it('should parse postfix ! expression', () => {
      checkAction('true!');
      checkAction('a!.b');
      checkAction('a!!!!.b');
    });

    it('should parse multiplicative expressions', () => {
      checkAction('3*4/2%5', '3 * 4 / 2 % 5');
    });

    it('should parse additive expressions', () => {
      checkAction('3 + 6 - 2');
    });

    it('should parse relational expressions', () => {
      checkAction('2 < 3');
      checkAction('2 > 3');
      checkAction('2 <= 2');
      checkAction('2 >= 2');
    });

    it('should parse equality expressions', () => {
      checkAction('2 == 3');
      checkAction('2 != 3');
    });

    it('should parse strict equality expressions', () => {
      checkAction('2 === 3');
      checkAction('2 !== 3');
    });

    it('should parse expressions', () => {
      checkAction('true && true');
      checkAction('true || false');
    });

    it('should parse grouped expressions', () => {
      checkAction('(1 + 2) * 3', '1 + 2 * 3');
    });

    it('should ignore comments in expressions', () => {
      checkAction('a //comment', 'a');
    });

    it('should retain // in string literals', () => {
      checkAction(`"http://www.google.com"`, `"http://www.google.com"`);
    });

    it('should parse an empty string', () => {
      checkAction('');
    });

    describe('literals', () => {
      it('should parse array', () => {
        checkAction('[1][0]');
        checkAction('[[1]][0][0]');
        checkAction('[]');
        checkAction('[].length');
        checkAction('[1, 2].length');
      });

      it('should parse map', () => {
        checkAction('{}');
        checkAction('{a: 1, "b": 2}[2]');
        checkAction('{}["a"]');
      });

      it('should only allow identifier, string, or keyword as map key', () => {
        expectActionError('{(:0}', 'expected identifier, keyword, or string');
        expectActionError('{1234:0}', 'expected identifier, keyword, or string');
      });
    });

    describe('member access', () => {
      it('should parse field access', () => {
        checkAction('a');
        checkAction('this.a', 'a');
        checkAction('a.a');
      });

      it('should only allow identifier or keyword as member names', () => {
        expectActionError('x.(', 'identifier or keyword');
        expectActionError('x. 1234', 'identifier or keyword');
        expectActionError('x."foo"', 'identifier or keyword');
      });

      it('should parse safe field access', () => {
        checkAction('a?.a');
        checkAction('a.a?.a');
      });
    });

    describe('method calls', () => {
      it('should parse method calls', () => {
        checkAction('fn()');
        checkAction('add(1, 2)');
        checkAction('a.add(1, 2)');
        checkAction('fn().add(1, 2)');
      });
    });

    describe('functional calls', () => {
      it('should parse function calls', () => {
        checkAction('fn()(1, 2)');
      });
    });

    describe('conditional', () => {
      it('should parse ternary/conditional expressions', () => {
        checkAction('7 == 3 + 4 ? 10 : 20');
        checkAction('false ? 10 : 20');
      });

      it('should report incorrect ternary operator syntax', () => {
        expectActionError('true?1', 'Conditional expression true?1 requires all 3 expressions');
      });
    });

    describe('assignment', () => {
      it('should support field assignments', () => {
        checkAction('a = 12');
        checkAction('a.a.a = 123');
        checkAction('a = 123; b = 234;');
      });

      it('should report on safe field assignments', () => {
        expectActionError('a?.a = 123', 'cannot be used in the assignment');
      });

      it('should support array updates', () => {
        checkAction('a[0] = 200');
      });
    });

    it('should error when using pipes', () => {
      expectActionError('x|blah', 'Cannot have a pipe');
    });

    it('should store the source in the result', () => {
      expect(parseAction('someExpr', 'someExpr'));
    });

    it('should store the passed-in location', () => {
      expect(parseAction('someExpr', 'location').location).toBe('location');
    });

    it('should report when encountering interpolation', () => {
      expectActionError('{{a()}}', 'Got interpolation ({{}}) where expression was expected');
    });
  });

  describe('parse spans', () => {
    it('should record property read span', () => {
      const ast = parseAction('foo');
      expect(unparseWithSpan(ast)).toContain(['foo', 'foo']);
      expect(unparseWithSpan(ast)).toContain(['foo', '[nameSpan] foo']);
    });

    it('should record accessed property read span', () => {
      const ast = parseAction('foo.bar');
      expect(unparseWithSpan(ast)).toContain(['foo.bar', 'foo.bar']);
      expect(unparseWithSpan(ast)).toContain(['foo.bar', '[nameSpan] bar']);
    });

    it('should record safe property read span', () => {
      const ast = parseAction('foo?.bar');
      expect(unparseWithSpan(ast)).toContain(['foo?.bar', 'foo?.bar']);
      expect(unparseWithSpan(ast)).toContain(['foo?.bar', '[nameSpan] bar']);
    });

    it('should record method call span', () => {
      const ast = parseAction('foo()');
      expect(unparseWithSpan(ast)).toContain(['foo()', 'foo()']);
      expect(unparseWithSpan(ast)).toContain(['foo()', '[nameSpan] foo']);
    });

    it('should record accessed method call span', () => {
      const ast = parseAction('foo.bar()');
      expect(unparseWithSpan(ast)).toContain(['foo.bar()', 'foo.bar()']);
      expect(unparseWithSpan(ast)).toContain(['foo.bar()', '[nameSpan] bar']);
    });

    it('should record safe method call span', () => {
      const ast = parseAction('foo?.bar()');
      expect(unparseWithSpan(ast)).toContain(['foo?.bar()', 'foo?.bar()']);
      expect(unparseWithSpan(ast)).toContain(['foo?.bar()', '[nameSpan] bar']);
    });

    it('should record property write span', () => {
      const ast = parseAction('a = b');
      expect(unparseWithSpan(ast)).toContain(['a = b', 'a = b']);
      expect(unparseWithSpan(ast)).toContain(['a = b', '[nameSpan] a']);
    });

    it('should record accessed property write span', () => {
      const ast = parseAction('a.b = c');
      expect(unparseWithSpan(ast)).toContain(['a.b = c', 'a.b = c']);
      expect(unparseWithSpan(ast)).toContain(['a.b = c', '[nameSpan] b']);
    });
  });

  describe('general error handling', () => {
    it('should report an unexpected token', () => {
      expectActionError('[1,2] trac', 'Unexpected token \'trac\'');
    });

    it('should report reasonable error for unconsumed tokens', () => {
      expectActionError(')', 'Unexpected token ) at column 1 in [)]');
    });

    it('should report a missing expected token', () => {
      expectActionError('a(b', 'Missing expected ) at the end of the expression [a(b]');
    });
  });

  describe('parseBinding', () => {
    describe('pipes', () => {
      it('should parse pipes', () => {
        checkBinding('a(b | c)', 'a((b | c))');
        checkBinding('a.b(c.d(e) | f)', 'a.b((c.d(e) | f))');
        checkBinding('[1, 2, 3] | a', '([1, 2, 3] | a)');
        checkBinding('{a: 1, "b": 2} | c', '({a: 1, "b": 2} | c)');
        checkBinding('a[b] | c', '(a[b] | c)');
        checkBinding('a?.b | c', '(a?.b | c)');
        checkBinding('true | a', '(true | a)');
        checkBinding('a | b:c | d', '((a | b:c) | d)');
        checkBinding('a | b:(c | d)', '(a | b:(c | d))');
      });

      it('should only allow identifier or keyword as formatter names', () => {
        expectBindingError('"Foo"|(', 'identifier or keyword');
        expectBindingError('"Foo"|1234', 'identifier or keyword');
        expectBindingError('"Foo"|"uppercase"', 'identifier or keyword');
      });

      it('should parse quoted expressions', () => {
        checkBinding('a:b', 'a:b');
      });

      it('should not crash when prefix part is not tokenizable', () => {
        checkBinding('"a:b"', '"a:b"');
      });

      it('should ignore whitespace around quote prefix', () => {
        checkBinding(' a :b', 'a:b');
      });

      it('should refuse prefixes that are not single identifiers', () => {
        expectBindingError('a + b:c', '');
        expectBindingError('1:c', '');
      });
    });

    it('should store the source in the result', () => {
      expect(parseBinding('someExpr').source).toBe('someExpr');
    });

    it('should store the passed-in location', () => {
      expect(parseBinding('someExpr', 'location').location).toBe('location');
    });

    it('should report chain expressions', () => {
      expectError(parseBinding('1;2'), 'contain chained expression');
    });

    it('should report assignment', () => {
      expectError(parseBinding('a=2'), 'contain assignments');
    });

    it('should report when encountering interpolation', () => {
      expectBindingError('{{a.b}}', 'Got interpolation ({{}}) where expression was expected');
    });

    it('should parse conditional expression', () => {
      checkBinding('a < b ? a : b');
    });

    it('should ignore comments in bindings', () => {
      checkBinding('a //comment', 'a');
    });

    it('should retain // in string literals', () => {
      checkBinding(`"http://www.google.com"`, `"http://www.google.com"`);
    });

    it('should retain // in : microsyntax', () => {
      checkBinding('one:a//b', 'one:a//b');
    });
  });

  describe('parseTemplateBindings', () => {
    function humanize(bindings: TemplateBinding[]): Array<[string, string | null, boolean]> {
      return bindings.map(binding => {
        const key = binding.key.source;
        const value = binding.value ? binding.value.source : null;
        const keyIsVar = binding instanceof VariableBinding;
        return [key, value, keyIsVar];
      });
    }

    function humanizeSpans(
        bindings: TemplateBinding[], attr: string): Array<[string, string, string | null]> {
      return bindings.map(binding => {
        const {sourceSpan, key, value} = binding;
        const sourceStr = attr.substring(sourceSpan.start, sourceSpan.end);
        const keyStr = attr.substring(key.span.start, key.span.end);
        let valueStr = null;
        if (value) {
          const {start, end} = value instanceof ASTWithSource ? value.ast.sourceSpan : value.span;
          valueStr = attr.substring(start, end);
        }
        return [sourceStr, keyStr, valueStr];
      });
    }

    it('should parse key and value', () => {
      const cases: Array<[string, string, string | null, boolean, string, string, string | null]> =
          [
            // expression, key, value, VariableBinding, source span, key span, value span
            ['*a=""', 'a', null, false, 'a="', 'a', null],
            ['*a="b"', 'a', 'b', false, 'a="b', 'a', 'b'],
            ['*a-b="c"', 'a-b', 'c', false, 'a-b="c', 'a-b', 'c'],
            ['*a="1+1"', 'a', '1+1', false, 'a="1+1', 'a', '1+1'],
          ];
      for (const [attr, key, value, keyIsVar, sourceSpan, keySpan, valueSpan] of cases) {
        const bindings = parseTemplateBindings(attr);
        expect(humanize(bindings)).toEqual([
          [key, value, keyIsVar],
        ]);
        expect(humanizeSpans(bindings, attr)).toEqual([
          [sourceSpan, keySpan, valueSpan],
        ]);
      }
    });

    it('should variable declared via let', () => {
      const bindings = parseTemplateBindings('*a="let b"');
      expect(humanize(bindings)).toEqual([
        // key, value, VariableBinding
        ['a', null, false],
        ['b', null, true],
      ]);
    });

    it('should allow multiple pairs', () => {
      const bindings = parseTemplateBindings('*a="1 b 2"');
      expect(humanize(bindings)).toEqual([
        // key, value, VariableBinding
        ['a', '1', false],
        ['aB', '2', false],
      ]);
    });

    it('should allow space and colon as separators', () => {
      const bindings = parseTemplateBindings('*a="1,b 2"');
      expect(humanize(bindings)).toEqual([
        // key, value, VariableBinding
        ['a', '1', false],
        ['aB', '2', false],
      ]);
    });

    it('should store the templateUrl', () => {
      const bindings = parseTemplateBindings('*a="1,b 2"', '/foo/bar.html');
      expect(humanize(bindings)).toEqual([
        // key, value, VariableBinding
        ['a', '1', false],
        ['aB', '2', false],
      ]);
      expect((bindings[0].value as ASTWithSource).location).toEqual('/foo/bar.html');
    });

    it('should support common usage of ngIf', () => {
      const bindings = parseTemplateBindings('*ngIf="cond | pipe as foo, let x; ngIf as y"');
      expect(humanize(bindings)).toEqual([
        // [ key, value, VariableBinding ]
        ['ngIf', 'cond | pipe', false],
        ['foo', 'ngIf', true],
        ['x', null, true],
        ['y', 'ngIf', true],
      ]);
    });

    it('should support common usage of ngFor', () => {
      let bindings: TemplateBinding[];
      bindings = parseTemplateBindings('*ngFor="let person of people"');
      expect(humanize(bindings)).toEqual([
        // [ key, value, VariableBinding ]
        ['ngFor', null, false],
        ['person', null, true],
        ['ngForOf', 'people', false],
      ]);


      bindings = parseTemplateBindings(
          '*ngFor="let item; of items | slice:0:1 as collection, trackBy: func; index as i"');
      expect(humanize(bindings)).toEqual([
        // [ key, value, VariableBinding ]
        ['ngFor', null, false],
        ['item', null, true],
        ['ngForOf', 'items | slice:0:1', false],
        ['collection', 'ngForOf', true],
        ['ngForTrackBy', 'func', false],
        ['i', 'index', true],
      ]);

      bindings = parseTemplateBindings(
          '*ngFor="let item, of: [1,2,3] | pipe as items; let i=index, count as len"');
      expect(humanize(bindings)).toEqual([
        // [ key, value, VariableBinding ]
        ['ngFor', null, false],
        ['item', null, true],
        ['ngForOf', '[1,2,3] | pipe', false],
        ['items', 'ngForOf', true],
        ['i', 'index', true],
        ['len', 'count', true],
      ]);
    });

    it('should parse pipes', () => {
      const bindings = parseTemplateBindings('*key="value|pipe "');
      expect(humanize(bindings)).toEqual([
        // [ key, value, VariableBinding ]
        ['key', 'value|pipe', false],
      ]);
      const {value} = bindings[0];
      expect(value).toBeAnInstanceOf(ASTWithSource);
      expect((value as ASTWithSource).ast).toBeAnInstanceOf(BindingPipe);
    });

    describe('"let" binding', () => {
      it('should support single declaration', () => {
        const bindings = parseTemplateBindings('*key="let i"');
        expect(humanize(bindings)).toEqual([
          // [ key, value, VariableBinding ]
          ['key', null, false],
          ['i', null, true],
        ]);
      });

      it('should support multiple declarations', () => {
        const bindings = parseTemplateBindings('*key="let a; let b"');
        expect(humanize(bindings)).toEqual([
          // [ key, value, VariableBinding ]
          ['key', null, false],
          ['a', null, true],
          ['b', null, true],
        ]);
      });

      it('should support empty string assignment', () => {
        const bindings = parseTemplateBindings(`*key="let a=''; let b='';"`);
        expect(humanize(bindings)).toEqual([
          // [ key, value, VariableBinding ]
          ['key', null, false],
          ['a', '', true],
          ['b', '', true],
        ]);
      });

      it('should support key and value names with dash', () => {
        const bindings = parseTemplateBindings('*key="let i-a = j-a,"');
        expect(humanize(bindings)).toEqual([
          // [ key, value, VariableBinding ]
          ['key', null, false],
          ['i-a', 'j-a', true],
        ]);
      });

      it('should support declarations with or without value assignment', () => {
        const bindings = parseTemplateBindings('*key="let item; let i = k"');
        expect(humanize(bindings)).toEqual([
          // [ key, value, VariableBinding ]
          ['key', null, false],
          ['item', null, true],
          ['i', 'k', true],
        ]);
      });

      it('should support declaration before an expression', () => {
        const bindings = parseTemplateBindings('*directive="let item in expr; let a = b"');
        expect(humanize(bindings)).toEqual([
          // [ key, value, VariableBinding ]
          ['directive', null, false],
          ['item', null, true],
          ['directiveIn', 'expr', false],
          ['a', 'b', true],
        ]);
      });
    });

    describe('"as" binding', () => {
      it('should support single declaration', () => {
        const bindings = parseTemplateBindings('*ngIf="exp as local"');
        expect(humanize(bindings)).toEqual([
          // [ key, value, VariableBinding ]
          ['ngIf', 'exp', false],
          ['local', 'ngIf', true],
        ]);
      });

      it('should support declaration after an expression', () => {
        const bindings = parseTemplateBindings('*ngFor="let item of items as iter; index as i"');
        expect(humanize(bindings)).toEqual([
          // [ key, value, VariableBinding ]
          ['ngFor', null, false],
          ['item', null, true],
          ['ngForOf', 'items', false],
          ['iter', 'ngForOf', true],
          ['i', 'index', true],
        ]);
      });

      it('should support key and value names with dash', () => {
        const bindings = parseTemplateBindings('*key="foo, k-b as l-b;"');
        expect(humanize(bindings)).toEqual([
          // [ key, value, VariableBinding ]
          ['key', 'foo', false],
          ['l-b', 'k-b', true],
        ]);
      });
    });

    describe('source, key, value spans', () => {
      it('should map empty expression', () => {
        const attr = '*ngIf=""';
        const bindings = parseTemplateBindings(attr);
        expect(humanizeSpans(bindings, attr)).toEqual([
          // source span, key span, value span
          ['ngIf="', 'ngIf', null],
        ]);
      });

      it('should map variable declaration via "let"', () => {
        const attr = '*key="let i"';
        const bindings = parseTemplateBindings(attr);
        expect(humanizeSpans(bindings, attr)).toEqual([
          // source span, key span, value span
          ['key="', 'key', null],  // source span stretches till next binding
          ['let i', 'i', null],
        ]);
      });

      it('shoud map multiple variable declarations via "let"', () => {
        const attr = '*key="let item; let i=index; let e=even;"';
        const bindings = parseTemplateBindings(attr);
        expect(humanizeSpans(bindings, attr)).toEqual([
          // source span, key span, value span
          ['key="', 'key', null],
          ['let item; ', 'item', null],
          ['let i=index; ', 'i', 'index'],
          ['let e=even;', 'e', 'even'],
        ]);
      });

      it('shoud map expression with pipe', () => {
        const attr = '*ngIf="cond | pipe as foo, let x; ngIf as y"';
        const bindings = parseTemplateBindings(attr);
        expect(humanizeSpans(bindings, attr)).toEqual([
          // source span, key span, value span
          ['ngIf="cond | pipe ', 'ngIf', 'cond | pipe'],
          ['ngIf="cond | pipe as foo, ', 'foo', 'ngIf'],
          ['let x; ', 'x', null],
          ['ngIf as y', 'y', 'ngIf'],
        ]);
      });

      it('should map variable declaration via "as"', () => {
        const attr =
            '*ngFor="let item; of items | slice:0:1 as collection, trackBy: func; index as i"';
        const bindings = parseTemplateBindings(attr);
        expect(humanizeSpans(bindings, attr)).toEqual([
          // source span, key span, value span
          ['ngFor="', 'ngFor', null],
          ['let item; ', 'item', null],
          ['of items | slice:0:1 ', 'of', 'items | slice:0:1'],
          ['of items | slice:0:1 as collection, ', 'collection', 'of'],
          ['trackBy: func; ', 'trackBy', 'func'],
          ['index as i', 'i', 'index'],
        ]);
      });

      it('should map literal array', () => {
        const attr = '*ngFor="let item, of: [1,2,3] | pipe as items; let i=index, count as len, "';
        const bindings = parseTemplateBindings(attr);
        expect(humanizeSpans(bindings, attr)).toEqual([
          // source span, key span, value span
          ['ngFor="', 'ngFor', null],
          ['let item, ', 'item', null],
          ['of: [1,2,3] | pipe ', 'of', '[1,2,3] | pipe'],
          ['of: [1,2,3] | pipe as items; ', 'items', 'of'],
          ['let i=index, ', 'i', 'index'],
          ['count as len,', 'len', 'count'],
        ]);
      });
    });
  });

  describe('parseInterpolation', () => {
    it('should return null if no interpolation', () => {
      expect(parseInterpolation('nothing')).toBe(null);
    });

    it('should parse no prefix/suffix interpolation', () => {
      const ast = parseInterpolation('{{a}}')!.ast as Interpolation;
      expect(ast.strings).toEqual(['', '']);
      expect(ast.expressions.length).toEqual(1);
      expect(ast.expressions[0].name).toEqual('a');
    });

    it('should parse prefix/suffix with multiple interpolation', () => {
      const originalExp = 'before {{ a }} middle {{ b }} after';
      const ast = parseInterpolation(originalExp)!.ast;
      expect(unparse(ast)).toEqual(originalExp);
      validate(ast);
    });

    it('should report empty interpolation expressions', () => {
      expectError(
          parseInterpolation('{{}}')!, 'Blank expressions are not allowed in interpolated strings');

      expectError(
          parseInterpolation('foo {{  }}')!,
          'Parser Error: Blank expressions are not allowed in interpolated strings');
    });

    it('should parse conditional expression', () => {
      checkInterpolation('{{ a < b ? a : b }}');
    });

    it('should parse expression with newline characters', () => {
      checkInterpolation(`{{ 'foo' +\n 'bar' +\r 'baz' }}`, `{{ "foo" + "bar" + "baz" }}`);
    });

    it('should support custom interpolation', () => {
      const parser = new Parser(new Lexer());
      const ast =
          parser.parseInterpolation('{% a %}', null, 0, {start: '{%', end: '%}'})!.ast as any;
      expect(ast.strings).toEqual(['', '']);
      expect(ast.expressions.length).toEqual(1);
      expect(ast.expressions[0].name).toEqual('a');
    });

    describe('comments', () => {
      it('should ignore comments in interpolation expressions', () => {
        checkInterpolation('{{a //comment}}', '{{ a }}');
      });

      it('should retain // in single quote strings', () => {
        checkInterpolation(`{{ 'http://www.google.com' }}`, `{{ "http://www.google.com" }}`);
      });

      it('should retain // in double quote strings', () => {
        checkInterpolation(`{{ "http://www.google.com" }}`, `{{ "http://www.google.com" }}`);
      });

      it('should ignore comments after string literals', () => {
        checkInterpolation(`{{ "a//b" //comment }}`, `{{ "a//b" }}`);
      });

      it('should retain // in complex strings', () => {
        checkInterpolation(
            `{{"//a\'//b\`//c\`//d\'//e" //comment}}`, `{{ "//a\'//b\`//c\`//d\'//e" }}`);
      });

      it('should retain // in nested, unterminated strings', () => {
        checkInterpolation(`{{ "a\'b\`" //comment}}`, `{{ "a\'b\`" }}`);
      });
    });
  });

  describe('parseSimpleBinding', () => {
    it('should parse a field access', () => {
      const p = parseSimpleBinding('name');
      expect(unparse(p)).toEqual('name');
      validate(p);
    });

    it('should report when encountering pipes', () => {
      expectError(
          validate(parseSimpleBinding('a | somePipe')),
          'Host binding expression cannot contain pipes');
    });

    it('should report when encountering interpolation', () => {
      expectError(
          validate(parseSimpleBinding('{{exp}}')),
          'Got interpolation ({{}}) where expression was expected');
    });

    it('should report when encountering field write', () => {
      expectError(validate(parseSimpleBinding('a = b')), 'Bindings cannot contain assignments');
    });
  });

  describe('wrapLiteralPrimitive', () => {
    it('should wrap a literal primitive', () => {
      expect(unparse(validate(createParser().wrapLiteralPrimitive('foo', null, 0))))
          .toEqual('"foo"');
    });
  });

  describe('error recovery', () => {
    function recover(text: string, expected?: string) {
      const expr = validate(parseAction(text));
      expect(unparse(expr)).toEqual(expected || text);
    }
    it('should be able to recover from an extra paren', () => recover('((a)))', 'a'));
    it('should be able to recover from an extra bracket', () => recover('[[a]]]', '[[a]]'));
    it('should be able to recover from a missing )', () => recover('(a;b', 'a; b;'));
    it('should be able to recover from a missing ]', () => recover('[a,b', '[a, b]'));
    it('should be able to recover from a missing selector', () => recover('a.'));
    it('should be able to recover from a missing selector in a array literal',
       () => recover('[[a.], b, c]'));
  });

  describe('offsets', () => {
    it('should retain the offsets of an interpolation', () => {
      const interpolations = splitInterpolation('{{a}}  {{b}}  {{c}}')!;
      expect(interpolations.offsets).toEqual([2, 9, 16]);
    });

    it('should retain the offsets into the expression AST of interpolations', () => {
      const source = parseInterpolation('{{a}}  {{b}}  {{c}}')!;
      const interpolation = source.ast as Interpolation;
      expect(interpolation.expressions.map(e => e.span.start)).toEqual([2, 9, 16]);
    });
  });
});

function createParser() {
  return new Parser(new Lexer());
}

function parseAction(text: string, location: any = null, offset: number = 0): ASTWithSource {
  return createParser().parseAction(text, location, offset);
}

function parseBinding(text: string, location: any = null, offset: number = 0): ASTWithSource {
  return createParser().parseBinding(text, location, offset);
}

function parseTemplateBindings(attribute: string, templateUrl = 'foo.html'): TemplateBinding[] {
  const match = attribute.match(/^\*(.+)="(.*)"$/);
  expect(match).toBeTruthy(`failed to extract key and value from ${attribute}`);
  const [_, key, value] = match;
  const absKeyOffset = 1;  // skip the * prefix
  const absValueOffset = attribute.indexOf('=') + '="'.length;
  const parser = createParser();
  const result =
      parser.parseTemplateBindings(key, value, templateUrl, absKeyOffset, absValueOffset);
  expect(result.errors).toEqual([]);
  expect(result.warnings).toEqual([]);
  return result.templateBindings;
}

function parseInterpolation(text: string, location: any = null, offset: number = 0): ASTWithSource|
    null {
  return createParser().parseInterpolation(text, location, offset);
}

function splitInterpolation(text: string, location: any = null): SplitInterpolation|null {
  return createParser().splitInterpolation(text, location);
}

function parseSimpleBinding(text: string, location: any = null, offset: number = 0): ASTWithSource {
  return createParser().parseSimpleBinding(text, location, offset);
}

function checkInterpolation(exp: string, expected?: string) {
  const ast = parseInterpolation(exp)!;
  if (expected == null) expected = exp;
  expect(unparse(ast)).toEqual(expected);
  validate(ast);
}

function checkBinding(exp: string, expected?: string) {
  const ast = parseBinding(exp);
  if (expected == null) expected = exp;
  expect(unparse(ast)).toEqual(expected);
  validate(ast);
}

function checkAction(exp: string, expected?: string) {
  const ast = parseAction(exp);
  if (expected == null) expected = exp;
  expect(unparse(ast)).toEqual(expected);
  validate(ast);
}

function expectError(ast: {errors: ParserError[]}, message: string) {
  for (const error of ast.errors) {
    if (error.message.indexOf(message) >= 0) {
      return;
    }
  }
  const errMsgs = ast.errors.map(err => err.message).join('\n');
  throw Error(
      `Expected an error containing "${message}" to be reported, but got the errors:\n` + errMsgs);
}

function expectActionError(text: string, message: string) {
  expectError(validate(parseAction(text)), message);
}

function expectBindingError(text: string, message: string) {
  expectError(validate(parseBinding(text)), message);
}