feat(compiler): make interpolation symbols configurable (@Component config) (#9367)

closes #9158

modules/@angular/compiler/test/expression_parser/parser_spec.ts

@@ -467,6 +467,14 @@ export function main() {
         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, {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 }}'); });

modules/@angular/compiler/test/expression_parser/unparser.ts

@@ -1,12 +1,15 @@
 import {AST, AstVisitor, Binary, BindingPipe, Chain, Conditional, EmptyExpr, FunctionCall, ImplicitReceiver, Interpolation, KeyedRead, KeyedWrite, LiteralArray, LiteralMap, LiteralPrimitive, MethodCall, PrefixNot, PropertyRead, PropertyWrite, Quote, SafeMethodCall, SafePropertyRead} from '../../src/expression_parser/ast';
 import {StringWrapper, isPresent, isString} from '../../src/facade/lang';
+import {DEFAULT_INTERPOLATION_CONFIG, InterpolationConfig} from '../../src/interpolation_config';
 
 export class Unparser implements AstVisitor {
   private static _quoteRegExp = /"/g;
   private _expression: string;
+  private _interpolationConfig: InterpolationConfig;
 
-  unparse(ast: AST) {
+  unparse(ast: AST, interpolationConfig: InterpolationConfig = DEFAULT_INTERPOLATION_CONFIG) {
     this._expression = '';
+    this._interpolationConfig = interpolationConfig;
     this._visit(ast);
     return this._expression;
   }
@@ -74,9 +77,9 @@ export class Unparser implements AstVisitor {
     for (let i = 0; i < ast.strings.length; i++) {
       this._expression += ast.strings[i];
       if (i < ast.expressions.length) {
-        this._expression += '{{ ';
+        this._expression += `${this._interpolationConfig.start} `;
         this._visit(ast.expressions[i]);
-        this._expression += ' }}';
+        this._expression += ` ${this._interpolationConfig.end}`;
       }
     }
   }