From 014a7137f474ee97ae95f35de85ab0e948a1a89b Mon Sep 17 00:00:00 2001
From: JoostK <joost.koehoorn@gmail.com>
Date: Sun, 8 Dec 2019 15:21:38 +0100
Subject: [PATCH] perf(compiler): use a shared interpolation regex (#34332)

The template parser has a certain interpolation config associated with
it and builds a regular expression each time it needs to extract the
interpolations from an input string. Since the interpolation config is
typically the default of `{{` and `}}`, the regular expression doesn't
have to be recreated each time. Therefore, this commit creates only a
single regular expression instance that is used for the default
configuration.

In a large compilation unit with big templates, computing the regular
expression took circa 275ms. This change reduces this to effectively
zero.

PR Close #34332
---
 packages/compiler/src/expression_parser/parser.ts | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/packages/compiler/src/expression_parser/parser.ts b/packages/compiler/src/expression_parser/parser.ts
index ca5473b6bb..9e7977a80a 100644
--- a/packages/compiler/src/expression_parser/parser.ts
+++ b/packages/compiler/src/expression_parser/parser.ts
@@ -23,6 +23,15 @@ export class TemplateBindingParseResult {
       public errors: ParserError[]) {}
 }
 
+const defaultInterpolateRegExp = _createInterpolateRegExp(DEFAULT_INTERPOLATION_CONFIG);
+function _getInterpolateRegExp(config: InterpolationConfig): RegExp {
+  if (config === DEFAULT_INTERPOLATION_CONFIG) {
+    return defaultInterpolateRegExp;
+  } else {
+    return _createInterpolateRegExp(config);
+  }
+}
+
 function _createInterpolateRegExp(config: InterpolationConfig): RegExp {
   const pattern = escapeRegExp(config.start) + '([\\s\\S]*?)' + escapeRegExp(config.end);
   return new RegExp(pattern, 'g');
@@ -138,7 +147,7 @@ export class Parser {
       input: string, location: string,
       interpolationConfig: InterpolationConfig = DEFAULT_INTERPOLATION_CONFIG): SplitInterpolation
       |null {
-    const regexp = _createInterpolateRegExp(interpolationConfig);
+    const regexp = _getInterpolateRegExp(interpolationConfig);
     const parts = input.split(regexp);
     if (parts.length <= 1) {
       return null;
@@ -201,7 +210,7 @@ export class Parser {
 
   private _checkNoInterpolation(
       input: string, location: any, interpolationConfig: InterpolationConfig): void {
-    const regexp = _createInterpolateRegExp(interpolationConfig);
+    const regexp = _getInterpolateRegExp(interpolationConfig);
     const parts = input.split(regexp);
     if (parts.length > 1) {
       this._reportError(