From 7f7dc7c294bd85397a5cebbea22757cb89cc3943 Mon Sep 17 00:00:00 2001
From: Andrew Kushnir <akushnir@google.com>
Date: Sun, 20 Oct 2019 22:14:34 -0700
Subject: [PATCH] perf(ivy): avoid unnecessary i18n pass while processing a
 template (#33284)

Prior to this commit, we always invoked second i18n pass (in case whitespace removal is on, which is a default), even if a given template doesn't contain i18n information. Now we store a flag (that indicates presence of i18n information in a template) during first i18n pass and use it to check whether second pass is needed.

PR Close #33284
---
 .../compiler/src/render3/view/i18n/meta.ts    |  5 +++++
 .../compiler/src/render3/view/template.ts     | 20 ++++++++++---------
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/packages/compiler/src/render3/view/i18n/meta.ts b/packages/compiler/src/render3/view/i18n/meta.ts
index 3fed00ce11..2e10fe02f4 100644
--- a/packages/compiler/src/render3/view/i18n/meta.ts
+++ b/packages/compiler/src/render3/view/i18n/meta.ts
@@ -44,6 +44,9 @@ const setI18nRefs: VisitNodeFn = (htmlNode, i18nNode) => {
  * stored with other element's and attribute's information.
  */
 export class I18nMetaVisitor implements html.Visitor {
+  // whether visited nodes contain i18n information
+  public hasI18nMeta: boolean = false;
+
   // i18n message generation factory
   private _createI18nMessage = createI18nMessageFactory(this.interpolationConfig);
 
@@ -63,6 +66,7 @@ export class I18nMetaVisitor implements html.Visitor {
 
   visitElement(element: html.Element): any {
     if (hasI18nAttrs(element)) {
+      this.hasI18nMeta = true;
       const attrs: html.Attribute[] = [];
       const attrsMeta: {[key: string]: string} = {};
 
@@ -111,6 +115,7 @@ export class I18nMetaVisitor implements html.Visitor {
   visitExpansion(expansion: html.Expansion, currentMessage: i18n.Message|undefined): any {
     let message;
     const meta = expansion.i18n;
+    this.hasI18nMeta = true;
     if (meta instanceof i18n.IcuPlaceholder) {
       // set ICU placeholder name (e.g. "ICU_1"),
       // generated while processing root element contents,
diff --git a/packages/compiler/src/render3/view/template.ts b/packages/compiler/src/render3/view/template.ts
index b06bd05b38..6d2e0d6c6a 100644
--- a/packages/compiler/src/render3/view/template.ts
+++ b/packages/compiler/src/render3/view/template.ts
@@ -1965,19 +1965,21 @@ export function parseTemplate(
   // before we run whitespace removal process, because existing i18n
   // extraction process (ng xi18n) relies on a raw content to generate
   // message ids
-  rootNodes = html.visitAll(
-      new I18nMetaVisitor(interpolationConfig, !preserveWhitespaces, i18nLegacyMessageIdFormat),
-      rootNodes);
+  const i18nMetaVisitor = new I18nMetaVisitor(
+      interpolationConfig, /* keepI18nAttrs */ !preserveWhitespaces, i18nLegacyMessageIdFormat);
+  rootNodes = html.visitAll(i18nMetaVisitor, rootNodes);
 
   if (!preserveWhitespaces) {
     rootNodes = html.visitAll(new WhitespaceVisitor(), rootNodes);
 
-    // run i18n meta visitor again in case we remove whitespaces, because
-    // that might affect generated i18n message content. During this pass
-    // i18n IDs generated at the first pass will be preserved, so we can mimic
-    // existing extraction process (ng xi18n)
-    rootNodes = html.visitAll(
-        new I18nMetaVisitor(interpolationConfig, /* keepI18nAttrs */ false), rootNodes);
+    // run i18n meta visitor again in case whitespaces are removed (because that might affect
+    // generated i18n message content) and first pass indicated that i18n content is present in a
+    // template. During this pass i18n IDs generated at the first pass will be preserved, so we can
+    // mimic existing extraction process (ng xi18n)
+    if (i18nMetaVisitor.hasI18nMeta) {
+      rootNodes = html.visitAll(
+          new I18nMetaVisitor(interpolationConfig, /* keepI18nAttrs */ false), rootNodes);
+    }
   }
 
   const {nodes, errors, styleUrls, styles} = htmlAstToRender3Ast(rootNodes, bindingParser);