Avoid unnecessary work during lookahead (#9982)

* Do not call pushComment when doing lookahead * Do no updateContext when doing lookahead * Do not clone contexts anymore
babel · May 16, 2019 · 4da7a01 · 4da7a01
1 parent 47eb1dd
commit 4da7a01
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Showing 2 changed files with 13 additions and 7 deletions.
diff --git a/packages/babel-parser/src/tokenizer/index.js b/packages/babel-parser/src/tokenizer/index.js
@@ -226,11 +226,9 @@ export default class Tokenizer extends LocationParser {
       loc: new SourceLocation(startLoc, endLoc),
     };
 
-    if (!this.isLookahead) {
-      if (this.options.tokens) this.state.tokens.push(comment);
-      this.state.comments.push(comment);
-      this.addComment(comment);
-    }
+    if (this.options.tokens) this.state.tokens.push(comment);
+    this.state.comments.push(comment);
+    this.addComment(comment);
   }
 
   skipBlockComment(): void {
@@ -250,6 +248,10 @@ export default class Tokenizer extends LocationParser {
       this.state.lineStart = match.index + match[0].length;
     }
 
+    // If we are doing a lookahead right now we need to advance the position (above code)
+    // but we do not want to push the comment to the state.
+    if (this.isLookahead) return;
+
     this.pushComment(
       true,
       this.input.slice(start + 2, end),
@@ -276,6 +278,10 @@ export default class Tokenizer extends LocationParser {
       }
     }
 
+    // If we are doing a lookahead right now we need to advance the position (above code)
+    // but we do not want to push the comment to the state.
+    if (this.isLookahead) return;
+
     this.pushComment(
       false,
       this.input.slice(start + startSkip, this.state.pos),
@@ -350,7 +356,7 @@ export default class Tokenizer extends LocationParser {
     this.state.type = type;
     this.state.value = val;
 
-    this.updateContext(prevType);
+    if (!this.isLookahead) this.updateContext(prevType);
   }
 
   // ### Token reading

diff --git a/packages/babel-parser/src/tokenizer/state.js b/packages/babel-parser/src/tokenizer/state.js
@@ -170,7 +170,7 @@ export default class State {
       // $FlowIgnore
       let val = this[key];
 
-      if ((!skipArrays || key === "context") && Array.isArray(val)) {
+      if (!skipArrays && Array.isArray(val)) {
         val = val.slice();
       }