Improve performance for generator.buffer

packages/babel-generator/src/buffer.js

@@ -14,6 +14,7 @@ export default class Buffer {
     this._indent = format.indent.base;
     this.format = format;
     this.buf = "";
+    this.last = "";
   }
 
   parenPushNewlineState: ?Object;
@@ -191,42 +192,24 @@ export default class Buffer {
       return;
     }
 
-    removeLast = removeLast || false;
-
-    if (typeof i === "number") {
-      i = Math.min(2, i);
-
-      if (this.endsWith("{\n") || this.endsWith(":\n")) i--;
-      if (i <= 0) return;
-
-      while (i > 0) {
-        this._newline(removeLast);
-        i--;
-      }
-      return;
-    }
-
-    if (typeof i === "boolean") {
-      removeLast = i;
-    }
-
-    this._newline(removeLast);
-  }
-
-  /**
-   * Adds a newline unless there is already two previous newlines.
-   */
-
-  _newline(removeLast?: boolean) {
     // never allow more than two lines
     if (this.endsWith("\n\n")) return;
 
+    if (typeof i === "boolean") removeLast = i;
+    if (typeof i !== "number") i = 1;
+
+    i = Math.min(2, i);
+    if (this.endsWith("{\n") || this.endsWith(":\n")) i--;
+    if (i <= 0) return;
+
     // remove the last newline
-    if (removeLast && this.isLast("\n")) this.removeLast("\n");
+    if (removeLast) {
+      this.removeLast("\n");
+    }
 
     this.removeLast(" ");
     this._removeSpacesAfterLastNewline();
-    this._push("\n");
+    this._push(repeating("\n", i));
   }
 
   /**
@@ -235,21 +218,8 @@ export default class Buffer {
 
   _removeSpacesAfterLastNewline() {
     let lastNewlineIndex = this.buf.lastIndexOf("\n");
-    if (lastNewlineIndex === -1) {
-      return;
-    }
-
-    let index = this.buf.length - 1;
-    while (index > lastNewlineIndex) {
-      if (this.buf[index] !== " ") {
-        break;
-      }
-
-      index--;
-    }
-
-    if (index === lastNewlineIndex) {
-      this.buf = this.buf.substring(0, index + 1);
+    if (lastNewlineIndex >= 0 && this.buf.trimRight().length <= lastNewlineIndex) {
+      this.buf = this.buf.substring(0, lastNewlineIndex + 1);
       this.last = "\n";
     }
   }
@@ -310,11 +280,11 @@ export default class Buffer {
    * Test if the buffer ends with a string.
    */
 
-  endsWith(str: string, buf: string = this.buf): boolean {
+  endsWith(str: string): boolean {
     if (str.length === 1) {
-      return buf[buf.length - 1] === str;
+      return this.last === str;
     } else {
-      return buf.slice(-str.length) === str;
+      return this.buf.slice(-str.length) === str;
     }
   }