optimise generator for compact mode

src/babel/generation/buffer.js

@@ -3,6 +3,7 @@ import trimRight from "trim-right";
 import isBoolean from "lodash/lang/isBoolean";
 import includes from "lodash/collection/includes";
 import isNumber from "lodash/lang/isNumber";
+import * as t from "../types";
 
 export default class Buffer {
   constructor(position, format) {
@@ -54,9 +55,10 @@ export default class Buffer {
     this.space();
   }
 
-  space() {
-    if (this.format.compact) return;
-    if (this.buf && !this.isLast(" ") && !this.isLast("\n")) {
+  space(force?) {
+    if (!force && this.format.compact) return;
+
+    if (force || this.buf && !this.isLast(" ") && !this.isLast("\n")) {
       this.push(" ");
     }
   }
@@ -155,8 +157,12 @@ export default class Buffer {
     this.buf += str;
   }
 
-  endsWith(str) {
-    return this.buf.slice(-str.length) === str;
+  endsWith(str, buf = this.buf) {
+    if (str.length === 1) {
+      return buf[buf.length - 1] === str;
+    } else {
+      return buf.slice(-str.length) === str;
+    }
   }
 
   isLast(cha) {

src/babel/generation/generators/expressions.js

@@ -2,19 +2,19 @@ import isNumber from "lodash/lang/isNumber";
 import * as t from "../../types";
 
 export function UnaryExpression(node, print) {
-  var hasSpace = /[a-z]$/.test(node.operator);
+  var needsSpace = /[a-z]$/.test(node.operator);
   var arg = node.argument;
 
   if (t.isUpdateExpression(arg) || t.isUnaryExpression(arg)) {
-    hasSpace = true;
+    needsSpace = true;
   }
 
   if (t.isUnaryExpression(arg) && arg.operator === "!") {
-    hasSpace = false;
+    needsSpace = false;
   }
 
   this.push(node.operator);
-  if (hasSpace) this.push(" ");
+  if (needsSpace) this.push(" ");
   print.plain(node.argument);
 }
 
@@ -83,19 +83,16 @@ export function CallExpression(node, print) {
 
   this.push("(");
 
-  var separator = ",";
-
-  var isPrettyCall = node._prettyCall && !this.format.retainLines;
+  var isPrettyCall = node._prettyCall && !this.format.retainLines && !this.format.compact;
 
+  var separator;
   if (isPrettyCall) {
-    separator += "\n";
+    separator = ",\n";
     this.newline();
     this.indent();
-  } else {
-    separator += " ";
   }
 
-  print.list(node.arguments, { separator: separator });
+  print.list(node.arguments, { separator });
 
   if (isPrettyCall) {
     this.newline();
@@ -141,9 +138,22 @@ export function AssignmentPattern(node, print) {
 export function AssignmentExpression(node, print) {
   // todo: add cases where the spaces can be dropped when in compact mode
   print.plain(node.left);
-  this.push(" ");
+
+  var spaces = node.operator === "in" || node.operator === "instanceof";
+  this.space(spaces);
+
   this.push(node.operator);
-  this.push(" ");
+
+  if (!spaces) {
+    // space is mandatory to avoid outputting <!--
+    // http://javascript.spec.whatwg.org/#comment-syntax
+    spaces = node.operator === "<" &&
+             t.isUnaryExpression(node.right, { prefix: true, operator: "!" }) &&
+             t.isUnaryExpression(node.right.argument, { prefix: true, operator: "--" })
+  }
+
+  this.space(spaces);
+
   print.plain(node.right);
 }
 

src/babel/generation/generators/methods.js

@@ -42,7 +42,7 @@ export function _method(node, print) {
   }
 
   this._params(value, print);
-  this.push(" ");
+  this.space();
   print.plain(value.body);
 }
 

src/babel/generation/generators/statements.js

@@ -190,16 +190,29 @@ export function VariableDeclaration(node, print, parent) {
     }
   }
 
-  var sep = ",";
+  //
+  // use a pretty separator when we aren't in compact mode, have initializers and don't have retainLines on
+  // this will format declarations like:
+  //
+  //   var foo = "bar", bar = "foo";
+  //
+  // into
+  //
+  //   var foo = "bar",
+  //       bar = "foo";
+  //
+
+  var sep;
   if (!this.format.compact && !this.format.concise && hasInits && !this.format.retainLines) {
-    sep += `\n${repeating(" ", node.kind.length + 1)}`;
-  } else {
-    sep += " ";
+    sep = `,\n${repeating(" ", node.kind.length + 1)}`;
   }
 
+  //
+
   print.list(node.declarations, { separator: sep });
 
   if (t.isFor(parent)) {
+    // don't give semicolons to these nodes since they'll be inserted in the parent generator
     if (parent.left === node || parent.init === node) return;
   }
 

src/babel/generation/generators/types.js

@@ -80,7 +80,7 @@ export function ArrayExpression(node, print) {
       // both (all) of the holes.
       this.push(",");
     } else {
-      if (i > 0) this.push(" ");
+      if (i > 0) this.space();
       print.plain(elem);
       if (i < len - 1) this.push(",");
     }

src/babel/generation/index.js

@@ -128,8 +128,7 @@ class CodeGenerator {
     // catch up to this nodes newline if we're behind
     if (node.loc && this.format.retainLines && this.buffer.buf) {
       var needsParens = false;
-      if (!leftParenPrinted && parent &&
-          this.position.line < node.loc.start.line && t.isTerminatorless(parent)) {
+      if (!leftParenPrinted && parent && this.position.line < node.loc.start.line && t.isTerminatorless(parent)) {
         needsParens = true;
         this._push("(");
       }

src/babel/generation/node/printer.js

@@ -18,7 +18,11 @@ export default class NodePrinter {
   }
 
   list(items, opts = {}) {
-    if (opts.separator == null) opts.separator = ", ";
+    if (opts.separator == null) {
+      opts.separator = ",";
+      if (!this.generator.format.compact) opts.separator += " ";
+    }
+
     return this.join(items, opts);
   }
 

src/babel/traversal/path/context.js

@@ -230,6 +230,7 @@ export function unshiftContext(context) {
  */
 
 export function setup(parentPath, container, listKey, key) {
+  this.inList    = !!listKey;
   this.listKey   = listKey;
   this.parentKey = listKey || key;
   this.container = container;

src/babel/traversal/path/index.js

@@ -21,6 +21,7 @@ export default class NodePath {
     this.context            = null;
     this.container          = null;
     this.listKey            = null;
+    this.inList             = false;
     this.parentKey          = null;
     this.key                = null;
     this.node               = null;