Fix subtle bug where nested super expressions could result in bad tra…

…nsformed output. This had to do with ensuring edits occur leafs first, root last in the AST. Super assignment expressions were being edited out of turn by invoking the edits on visiting the left side rather than the assignment expression itself, which could cause the parent assignment expression to be edited before the child right side expression is edited - causing overwriting of the output source.
leebyron · Oct 7, 2016 · b1976f2 · b1976f2
1 parent d8e0914
commit b1976f2
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Showing 3 changed files with 53 additions and 31 deletions.
diff --git a/index.js b/index.js
@@ -207,6 +207,9 @@ var asyncToGenVisitor = {
   MemberExpression: {
     leave: leaveMemberExpression
   },
+  AssignmentExpression: {
+    leave: leaveAssignmentExpression
+  },
   ForAwaitStatement: {
     leave: leaveForAwait
   }
@@ -360,16 +363,60 @@ function leaveMemberExpression(editor, node, ast, stack) {
   // Only transform super member expressions.
   if (node.object.type !== 'Super') return;
 
+  var contextNode = stack.parent;
+
+  // Do not transform delete unary or left-hand-side expressions.
+  if (
+    contextNode.operator === 'delete' ||
+    contextNode.type === 'AssignmentExpression' && contextNode.left === node
+  ) return;
+
   // Only within transformed async function scopes.
   var envRecord = currentScope(ast);
   if (!envRecord.async) return;
 
-  var contextNode = stack.parent;
+  envRecord.referencesSuper = true;
+
+  convertSuperMember(editor, node, ast);
+
+  editor.overwrite(node.object.start, node.object.end, '$uper(');
+  editor.insertLeft(node.end, ')');
+
+  // Ensure super.prop() use the current this binding.
+  if (contextNode.type === 'CallExpression') {
+    envRecord.referencesThis = true;
+    var idx = findTokenIndex(ast.tokens, node.end);
+    while (ast.tokens[idx].type.label !== '(') {
+      idx++;
+    }
+    editor.overwrite(ast.tokens[idx].start, ast.tokens[idx].end, contextNode.arguments.length ? '.call(this,' : '.call(this');
+  }
+}
+
+function leaveAssignmentExpression(editor, node, ast, stack) {
+  // Only transform super assignment expressions.
+  var left = node.left;
+  if (left.type !== 'MemberExpression' || left.object.type !== 'Super') return;
+
+  // Only within transformed async function scopes.
+  var envRecord = currentScope(ast);
+  if (!envRecord.async) return;
+
+  envRecord.referencesSuperEq = true;
+
+  convertSuperMember(editor, left, ast);
 
-  // Do not transform delete unary expressions.
-  if (contextNode.operator === 'delete') return;
+  editor.overwrite(left.object.start, left.object.end, '$uperEq(');
+  editor.insertLeft(node.end, ')')
 
-  // Convert member property to function argument
+  var idx = findTokenIndex(ast.tokens, left.end);
+  while (ast.tokens[idx].type.label !== '=') {
+    idx++;
+  }
+  editor.overwrite(ast.tokens[idx].start, ast.tokens[idx].end, ',');
+}
+
+function convertSuperMember(editor, node, ast) {
   var idx = findTokenIndex(ast.tokens, node.object.end);
   while (ast.tokens[idx].type.label !== (node.computed ? '[' : '.')) {
     idx++;
@@ -381,33 +428,6 @@ function leaveMemberExpression(editor, node, ast, stack) {
     editor.insertRight(node.property.start, '"');
     editor.insertLeft(node.property.end, '"');
   }
-
-  // super.prop = value
-  if (contextNode.type === 'AssignmentExpression' && contextNode.left === node) {
-    envRecord.referencesSuperEq = true;
-    editor.overwrite(node.object.start, node.object.end, '$uperEq(');
-    editor.insertRight(contextNode.end, ')')
-
-    var idx = findTokenIndex(ast.tokens, node.end);
-    while (ast.tokens[idx].type.label !== '=') {
-      idx++;
-    }
-    editor.overwrite(ast.tokens[idx].start, ast.tokens[idx].end, ',');
-  } else {
-    envRecord.referencesSuper = true;
-    editor.overwrite(node.object.start, node.object.end, '$uper(');
-    editor.insertLeft(node.end, ')');
-
-    // Ensure super.prop() use the current this binding.
-    if (contextNode.type === 'CallExpression') {
-      envRecord.referencesThis = true;
-      var idx = findTokenIndex(ast.tokens, node.end);
-      while (ast.tokens[idx].type.label !== '(') {
-        idx++;
-      }
-      editor.overwrite(ast.tokens[idx].start, ast.tokens[idx].end, contextNode.arguments.length ? '.call(this,' : '.call(this');
-    }
-  }
 }
 
 function leaveForAwait(editor, node, ast) {

diff --git a/test/expected.js b/test/expected.js
@@ -150,6 +150,7 @@ class SuperDuper extends BaseClass {
   barAsync() {return __async(function*($uper,$uperEq){
     const arg = $uper("arg").call(this)
     $uperEq("arg" , $uper("arg").call(this))
+    $uperEq("arg" , $uper($uperEq("arg" , $uper("arg").call(this))))
 
     $uperEq( /*a*/  /*b*/ "arg" /*c*/ , /*d*/ $uper( /*e*/  /*f*/ "arg")) /*g*/
     $uperEq( /*a*/  /*b*/ arg /*c*/  /*d*/ , /*e*/ $uper( /*f*/  /*g*/ arg /*h*/ )) /*i*/

diff --git a/test/source.js b/test/source.js
@@ -150,6 +150,7 @@ class SuperDuper extends BaseClass {
   async barAsync() {
     const arg = super.arg()
     super.arg = super.arg()
+    super.arg = super[super.arg = super.arg()]
 
     super /*a*/ . /*b*/ arg /*c*/ = /*d*/ super /*e*/ . /*f*/ arg /*g*/
     super /*a*/ [ /*b*/ arg /*c*/ ] /*d*/ = /*e*/ super /*f*/ [ /*g*/ arg /*h*/ ] /*i*/