glayzzle#194 - add a preBuild callback helper

Author: ichiriac

src/ast.js

@@ -254,6 +254,9 @@ AST.prototype.prepare = function(kind, docs, parser) {
     let location = null;
     const args = Array.prototype.slice.call(arguments);
     args.push(docs);
+    if (typeof result.preBuild === "function") {
+      result.preBuild(arguments);
+    }
     if (self.withPositions || self.withSource) {
       let src = null;
       if (self.withSource) {
@@ -280,9 +283,13 @@ AST.prototype.prepare = function(kind, docs, parser) {
     if (typeof node !== "function") {
       throw new Error('Undefined node "' + kind + '"');
     }
-    const result = Object.create(node.prototype);
-    node.apply(result, args);
-    return self.resolvePrecedence(result);
+    const astNode = Object.create(node.prototype);
+    node.apply(astNode, args);
+    result.instance = astNode;
+    if (result.trailingComments) {
+      astNode.trailingComments = result.trailingComments;
+    }
+    return self.resolvePrecedence(astNode);
   };
   /**
    * Helper to change a node kind
@@ -291,6 +298,18 @@ AST.prototype.prepare = function(kind, docs, parser) {
   result.setKind = function(newKind) {
     kind = newKind;
   };
+  /**
+   * Sets a list of trailing comments
+   * @param {*} docs
+   */
+  result.setTrailingComments = function(docs) {
+    if (result.instance) {
+      // already created
+      result.instance.trailingComments = docs;
+    } else {
+      result.trailingComments = docs;
+    }
+  };
   /**
    * Release a node without using it on the AST
    */