Allow omitting var name in nest parser

Author: keichi

lib/binary_parser.js

@@ -170,12 +170,14 @@ Parser.prototype.choice = function(varName, options) {
     options = varName;
     varName = null;
   }
+
   if (!options.tag) {
     throw new Error("Tag option of array is not defined.");
   }
   if (!options.choices) {
     throw new Error("Choices option of array is not defined.");
   }
+
   Object.keys(options.choices).forEach(function(key) {
     if (isNaN(parseInt(key, 10))) {
       throw new Error("Key of choices must be a number.");
@@ -203,13 +205,22 @@ Parser.prototype.choice = function(varName, options) {
 };
 
 Parser.prototype.nest = function(varName, options) {
+  if (arguments.length == 1 && typeof varName === "object") {
+    options = varName;
+    varName = null;
+  }
+
   if (!options.type) {
     throw new Error("Type option of nest is not defined.");
   }
-
   if (!(options.type instanceof Parser) && !aliasRegistry[options.type]) {
     throw new Error("Type option of nest must be a Parser object.");
   }
+  if (!(options.type instanceof Parser) && !varName) {
+    throw new Error(
+      "options.type must be a object if variable name is omitted."
+    );
+  }
 
   return this.setNextParser("nest", varName, options);
 };
@@ -701,8 +712,11 @@ Parser.prototype.generateChoice = function(ctx) {
 
 Parser.prototype.generateNest = function(ctx) {
   var nestVar = ctx.generateVariable(this.varName);
+
   if (this.options.type instanceof Parser) {
-    ctx.pushCode("{0} = {};", nestVar);
+    if (this.varName) {
+      ctx.pushCode("{0} = {};", nestVar);
+    }
     ctx.pushPath(this.varName);
     this.options.type.generate(ctx);
     ctx.popPath(this.varName);

test/composite_parser.js

@@ -882,6 +882,28 @@ describe("Composite parser", function() {
         name: "John Doe"
       });
     });
+
+    it("should 'flatten' output when using null varName", function() {
+      var parser = new Parser()
+        .string("s1", { zeroTerminated: true })
+        .nest(null, {
+          type: new Parser().string("s2", { zeroTerminated: true })
+        });
+
+      var buf = Buffer.from("foo\0bar\0");
+
+      assert.deepEqual(parser.parse(buf), { s1: "foo", s2: "bar" });
+    });
+
+    it("should 'flatten' output when omitting varName", function() {
+      var parser = new Parser().string("s1", { zeroTerminated: true }).nest({
+        type: new Parser().string("s2", { zeroTerminated: true })
+      });
+
+      var buf = Buffer.from("foo\0bar\0");
+
+      assert.deepEqual(parser.parse(buf), { s1: "foo", s2: "bar" });
+    });
   });
 
   describe("Buffer parser", function() {