From 641d459e30ff53a10a6467de413e02bef0320254 Mon Sep 17 00:00:00 2001
From: b1rdfree <378099757@qq.com>
Date: Tue, 28 Aug 2018 20:04:26 +0800
Subject: [PATCH 1/3] Fix null object conversion error in AST node
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

In escodegen.js, converting a null object into source code in AST will generate an error on toString(). This is because the original judgment considers that the null object node has a "value" key value.
Previous code：escodegen.js-----Lines 2310 to 2313：
if (expr.value === null) {return 'null'; }
I think I can change the above code to:
if (expr.raw === 'null' && expr.value===undefined) {return 'null'; }
This way it can be converted from the ast tree to the original code when it encounters a null object normally.
testcase code(Nodejs environment):
var esprima=require("esprima");
var escodegen=require("escodegen");
var ast=esprima.parse("var a=null;");
var code=escodegen.generate(ast);
---
 escodegen.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/escodegen.js b/escodegen.js
index 54e7cfab..5186eecf 100644
--- a/escodegen.js
+++ b/escodegen.js
@@ -2308,7 +2308,7 @@
                 }
             }
 
-            if (expr.value === null) {
+            if (expr.raw === 'null' && expr.value===undefined) {
                 return 'null';
             }
 

From 5d2df844fcd2085cd622a7251ca63abf923d138c Mon Sep 17 00:00:00 2001
From: b1rdfree <378099757@qq.com>
Date: Tue, 28 Aug 2018 20:24:59 +0800
Subject: [PATCH 2/3] Fix null object conversion error in AST node
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

In escodegen.js, converting a null object into source code in AST will generate an error on toString(). This is because the original judgment considers that the null object node has a "value" key value.
Previous code：escodegen.js-----Lines 2310 to 2313：
if (expr.value === null || expr.raw === 'null' && expr.value===undefined) {return 'null'; }
I think I can change the above code to:
if (expr.raw === 'null' && expr.value===undefined) {return 'null'; }
This way it can be converted from the ast tree to the original code when it encounters a null object normally.
testcase code(Nodejs environment):
var esprima=require("esprima");
var escodegen=require("escodegen");
var ast=esprima.parse("var a=null;");
var code=escodegen.generate(ast);
---
 escodegen.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/escodegen.js b/escodegen.js
index 5186eecf..e807fe46 100644
--- a/escodegen.js
+++ b/escodegen.js
@@ -2308,7 +2308,7 @@
                 }
             }
 
-            if (expr.raw === 'null' && expr.value===undefined) {
+            if (expr.value === null || expr.raw === 'null' && expr.value===undefined) {
                 return 'null';
             }
 

From b8908b44356d640b2f84f22a5d82aaf165177d93 Mon Sep 17 00:00:00 2001
From: b1rdfree <378099757@qq.com>
Date: Tue, 28 Aug 2018 21:30:25 +0800
Subject: [PATCH 3/3] Update escodegen.js

---
 escodegen.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/escodegen.js b/escodegen.js
index e807fe46..8e67489a 100644
--- a/escodegen.js
+++ b/escodegen.js
@@ -2308,7 +2308,7 @@
                 }
             }
 
-            if (expr.value === null || expr.raw === 'null' && expr.value===undefined) {
+            if (expr.value === null || (expr.raw === 'null' && expr.value===undefined)) {
                 return 'null';
             }