首先我创建了一个 esprima
AST,然后我想使用 estraverse
删除一个 Node ,最后使用 escodegen
重新生成代码。
但是我得到一个错误。
我正在尝试的代码是:
var esprima = require('esprima');
var estraverse = require('estraverse');
var escodegen = require('escodegen');
(function () {
//build an ast with 2 lines of code
var ast = esprima.parse("console.log('1');\n console.log('2');")
console.log("original code:\n" + escodegen.generate(ast));
console.log();
//change one of the lines, works
ast = estraverse.replace(ast, {
enter: function (node) {
},
leave: function (node) {
if (node.type === esprima.Syntax.CallExpression) {
this.break();
return esprima.parse("console.log('patch');").body[0].expression;
}
}
});
console.log("patched code:\n" + escodegen.generate(ast));
console.log();
//remove one of the lines, error
ast = estraverse.replace(ast, {
enter: function (node) {
},
leave: function (node) {
if (node.type === esprima.Syntax.CallExpression) {
this.break();
return this.remove();
}
}
});
console.log("removed node:\n" + escodegen.generate(ast));
})()
错误轨迹为:
C:\temp\node_modules\escodegen\escodegen.js:2450
type = expr.type || Syntax.Property;
^
TypeError: Cannot read property 'type' of null
at CodeGenerator.generateExpression (C:\temp\node_modules\escodegen\escodegen.js:2450:20)
at CodeGenerator.ExpressionStatement (C:\temp\node_modules\escodegen\escodegen.js:1335:28)
at CodeGenerator.generateStatement (C:\temp\node_modules\escodegen\escodegen.js:2469:33)
at CodeGenerator.Program (C:\temp\node_modules\escodegen\escodegen.js:1717:43)
at CodeGenerator.generateStatement (C:\temp\node_modules\escodegen\escodegen.js:2469:33)
at generateInternal (C:\temp\node_modules\escodegen\escodegen.js:2490:28)
at Object.generate (C:\temp\node_modules\escodegen\escodegen.js:2558:18)
at C:\temp\bug1.js:35:45
at Object.<anonymous> (C:\temp\bug1.js:38:3)
at Module._compile (module.js:570:32)
我做错了什么吗?这是 escodegen
中的错误还是 estraverse
中的错误?
提前致谢。
最佳答案
我放了一个 issue在 github 上,我得到了一个答案,我正在制作一个无效的 AST。
删除 CallExpression 会使他的父 ExpressionStatement 为空,因此无效。解决方案是简单地删除 ExpressionStatement。
此代码按预期工作:
var esprima = require('esprima');
var estraverse = require('estraverse');
var escodegen = require('escodegen');
(function () {
//build an ast with 2 lines of code
var ast = esprima.parse("console.log('1');\n console.log('2');")
console.log("original code:\n" + escodegen.generate(ast));
console.log();
//remove one of the lines, works!
var done = false;
ast = estraverse.replace(ast, {
enter: function (node) {
if (done)
return this.break();
if (node.type === esprima.Syntax.ExpressionStatement) {
done = true;
this.remove();
}
},
leave: function (node) {
if (done)
return this.break();
}
});
console.log("removed node:\n" + escodegen.generate(ast));
})()
输出:
original code:
console.log('1');
console.log('2');
removed node:
console.log('2');
关于javascript - 删除 Node 后使用 escodegen 生成代码时出错,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45398094/