javascript - 如何检测分号是否用于终止由 Esprima 生成的 Mozilla Parser AST 中的表达式？

Question

开发人员创建了一个非常简单的程序：

var a = 6;
var b = 7
console.log(a * b);

我想确保开发人员使用分号，因为我不相信所有开发人员都知道所有ASI规则。由于我将添加其他代码质量检查，因此我想使用Esprima生成要检查的代码的AST 。当使用Esprima 在线解析器解析上面的简单程序时（选中“基于行和列”选项），将创建以下结构：

{
    "loc": {
        "start": {
            "line": 1,
            "column": 0
        },
        "end": {
            "line": 3,
            "column": 19
        }
    },
    "type": "Program",
    "body": [
        {
            "loc": {
                "start": {
                    "line": 1,
                    "column": 0
                },
                "end": {
                    "line": 1,
                    "column": 10
                }
            },
            "type": "VariableDeclaration",
            "declarations": [
                {
                    "loc": {
                        "start": {
                            "line": 1,
                            "column": 4
                        },
                        "end": {
                            "line": 1,
                            "column": 9
                        }
                    },
                    "type": "VariableDeclarator",
                    "id": {
                        "loc": {
                            "start": {
                                "line": 1,
                                "column": 4
                            },
                            "end": {
                                "line": 1,
                                "column": 5
                            }
                        },
                        "type": "Identifier",
                        "name": "a"
                    },
                    "init": {
                        "loc": {
                            "start": {
                                "line": 1,
                                "column": 8
                            },
                            "end": {
                                "line": 1,
                                "column": 9
                            }
                        },
                        "type": "Literal",
                        "value": 6,
                        "raw": "6"
                    }
                }
            ],
            "kind": "var"
        },
        {
            "loc": {
                "start": {
                    "line": 2,
                    "column": 0
                },
                "end": {
                    "line": 3,
                    "column": 0
                }
            },
            "type": "VariableDeclaration",
            "declarations": [
                {
                    "loc": {
                        "start": {
                            "line": 2,
                            "column": 4
                        },
                        "end": {
                            "line": 2,
                            "column": 9
                        }
                    },
                    "type": "VariableDeclarator",
                    "id": {
                        "loc": {
                            "start": {
                                "line": 2,
                                "column": 4
                            },
                            "end": {
                                "line": 2,
                                "column": 5
                            }
                        },
                        "type": "Identifier",
                        "name": "b"
                    },
                    "init": {
                        "loc": {
                            "start": {
                                "line": 2,
                                "column": 8
                            },
                            "end": {
                                "line": 2,
                                "column": 9
                            }
                        },
                        "type": "Literal",
                        "value": 7,
                        "raw": "7"
                    }
                }
            ],
            "kind": "var"
        },
        {
            "loc": {
                "start": {
                    "line": 3,
                    "column": 0
                },
                "end": {
                    "line": 3,
                    "column": 19
                }
            },
            "type": "ExpressionStatement",
            "expression": {
                "loc": {
                    "start": {
                        "line": 3,
                        "column": 0
                    },
                    "end": {
                        "line": 3,
                        "column": 18
                    }
                },
                "type": "CallExpression",
                "callee": {
                    "loc": {
                        "start": {
                            "line": 3,
                            "column": 0
                        },
                        "end": {
                            "line": 3,
                            "column": 11
                        }
                    },
                    "type": "MemberExpression",
                    "computed": false,
                    "object": {
                        "loc": {
                            "start": {
                                "line": 3,
                                "column": 0
                            },
                            "end": {
                                "line": 3,
                                "column": 7
                            }
                        },
                        "type": "Identifier",
                        "name": "console"
                    },
                    "property": {
                        "loc": {
                            "start": {
                                "line": 3,
                                "column": 8
                            },
                            "end": {
                                "line": 3,
                                "column": 11
                            }
                        },
                        "type": "Identifier",
                        "name": "log"
                    }
                },
                "arguments": [
                    {
                        "loc": {
                            "start": {
                                "line": 3,
                                "column": 12
                            },
                            "end": {
                                "line": 3,
                                "column": 17
                            }
                        },
                        "type": "BinaryExpression",
                        "operator": "*",
                        "left": {
                            "loc": {
                                "start": {
                                    "line": 3,
                                    "column": 12
                                },
                                "end": {
                                    "line": 3,
                                    "column": 13
                                }
                            },
                            "type": "Identifier",
                            "name": "a"
                        },
                        "right": {
                            "loc": {
                                "start": {
                                    "line": 3,
                                    "column": 16
                                },
                                "end": {
                                    "line": 3,
                                    "column": 17
                                }
                            },
                            "type": "Identifier",
                            "name": "b"
                        }
                    }
                ]
            }
        }
    ]
}

我应该如何检查是否使用了分号？我可以推断出一个可能没有在第二行使用，因为VariableDeclarationAST 中的第二个显示它结束于{line: 3, column: 0}如下所示。

这是使用 Esprima 的其他工具的方式吗？检查\r\nvs\n行尾呢？Esprima 不适合这项任务吗？

编辑

与我分享这个问题的一位同事告诉我，我“可能需要解析树”，这样我就可以获得令牌列表。所以这解决了我的部分问题。以下是 Esprima 提供的代币：

[
{
    "type": "Keyword",
    "value": "var"
},
{
    "type": "Identifier",
    "value": "a"
},
{
    "type": "Punctuator",
    "value": "="
},
{
    "type": "Numeric",
    "value": "6"
},
{
    "type": "Punctuator",
    "value": ";"
},
{
    "type": "Keyword",
    "value": "var"
},
{
    "type": "Identifier",
    "value": "b"
},
{
    "type": "Punctuator",
    "value": "="
},
{
    "type": "Numeric",
    "value": "7"
},
{
    "type": "Identifier",
    "value": "console"
},
{
    "type": "Punctuator",
    "value": "."
},
{
    "type": "Identifier",
    "value": "log"
},
{
    "type": "Punctuator",
    "value": "("
},
{
    "type": "Identifier",
    "value": "a"
},
{
    "type": "Punctuator",
    "value": "*"
},
{
    "type": "Identifier",
    "value": "b"
},
{
    "type": "Punctuator",
    "value": ")"
},
{
    "type": "Punctuator",
    "value": ";"
}
]

现在我需要弄清楚如何将此标记列表与 AST 结合使用，以告诉我应该在第 2 行使用分号。

Answer 1

要捕获 JavaScript 解释器不会捕获的逻辑或协议错误（例如，总是用分号终止语句），您应该编写自己的状态机来为语法建模。对于您给出的示例，这是 CoffeeScript + Node.js 中的一种方法：

esprima = require 'esprima'

p_type = (is_valid) -> (token) -> is_valid(token.type)
p_value = (is_valid) -> (token) -> is_valid(token.value)

p_is = (target) -> (value) -> value is target
p_in = (targets...) -> (value) -> targets.indexOf(value) >= 0
p_tautology = () -> true

p_disjoin = (fs...) ->
  switch fs.length
    when 0
      p_tautology
    when 1
      [f] = fs
      (value) -> f(value)
    when 2
      [f, g] = fs
      (value) -> f(value) || g(value)
    else
      [f, gs...] = fs
      g = p_disjoin.apply(null, gs)
      (value) -> f(value) || g(value)

p_conjoin = (fs...) ->
  switch fs.length
    when 0
      p_tautology
    when 1
      [f] = fs
      (value) -> f(value)
    when 2
      [f, g] = fs
      (value) -> f(value) && g(value)
    else
      [f, gs...] = fs
      g = p_conjoin.apply(null, gs)
      (value) -> f(value) && g(value)

f_type = (token) -> token.type
f_value = (token) -> token.value
f_constant = (value) -> () -> value
f_identity = (x) -> x
f_token = (fn) -> (token) -> fn(token)
f_transition = (dispatch, transition) -> (token) -> transition[dispatch token]
f_default = (default_value, transition_fn) -> (token) -> transition_fn(token) || default_value

to_string = (value) ->
  if value is null
    'null'
  else if value is `undefined`
    'undefined'
  else if typeof value is 'string'
    '"' + value + '"'
  else if typeof value.length is 'number' and value.length >= 0
    elems = []
    for e in value
      elems.push to_string(e)
    '[' + elems.join(', ') + ']'
  else if typeof value is 'object'
    if value.toString is Object::toString
      attrs = []
      for own k,v of value
        attrs.push k + ': ' + to_string(v)
      '{' + attrs.join(', ') + '}'
    else
      value.toString()
  else
    value.toString()

root =
  is_valid: p_disjoin(
    p_conjoin(p_type(p_is 'Keyword'), p_value(p_is 'var')),
    p_type(p_is 'Identifier')
  )
  next_label: f_transition f_type, 'Keyword': 'variable_declaration', 'Identifier': 'identifier'
  handle_error: (tokens, index) ->
    if index > 0
      [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
      {line, column} = prev_token.loc.end
      process.stderr.write(
        "[Error] line #{line}, column #{1 + column}: Expected variable "+
        "declaration after #{to_string prev_token.value}, but received "+
        "#{to_string curr_token.value}\n")
      process.exit(1)
    else
      curr_token = tokens[index]
      {line, column} = curr_token.loc.start
      process.stderr.write(
        "[Error] line #{line}, column #{1 + column}: Expected variable "+
        "declaration but received #{to_string curr_token.value}\n")
      process.exit(1)
  transition:
    identifier: () ->
      is_valid: p_conjoin p_type(p_is 'Punctuator'), p_value(p_in '.')
      next_label: f_transition f_value, '.': 'membership'
      handle_error: (tokens, index) ->
        [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
        {line, column} = prev_token.loc.end
        process.stderr.write(
          "[Error] line #{line}, column #{1 + column}: Expected '.' after "+
          "#{to_string prev_token.value}, but received #{to_string curr_token.value}\n")
        process.exit(1)
      transition:
        membership: () ->
          is_valid: p_type(p_is 'Identifier')
          next_label: f_constant 'invocation'
          handle_error: (tokens, index) ->
            [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
            {line, column} = prev_token.loc.end
            process.stderr.write(
              "[Error] line #{line}, column #{1 + column}: Expected an identifier "+
              "after #{to_string prev_token.value}, but received "+
              "#{to_string curr_token.value}\n")
            process.exit(1)
          transition:
            invocation: () ->
              is_valid: p_conjoin p_type(p_is 'Punctuator'), p_value(p_is '(')
              next_label: f_constant 'identifier'
              handle_error: (tokens, index) ->
                [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
                {line, column} = prev_token.loc.end
                process.stderr.write(
                  "[Error] line #{line}, column #{1 + column}: Expected '(' after "+
                  "#{to_string prev_token.value}, but received "+
                  "#{to_string curr_token.value}\n")
                process.exit(1)
              transition:
                identifier: () ->
                  is_valid: p_type(p_in 'Identifier')
                  next_label: f_constant 'punctuator'
                  handle_error: (tokens, index) ->
                    [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
                    {line, column} = prev_token.loc.end
                    process.stderr.write(
                      "[Error] line #{line}, column #{1 + column}: Expected "+
                      "an identifier after #{to_string prev_token.value}, "+
                      "but received #{to_string curr_token.value}\n")
                    process.exit(1)
                  transition:
                    punctuator: () ->
                      is_valid: p_conjoin p_type(p_is 'Punctuator'), p_value(p_in '*')
                      next_label: f_transition f_value, '*': 'identifier'
                      handle_error: (tokens, index) ->
                        [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
                        {line, column} = prev_token.loc.end
                        process.stderr.write(
                          "[Error] line #{line}, column #{1 + column}: "+
                          "Expected a binary operator after "+
                          "#{to_string prev_token.value}, but received "+
                          "#{to_string curr_token.value}\n")
                        process.exit(1)
                      transition:
                        identifier: () ->
                          is_valid: p_conjoin p_type(p_is 'Identifier')
                          next_label: f_constant 'punctuator'
                          handle_error: (tokens, index) ->
                            [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
                            {line, column} = prev_token.loc.end
                            process.stderr.write(
                              "[Error] line #{line}, column #{1 + column}: Expected "+
                              "an identifier after #{to_string prev_token.value}, "+
                              "but received #{to_string curr_token.value}\n")
                            process.exit(1)
                          transition:
                            punctuator: () ->
                              is_valid: p_conjoin p_type(p_is 'Punctuator'), p_value(p_is ')')
                              next_label: f_constant 'punctuator'
                              handle_error: (tokens, index) ->
                                [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
                                {line, column} = prev_token.loc.end
                                process.stderr.write(
                                  "[Error] line #{line}, column #{1 + column}: "+
                                  "Expected ')' after #{to_string prev_token.value}, "+
                                  "but received #{to_string curr_token.value}\n")
                                process.exit(1)
                              transition:
                                punctuator: () ->
                                  is_valid: f_constant p_type(p_is 'Punctuator'), p_value(p_is ';')
                                  next_label: f_transition f_value, ';': 'terminator'
                                  handle_error: (tokens, index) ->
                                    [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
                                    {line, column} = prev_token.loc.end
                                    process.stderr.write(
                                      "[Error] line #{line}, column #{1 + column}: "+
                                      "Expected ';' after #{to_string prev_token.value}, "+
                                      "but received #{to_string curr_token.value}\n")
                                    process.exit(1)
                                  transition:
                                    terminator: () -> root
    variable_declaration: () ->
      is_valid: p_type(p_is 'Identifier')
      next_label: f_constant 'punctuator'
      handle_error: (tokens, index) ->
        [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
        {line, column} = prev_token.loc.end
        process.stderr.write(
          "[Error] line #{line}, column #{1 + column}: Expected an identifier "+
          "after #{to_string prev_token.value}, but received "+
          "#{to_string curr_token.value}\n")
        process.exit(1)
      transition:
        punctuator: () ->
          is_valid: p_conjoin p_type(p_is 'Punctuator'), p_value(p_in '=', ',', ';')
          next_label: f_token f_transition f_value, '=': 'assignment', ',': 'separator', ';': 'terminator'
          handle_error: (tokens, index) ->
            [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
            {line, column} = prev_token.loc.end
            process.stderr.write(
              "[Error] line #{line}, column #{1 + column}: Expected '=', ',', "+
              "or ';' after #{to_string prev_token.value}, but received "+
              "#{to_string curr_token.value}\n")
            process.exit(1)
          transition:
            assignment: () ->
              is_valid: p_type(p_in 'Boolean', 'Identifier', 'Null', 'Numeric', 'String', 'RegularExpression')
              next_label: f_constant 'punctuator'
              handle_error: (tokens, index) ->
                [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
                {line, column} = prev_token.loc.end
                process.stderr.write(
                  "[Error] line #{line}, column #{1 + column}: Expected a "+
                  "literal or an identifier after #{to_string prev_token.value}, "+
                  "but received #{to_string curr_token.value}\n")
                process.exit(1)
              transition:
                punctuator: () ->
                  is_valid: p_conjoin p_type(p_is 'Punctuator'), p_value(p_in ',', ';', '.', '(', '{')
                  next_label: f_transition f_value, ',': 'identifier', ';': 'terminator'
                  handle_error: (tokens, index) ->
                    [prev_token, curr_token] = tokens.slice(index - 1, index + 1)
                    {line, column} = prev_token.loc.end
                    process.stderr.write(
                      "[Error] line #{line}, column: #{1 + column}: "+
                      "Expected ',' or ';' after #{to_string prev_token.value}, "+
                      "but received #{to_string curr_token.value}\n")
                    process.exit(1)
                  transition:
                    identifier: () -> root.transition.variable_declaration()
                    terminator: () -> root
            separator: () -> root.transition.variable_declaration()
            terminator: () -> root

lint = (tokens) ->
  state = root
  index = 0
  prev_token = null
  while index < tokens.length
    token = tokens[index]
    if state.is_valid(token)
      state = state.transition[state.next_label token]()
    else
      state.handle_error(tokens, index)
    prev_token = token
    index += 1

text = '''
var a = 6;
var b = 7
console.log(a * b);
'''

tokens = esprima.tokenize(text, loc: true)
lint tokens