1
{
2
  rules: {
3
    // 代码结尾的分号
4
    semi: 'off', // 值有 `error` 或 `2`、`warn` 或 `1`、`off` 或 `0`
5
    // 字符串的单、双引号
6
    quotes: ['error', 'single'] // 或是以数组的形式来进行配置规则的选项，选项还可以以对象的形式呈现
7
  }
8
}

1
module.exports = {
2
  meta: {
3
    // 包含规则的元数据
4
    // 指示规则的类型，值为 "problem"、"suggestion" 或 "layout"
5
    type: "suggestion",
6

7
    docs: {
8
      // 对 ESLint 核心规则来说是必需的
9
      description: "disallow `with` statements", // 提供规则的简短描述在规则首页展示
29 collapsed lines
10
      // category (string) 指定规则在规则首页处于的分类
11
      recommended: true, // 配置文件中的 "extends": "ESLint:recommended"属性是否启用该规则
12
      url: "https://ESLint.org/docs/rules/no-with", // 指定可以访问完整文档的 url
13
    },
14

15
    // fixable  // 如果没有 fixable 属性，即使规则实现了 fix 功能，ESLint 也不会进行修复。如果规则不是可修复的，就省略 fixable 属性。
16

17
    schema: [], // 指定该选项 这样的 ESLint 可以避免无效的规则配置
18

19
    // deprecated (boolean) 表明规则是已被弃用。如果规则尚未被弃用，你可以省略 deprecated 属性。
20

21
    messages: {
22
      unexpectedWith: "Unexpected use of 'with' statement.",
23
    },
24
  },
25
  // create (function) 返回一个对象，其中包含了 ESLint 在遍历 js 代码的抽象语法树 AST (ESTree 定义的 AST) 时，用来访问节点的方法。
26
  create(context) {
27
    // 如果一个 key 是个节点类型或 selector，在 向下 遍历树时，ESLint 调用 visitor 函数
28
    // 如果一个 key 是个节点类型或 selector，并带有 :exit，在 向上 遍历树时，ESLint 调用 visitor 函数
29
    // 如果一个 key 是个事件名字，ESLint 为代码路径分析调用 handler 函数
30
    // selector 类型可以到 estree 查找
31
    return {
32
      // 入参为节点node
33
      WithStatement(node) {
34
        context.report({ node, messageId: "unexpectedWith" });
35
      },
36
    };
37
  },
38
};

1
{
2
  "name": "eslint",
3
  "bin": {
4
    "eslint": "bin/eslint.js"
5
  },
6
  "scripts": {
7
    // ...
8
  }
9
}

1
// 代码有删减
2
(async function main() {
3
  // 如果在执行的时候带有 --init 参数则进行初始化 eslint 的配置
4
  if (process.argv.includes("--init")) {
5
    // `eslint --init` has been moved to `@eslint/create-config`
6
    console.warn(
7
      "You can also run this command directly using 'npm init @eslint/config'."
8
    );
9

14 collapsed lines
10
    const spawn = require("cross-spawn");
11
    spawn.sync("npm", ["init", "@eslint/config"], {
12
      encoding: "utf8",
13
      stdio: "inherit",
14
    });
15
    return;
16
  }
17

18
  // 没有附带 --init 参数则检查本地代码
19
  process.exitCode = await require("../lib/cli").execute(
20
    process.argv,
21
    process.argv.includes("--stdin") ? await readStdin() : null
22
  );
23
})();

1
const cli = {
2
  /**
3
   * Executes the CLI based on an array of arguments that is passed in.
4
   * @param {string|Array|Object} args The arguments to process.
5
   * @param {string} [text] The text to lint (used for TTY).
6
   * @returns {Promise<number>} The exit code for the operation.
7
   */
8
  async execute(args, text) {
9
    if (Array.isArray(args)) {
136 collapsed lines
10
      debug("CLI args: %o", args.slice(2));
11
    }
12

13
    /** @type {ParsedCLIOptions} */
14
    let options;
15

16
    try {
17
      options = CLIOptions.parse(args);
18
    } catch (error) {
19
      log.error(error.message);
20
      return 2;
21
    }
22

23
    const files = options._;
24
    const useStdin = typeof text === "string";
25

26
    if (options.help) {
27
      log.info(CLIOptions.generateHelp());
28
      return 0;
29
    }
30
    if (options.version) {
31
      log.info(RuntimeInfo.version());
32
      return 0;
33
    }
34
    if (options.envInfo) {
35
      try {
36
        log.info(RuntimeInfo.environment());
37
        return 0;
38
      } catch (err) {
39
        log.error(err.message);
40
        return 2;
41
      }
42
    }
43

44
    if (options.printConfig) {
45
      if (files.length) {
46
        log.error(
47
          "The --print-config option must be used with exactly one file name."
48
        );
49
        return 2;
50
      }
51
      if (useStdin) {
52
        log.error(
53
          "The --print-config option is not available for piped-in code."
54
        );
55
        return 2;
56
      }
57

58
      const engine = new ESLint(translateOptions(options));
59
      const fileConfig = await engine.calculateConfigForFile(
60
        options.printConfig
61
      );
62

63
      log.info(JSON.stringify(fileConfig, null, "  "));
64
      return 0;
65
    }
66

67
    debug(`Running on ${useStdin ? "text" : "files"}`);
68

69
    if (options.fix && options.fixDryRun) {
70
      log.error(
71
        "The --fix option and the --fix-dry-run option cannot be used together."
72
      );
73
      return 2;
74
    }
75
    if (useStdin && options.fix) {
76
      log.error(
77
        "The --fix option is not available for piped-in code; use --fix-dry-run instead."
78
      );
79
      return 2;
80
    }
81
    if (options.fixType && !options.fix && !options.fixDryRun) {
82
      log.error(
83
        "The --fix-type option requires either --fix or --fix-dry-run."
84
      );
85
      return 2;
86
    }
87

88
    const engine = new ESLint(translateOptions(options));
89
    let results;
90

91
    if (useStdin) {
92
      results = await engine.lintText(text, {
93
        filePath: options.stdinFilename,
94
        warnIgnored: true,
95
      });
96
    } else {
97
      results = await engine.lintFiles(files);
98
    }
99

100
    if (options.fix) {
101
      debug("Fix mode enabled - applying fixes");
102
      await ESLint.outputFixes(results);
103
    }
104

105
    let resultsToPrint = results;
106

107
    if (options.quiet) {
108
      debug("Quiet mode enabled - filtering out warnings");
109
      resultsToPrint = ESLint.getErrorResults(resultsToPrint);
110
    }
111

112
    if (
113
      await printResults(
114
        engine,
115
        resultsToPrint,
116
        options.format,
117
        options.outputFile
118
      )
119
    ) {
120
      // Errors and warnings from the original unfiltered results should determine the exit code
121
      const { errorCount, fatalErrorCount, warningCount } =
122
        countErrors(results);
123

124
      const tooManyWarnings =
125
        options.maxWarnings >= 0 && warningCount > options.maxWarnings;
126
      const shouldExitForFatalErrors =
127
        options.exitOnFatalError && fatalErrorCount > 0;
128

129
      if (!errorCount && tooManyWarnings) {
130
        log.error(
131
          "ESLint found too many warnings (maximum: %s).",
132
          options.maxWarnings
133
        );
134
      }
135

136
      if (shouldExitForFatalErrors) {
137
        return 2;
138
      }
139

140
      return errorCount || tooManyWarnings ? 1 : 0;
141
    }
142

143
    return 2;
144
  },
145
};

1
async lintFiles(patterns) {
2
  if (!isNonEmptyString(patterns) && !isArrayOfNonEmptyString(patterns)) {
3
    throw new Error("'patterns' must be a non-empty string or an array of non-empty strings");
4
  }
5
  const { cliEngine } = privateMembersMap.get(this);
6

7
  return processCLIEngineLintReport(
8
    cliEngine,
9
    cliEngine.executeOnFiles(patterns)
2 collapsed lines
10
  );
11
}

1
executeOnFiles(patterns) {
2
  const {
3
      cacheFilePath,
4
      fileEnumerator,
5
      lastConfigArrays,
6
      lintResultCache,
7
      linter,
8
      options: {
9
          allowInlineConfig,
112 collapsed lines
10
          cache,
11
          cwd,
12
          fix,
13
          reportUnusedDisableDirectives
14
      }
15
  } = internalSlotsMap.get(this);
16
  const results = [];
17
  const startTime = Date.now();
18

19
  // Clear the last used config arrays.
20
  lastConfigArrays.length = 0;
21

22
  // Delete cache file; should this do here?
23
  if (!cache) {
24
      try {
25
          fs.unlinkSync(cacheFilePath);
26
      } catch (error) {
27
          const errorCode = error && error.code;
28

29
          // Ignore errors when no such file exists or file system is read only (and cache file does not exist)
30
          if (errorCode !== "ENOENT" && !(errorCode === "EROFS" && !fs.existsSync(cacheFilePath))) {
31
              throw error;
32
          }
33
      }
34
  }
35

36
  // Iterate source code files.
37
  for (const { config, filePath, ignored } of fileEnumerator.iterateFiles(patterns)) {
38
      if (ignored) {
39
          results.push(createIgnoreResult(filePath, cwd));
40
          continue;
41
      }
42

43
      /*
44
        * Store used configs for:
45
        * - this method uses to collect used deprecated rules.
46
        * - `getRules()` method uses to collect all loaded rules.
47
        * - `--fix-type` option uses to get the loaded rule's meta data.
48
        */
49
      if (!lastConfigArrays.includes(config)) {
50
          lastConfigArrays.push(config);
51
      }
52

53
      // Skip if there is cached result.
54
      if (lintResultCache) {
55
          const cachedResult =
56
              lintResultCache.getCachedLintResults(filePath, config);
57

58
          if (cachedResult) {
59
              const hadMessages =
60
                  cachedResult.messages &&
61
                  cachedResult.messages.length > 0;
62

63
              if (hadMessages && fix) {
64
                  debug(`Reprocessing cached file to allow autofix: ${filePath}`);
65
              } else {
66
                  debug(`Skipping file since it hasn't changed: ${filePath}`);
67
                  results.push(cachedResult);
68
                  continue;
69
              }
70
          }
71
      }
72

73
      // Do lint.
74
      const result = verifyText({
75
          text: fs.readFileSync(filePath, "utf8"),
76
          filePath,
77
          config,
78
          cwd,
79
          fix,
80
          allowInlineConfig,
81
          reportUnusedDisableDirectives,
82
          fileEnumerator,
83
          linter
84
      });
85

86
      results.push(result);
87

88
      /*
89
        * Store the lint result in the LintResultCache.
90
        * NOTE: The LintResultCache will remove the file source and any
91
        * other properties that are difficult to serialize, and will
92
        * hydrate those properties back in on future lint runs.
93
        */
94
      if (lintResultCache) {
95
          lintResultCache.setCachedLintResults(filePath, config, result);
96
      }
97
  }
98

99
  // Persist the cache to disk.
100
  if (lintResultCache) {
101
      lintResultCache.reconcile();
102
  }
103

104
  debug(`Linting complete in: ${Date.now() - startTime}ms`);
105
  let usedDeprecatedRules;
106

107
  return {
108
      results,
109
      ...calculateStatsPerRun(results),
110

111
      // Initialize it lazily because CLI and `ESLint` API don't use it.
112
      get usedDeprecatedRules() {
113
          if (!usedDeprecatedRules) {
114
              usedDeprecatedRules = Array.from(
115
                  iterateRuleDeprecationWarnings(lastConfigArrays)
116
              );
117
          }
118
          return usedDeprecatedRules;
119
      }
120
  };
121
}

1
// 默认的ast解析是espree
2
const espree = require("espree");
3

4
let parserName = DEFAULT_PARSER_NAME; // 'espree'
5
let parser = espree;

1
// 1. 创建一个 eventEmitter 实例。是eslint自己实现的很简单的一个事件触发类 on监听 emit触发
2
const emitter = createEmitter();
3

4
// 2. 递归遍历 AST，把节点添加到 nodeQueue。一个node放入两次 A->B->C->...->C->B->A
5
Traverser.traverse(sourceCode.ast, {
6
  enter(node, parent) {
7
    node.parent = parent;
8
    nodeQueue.push({ isEntering: true, node });
9
  },
107 collapsed lines
10
  leave(node) {
11
    nodeQueue.push({ isEntering: false, node });
12
  },
13
  visitorKeys: sourceCode.visitorKeys,
14
});
15

16
// 3. 遍历 rules，调用 rule.create() 拿到事件(selector)映射表，添加事件监听。
17
// （这里的 configuredRules 是我们在 .eslintrc.json 设置的 rules）
18
Object.keys(configuredRules).forEach((ruleId) => {
19
  const severity = ConfigOps.getRuleSeverity(configuredRules[ruleId]);
20

21
  // 通过ruleId拿到每个规则对应的一个对象，里面有两部分 meta & create 见 【编写rule】
22
  const rule = ruleMapper(ruleId);
23

24
  // ....
25

26
  const messageIds = rule.meta && rule.meta.messages;
27
  let reportTranslator = null;
28
  // 这个对象比较重要，会传给 每个规则里的 rule.create函数
29
  const ruleContext = Object.freeze(
30
    Object.assign(Object.create(sharedTraversalContext), {
31
      id: ruleId,
32
      options: getRuleOptions(configuredRules[ruleId]),
33
      // 每个rule的 handler 都会执行这个函数，抛出问题
34
      report(...args) {
35
        if (reportTranslator === null) {
36
          reportTranslator = createReportTranslator({
37
            ruleId,
38
            severity,
39
            sourceCode,
40
            messageIds,
41
            disableFixes,
42
          });
43
        }
44
        const problem = reportTranslator(...args);
45
        // 省略一堆错误校验
46
        // ....
47
        // 省略一堆错误校验
48

49
        // lint的结果
50
        lintingProblems.push(problem);
51
      },
52
    })
53
  );
54
  // 包装了一下，其实就是 执行 rule.create(ruleContext);
55
  // rule.create(ruleContext) 会返回一个对象，key就是事件名称
56
  const ruleListeners = createRuleListeners(rule, ruleContext);
57

58
  /**
59
   * 在错误信息中加入ruleId
60
   * @param {Function} ruleListener 监听到每个node，然后对应的方法rule.create(ruleContext)返回的对象中对应key的value
61
   * @returns {Function} ruleListener wrapped in error handler
62
   */
63
  function addRuleErrorHandler(ruleListener) {
64
    return function ruleErrorHandler(...listenerArgs) {
65
      try {
66
        return ruleListener(...listenerArgs);
67
      } catch (e) {
68
        e.ruleId = ruleId;
69
        throw e;
70
      }
71
    };
72
  }
73

74
  // 遍历 rule.create(ruleContext) 返回的对象，添加事件监听
75
  Object.keys(ruleListeners).forEach((selector) => {
76
    const ruleListener = timing.enabled
77
      ? timing.time(ruleId, ruleListeners[selector]) // 调用process.hrtime()计时
78
      : ruleListeners[selector];
79
    // 对每一个 selector 进行监听，添加 callback
80
    emitter.on(selector, addRuleErrorHandler(ruleListener));
81
  });
82
});
83

84
// 只有顶层node类型是Program才进行代码路径分析
85
const eventGenerator =
86
  nodeQueue[0].node.type === "Program"
87
    ? new CodePathAnalyzer(
88
        new NodeEventGenerator(emitter, {
89
          visitorKeys: sourceCode.visitorKeys,
90
          fallback: Traverser.getKeys,
91
        })
92
      )
93
    : new NodeEventGenerator(emitter, {
94
        visitorKeys: sourceCode.visitorKeys,
95
        fallback: Traverser.getKeys,
96
      });
97

98
// 4. 遍历 nodeQueue，触发当前节点事件的回调。
99
// 这个 nodeQueue 是前面push进所有的node，分为 入口 和 离开
100
nodeQueue.forEach((traversalInfo) => {
101
  currentNode = traversalInfo.node;
102
  try {
103
    if (traversalInfo.isEntering) {
104
      // 调用 NodeEventGenerator 实例里面的函数
105
      // 在这里触发 emitter.emit()
106
      eventGenerator.enterNode(currentNode);
107
    } else {
108
      eventGenerator.leaveNode(currentNode);
109
    }
110
  } catch (err) {
111
    err.currentNode = currentNode;
112
    throw err;
113
  }
114
});
115
// lint的结果
116
return lintingProblems;

1
// 进入节点 把这个node的父节点push进去
2
enterNode(node) {
3
  if (node.parent) {
4
    this.currentAncestry.unshift(node.parent);
5
  }
6
  this.applySelectors(node, false);
7
}
8
// 离开节点
9
leaveNode(node) {
11 collapsed lines
10
  this.applySelectors(node, true);
11
  this.currentAncestry.shift();
12
}
13
// 进入还是离开 都执行的这个函数
14
// 调用这个函数，如果节点匹配，那么就触发事件
15
applySelector(node, selector) {
16
  if (esquery.matches(node, selector.parsedSelector, this.currentAncestry, this.esqueryOptions)) {
17
    // 触发事件，执行 handler
18
    this.emitter.emit(selector.rawSelector, node);
19
  }
20
}