Introduce rule visitor based fixing support.

Author: Robert Jackson

lib/linter.js

@@ -9,16 +9,6 @@ const MAX_AUTOFIX_PASSES = 10;
 const WARNING_SEVERITY = 1;
 const ERROR_SEVERITY = 2;
 
-/**
- * @param {Object} options
- * @param {string} options.source - The source code to fix.
- * @param {Object[]} messages - The lint messages.
- * @returns {string} output - The fixed source.
- */
-function applyFixes(options /* messages */) {
-  return options.source;
-}
-
 function buildErrorMessage(filePath, moduleId, error) {
   let message = {
     fatal: true,
@@ -225,7 +215,7 @@ class Linter {
       shouldVerify = false;
 
       if (iterations < MAX_AUTOFIX_PASSES) {
-        const output = applyFixes(options, messages);
+        const output = this._applyFixes(options, messages);
 
         // let's lint one more time if source was modified
         shouldVerify = output !== currentSource;
@@ -241,6 +231,43 @@ class Linter {
     };
   }
 
+  /**
+   * @param {Object} options
+   * @param {string} options.source - The source code to verify.
+   * @param {string} options.filePath
+   * @param {string} options.moduleId
+   * @param {Object[]} results - The lint messages.
+   *
+   * @returns {string} output - The fixed source.
+   */
+  _applyFixes(options, results) {
+    let fixableIssues = results.filter(r => r.isFixable);
+
+    // nothing to do, bail out
+    if (fixableIssues.length === 0) {
+      return options.source;
+    }
+
+    let currentSource = options.source;
+
+    let pending = this.statusForModule('pending', options.moduleId);
+    let ruleNames = new Set(fixableIssues.map(r => r.rule));
+    for (let ruleName of ruleNames) {
+      let rule = this._buildRule(ruleName, {
+        pending,
+        shouldFix: true,
+        filePath: options.filePath,
+        rawSource: currentSource,
+        fileConfig: getConfigForFile(this.config, options.filePath),
+      });
+
+      let { code } = transform(currentSource, () => rule.getVisitor());
+      currentSource = code;
+    }
+
+    return currentSource;
+  }
+
   /**
    * The main function for the Linter class.  It takes the source code to lint
    * and returns the results.

lib/rules/base.js

@@ -45,6 +45,7 @@ module.exports = class BaseRule {
 
     this.severity = options.defaultSeverity;
     this.results = [];
+    this.mode = options.shouldFix ? 'fix' : 'report';
 
     // To support DOM-scoped configuration instructions, we need to maintain
     // a stack of our configurations so we can restore the previous one when