From bed4374ef1f86275cbb6210a49013bf73ff126f7 Mon Sep 17 00:00:00 2001
From: Simon Fridlund <simon@fridlund.email>
Date: Wed, 20 Dec 2017 02:25:47 +0100
Subject: [PATCH] feat(perf): Remove unfixable rules

ESLint always lint with all rules you provide, even if you call it with the fix command.
It does this to be able to show you information about the rules it could not fix.
We don't display those messages, so we can remove all unfixable rules and allow ESLint to do less work and in turn run faster.
---
 src/utils.js | 43 +++++++++++++++++++++++++------------------
 1 file changed, 25 insertions(+), 18 deletions(-)

diff --git a/src/utils.js b/src/utils.js
index d0db63b0..35c86c12 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -1,5 +1,6 @@
 import { oneLine } from "common-tags";
 import delve from "dlv";
+import { Linter } from "eslint";
 import getLogger from "loglevel-colored-level-prefix";
 
 const logger = getLogger({ prefix: "prettier-eslint" });
@@ -65,7 +66,7 @@ function getOptionsForFormatting(
 ) {
   const eslint = getRelevantESLintConfig(eslintConfig);
   const prettier = getPrettierOptionsFromESLintRules(
-    eslint,
+    eslintConfig,
     prettierOptions,
     fallbackPrettierOptions
   );
@@ -74,31 +75,21 @@ function getOptionsForFormatting(
 
 function getRelevantESLintConfig(eslintConfig) {
   const { rules } = eslintConfig;
-  // TODO: remove rules that are not fixable for perf
-  // this will require we load the config for every rule...
-  // not sure that'll be worth the effort
-  // but we may be able to maintain a manual list of rules that
-  // are definitely not fixable. Which is what we'll do for now...
-  const rulesThatWillNeverBeFixable = [
-    // TODO add more
-    "valid-jsdoc",
-    "global-require",
-    "no-with"
-  ];
+  const fixableRules = getFixableRules(eslintConfig);
 
   logger.debug("reducing eslint rules down to relevant rules only");
-  const relevantRules = Object.keys(rules).reduce(
-    (rulesAccumulator, ruleName) => {
-      if (rulesThatWillNeverBeFixable.indexOf(ruleName) === -1) {
+  const relevantRules = Object.entries(rules).reduce(
+    (rulesAccumulator, [name, rule]) => {
+      if (fixableRules.includes(name)) {
         logger.trace(
           `adding to relevant rules:`,
-          JSON.stringify({ [ruleName]: rules[ruleName] })
+          JSON.stringify({ [name]: rule })
         );
-        rulesAccumulator[ruleName] = rules[ruleName];
+        rulesAccumulator[name] = rule;
       } else {
         logger.trace(
           `omitting from relevant rules:`,
-          JSON.stringify({ [ruleName]: rules[ruleName] })
+          JSON.stringify({ [name]: rule })
         );
       }
       return rulesAccumulator;
@@ -117,6 +108,22 @@ function getRelevantESLintConfig(eslintConfig) {
   };
 }
 
+function getFixableRules(eslintConfig) {
+  const linter = new Linter(eslintConfig);
+  const rules = linter.getRules();
+  const fixableRules = [];
+  for (const [name, rule] of rules) {
+    if (isRuleFixable(rule)) {
+      fixableRules.push(name);
+    }
+  }
+  return fixableRules;
+}
+
+function isRuleFixable({ meta }) {
+  return meta && meta.fixable;
+}
+
 /**
  * This accepts an eslintConfig object and converts
  * it to the `prettier` options object