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

@@ -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