feat: Turn off the prettier/prettier rule if found

We already run prettier, so there's no need for eslint-plugin-prettier to run.

src/__tests__/utils.js

@@ -246,6 +246,29 @@ test("eslint max-len.tabWidth value should be used for tabWidth when tabs are us
   });
 });
 
+test("Turn off prettier/prettier rule if found, but still infer options from it", () => {
+  const { eslint, prettier } = getOptionsForFormatting({
+    rules: {
+      "prettier/prettier": [
+        2,
+        {
+          trailingComma: "all"
+        }
+      ]
+    }
+  });
+
+  expect(eslint).toMatchObject({
+    rules: {
+      "prettier/prettier": ["off"]
+    }
+  });
+
+  expect(prettier).toMatchObject({
+    trailingComma: "all"
+  });
+});
+
 test("eslint config has only necessary properties", () => {
   const { eslint } = getOptionsForFormatting({
     globals: ["window:false"],

src/utils.js

@@ -64,12 +64,22 @@ function getOptionsForFormatting(
   prettierOptions = {},
   fallbackPrettierOptions = {}
 ) {
-  const eslint = getRelevantESLintConfig(eslintConfig);
+  let eslint = getRelevantESLintConfig(eslintConfig);
   const prettier = getPrettierOptionsFromESLintRules(
     eslintConfig,
     prettierOptions,
     fallbackPrettierOptions
   );
+
+  // Disable "prettier/prettier", we don't need to run prettier twice
+  eslint = {
+    ...eslint,
+    rules: {
+      ...eslint.rules,
+      "prettier/prettier": ["off"]
+    }
+  };
+
   return { eslint, prettier };
 }