Update prettier to v2 (#11579)

Co-authored-by: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

scripts/parser-tests/test262/index.js

@@ -187,9 +187,7 @@ runner
         "The following Features are not currently mapped or ignored:"
       );
       console.log(
-        Array.from(unmappedFeatures)
-          .join("\n")
-          .replace(/^/gm, "   ")
+        Array.from(unmappedFeatures).join("\n").replace(/^/gm, "   ")
       );
     }
   })

scripts/parser-tests/utils/parser-test-runner.js

@@ -121,7 +121,7 @@ class TestRunner {
       count: results.length,
     };
 
-    results.forEach(function(result) {
+    results.forEach(function (result) {
       let classification, isAllowed;
       const inWhitelist = whitelist.has(result.id);
       whitelist.delete(result.id);
@@ -200,7 +200,7 @@ class TestRunner {
         tests: summary.unrecognized,
         label: "non-existent programs specified in the whitelist file",
       },
-    ].forEach(function({ tests, label }) {
+    ].forEach(function ({ tests, label }) {
       if (!tests.length) {
         return;
       }

scripts/rollup-plugin-babel-source.js

@@ -2,7 +2,7 @@ const path = require("path");
 const fs = require("fs");
 const dirname = path.join(__dirname, "..");
 
-module.exports = function() {
+module.exports = function () {
   return {
     name: "babel-source",
     load(id) {

scripts/utils/formatCode.js

@@ -1,11 +1,22 @@
 "use strict";
-const prettier = require("prettier");
 
-module.exports = function formatCode(code, filename) {
-  filename = filename || __filename;
-  const prettierConfig = prettier.resolveConfig.sync(filename);
-  prettierConfig.filepath = filename;
-  prettierConfig.parser = "babel";
+// TODO: Remove this `if` in Babel 8
+// Prettier only supports Node.js 10+, so we can fallback to not formatting
+// o CI on older Node.js versions
 
-  return prettier.format(code, prettierConfig);
-};
+if (process.env.CI && parseInt(process.versions.node, 10) < 10) {
+  module.exports = function formatCode(code) {
+    return code;
+  };
+} else {
+  const prettier = require("prettier");
+
+  module.exports = function formatCode(code, filename) {
+    filename = filename || __filename;
+    const prettierConfig = prettier.resolveConfig.sync(filename);
+    prettierConfig.filepath = filename;
+    prettierConfig.parser = "babel";
+
+    return prettier.format(code, prettierConfig);
+  };
+}