Don't do ad-hoc serialization, update exclusions

README.md

 ## Exclusions
 
 The config file formats that Prettier uses are not able to represent all of
-Prettier's default values. For instance, TOML has no concept of `null`, neither
-TOML nor JSON can represent `Infinity`, and no format except actual JavaScript
-can represent `undefined`. As a result, depending on the chosen format, some
-configuration options may be excluded. The current list of exclusions is as
-follows:
+Prettier's default values. For instance, JSON can't represent `undefined` or
+`Infinity`, and no format except actual JavaScript can represent `undefined`.
+As a result, depending on the chosen format, some configuration options may be
+excluded. The current list of exclusions is as follows:
 
 
 | Format | Excluded Options                  |
 |--------|-----------------------------------|
 | JSON   | `rangeEnd` , `filepath`, `parser` |
-| TOML   | `rangeEnd`, `filepath`, `parser`  |
-| YAML   | `filepath`, `parser`  |
+| TOML   | `rangeEnd`                        |
+| YAML   | `filepath`                        |
 
 ## License
 

index.js

 #!/usr/bin/env node
 
 const fs = require('fs');
-const minimist = require('minimist');
 const path = require('path');
+const { inspect } = require('util');
+
+const minimist = require('minimist');
 const prettier = require('prettier');
+const TOML = require('@iarna/toml');
+const YAML = require('yaml');
 
 const defaultConfigFor = function(format) {
   let config = prettier.getSupportInfo().options;
 
-  if (!['js', 'yaml'].includes(format)) {
-    config = config.filter(
-      option => ![null, Infinity].includes(option.default)
-    );
+  if (format.match(/json/)) {
+    config = config.filter(option => option.default !== Infinity);
   }
 
   if (format != 'js') {
   yaml: {
     filename: '.prettierrc.yaml',
     generate: function() {
-      return Object.entries(defaultConfigFor('yaml'))
-        .map(([key, value]) => {
-          if (typeof value === 'string' && value === '') return `${key}: ''`;
-          if (value === null) return `${key}: ~`;
-          if (value === Infinity) return `${key}: .inf`;
-          if (!!value.forEach && value.length === 0) return `${key}: []`;
-          return `${key}: ${value}`;
-        })
-        .join('\n');
+      return YAML.stringify(defaultConfigFor('yaml'));
     },
   },
   toml: {
     filename: '.prettierrc.toml',
     generate: function() {
-      return Object.entries(defaultConfigFor('toml'))
-        .map(([key, value]) => {
-          if (typeof value === 'string') return `${key} = "${value}"`;
-          if (!!value.forEach && value.length === 0) return `${key} = []`;
-          return `${key} = ${value}`;
-        })
-        .join('\n');
+      return TOML.stringify(defaultConfigFor('toml'));
     },
   },
   js: {
     filename: '.prettierrc.js',
     generate: function() {
-      const contents = Object.entries(defaultConfigFor('js'))
-        .map(([key, value]) => {
-          if (typeof value === 'string') return `  ${key}: '${value}',`;
-          if (typeof value === 'undefined') return `  ${key}: undefined,`;
-          if (value === null) return `  ${key}: null,`;
-          if (!!value.forEach && value.length === 0) return `${key}: [],`;
-          return `  ${key}: ${value},`;
-        })
-        .join('\n');
-      return `module.exports = {\n${contents}\n};`;
+      return `module.exports = ${inspect(defaultConfigFor('js'))};`;
     },
   },
   'package.json': {

package-lock.json

       "version": "7.8.4",
       "resolved": "https://registry.npmjs.org/@babel/runtime/-/runtime-7.8.4.tgz",
       "integrity": "sha512-neAp3zt80trRVBI1x0azq6c57aNBqYZH8KhMm3TaB7wEI5Q4A2SHfBHE8w9gOhI/lrqxtEbXZgQIrHP+wvSGwQ==",
-      "dev": true,
       "requires": {
         "regenerator-runtime": "^0.13.2"
       }
     },
+    "@iarna/toml": {
+      "version": "2.2.3",
+      "resolved": "https://registry.npmjs.org/@iarna/toml/-/toml-2.2.3.tgz",
+      "integrity": "sha512-FmuxfCuolpLl0AnQ2NHSzoUKWEJDFl63qXjzdoWBVyFCXzMGm1spBzk7LeHNoVCiWCF7mRVms9e6jEV9+MoPbg=="
+    },
     "balanced-match": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/balanced-match/-/balanced-match-1.0.0.tgz",
     "prettier": {
       "version": "1.19.1",
       "resolved": "https://registry.npmjs.org/prettier/-/prettier-1.19.1.tgz",
-      "integrity": "sha512-s7PoyDv/II1ObgQunCbB9PdLmUcBZcnWOcxDh7O0N/UwDEsHyqkW+Qh28jW+mVuCdx7gLB0BotYI1Y6uI9iyew==",
-      "dev": true
+      "integrity": "sha512-s7PoyDv/II1ObgQunCbB9PdLmUcBZcnWOcxDh7O0N/UwDEsHyqkW+Qh28jW+mVuCdx7gLB0BotYI1Y6uI9iyew=="
     },
     "readable-stream": {
       "version": "1.1.14",
     "regenerator-runtime": {
       "version": "0.13.3",
       "resolved": "https://registry.npmjs.org/regenerator-runtime/-/regenerator-runtime-0.13.3.tgz",
-      "integrity": "sha512-naKIZz2GQ8JWh///G7L3X6LaQUAMp2lvb1rvwwsURe/VXwD6VMfr+/1NuNw3ag8v2kY1aQ/go5SNn79O9JU7yw==",
-      "dev": true
+      "integrity": "sha512-naKIZz2GQ8JWh///G7L3X6LaQUAMp2lvb1rvwwsURe/VXwD6VMfr+/1NuNw3ag8v2kY1aQ/go5SNn79O9JU7yw=="
     },
     "regexp.prototype.flags": {
       "version": "1.3.0",
         "xtend": "~2.1.1"
       }
     },
-    "toml": {
-      "version": "3.0.0",
-      "resolved": "https://registry.npmjs.org/toml/-/toml-3.0.0.tgz",
-      "integrity": "sha512-y/mWCZinnvxjTKYhJ+pYxwD0mRLVvOtdS2Awbgxln6iEnt4rk0yBxeSBHkGJcPucRiG0e55mwWp+g/05rsrd6w==",
-      "dev": true
-    },
     "wrappy": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/wrappy/-/wrappy-1.0.2.tgz",
       "version": "1.7.2",
       "resolved": "https://registry.npmjs.org/yaml/-/yaml-1.7.2.tgz",
       "integrity": "sha512-qXROVp90sb83XtAoqE8bP9RwAkTTZbugRUTm5YeFCBfNRPEp2YzTeqWiz7m5OORHzEvrA/qcGS8hp/E+MMROYw==",
-      "dev": true,
       "requires": {
         "@babel/runtime": "^7.6.3"
       }

package.json

     "index.js"
   ],
   "dependencies": {
+    "@iarna/toml": "^2.2.3",
     "minimist": "^1.2.0",
-    "prettier": "^1.19.1"
+    "prettier": "^1.19.1",
+    "yaml": "^1.7.2"
   },
   "devDependencies": {
     "faucet": "0.0.1",
-    "tape": "^4.13.0",
-    "toml": "^3.0.0",
-    "yaml": "^1.7.2"
+    "tape": "^4.13.0"
   }
 }

test.js

 const fs = require('fs');
 const test = require('tape');
-const TOML = require('toml');
+const TOML = require('@iarna/toml');
 const YAML = require('yaml');
 
 const { defaultConfigFor, formats } = require('.');
   t.equal(YAML.parse(result).rangeEnd, Infinity);
 });
 
-test("YAML doesn't support undefined so leave out filepath and parser", t => {
+test('TOML supports infinity, leave rangeEnd in', t => {
   t.plan(2);
-  const result = formats.yaml.generate();
+  const result = TOML.parse(formats.toml.generate());
+  t.true(Object.keys(result).includes('rangeEnd'));
+  t.equal(result.rangeEnd, Infinity);
+});
+
+test("JSON doesn't support undefined, leave out filepath and parser", t => {
+  t.plan(2);
+  const result = JSON.parse(formats.json.generate());
   t.false(Object.keys(result).includes('parser'));
   t.false(Object.keys(result).includes('filepath'));
 });
 
-test("TOML doesn't support infinity, so leave out rangeEnd", t => {
-  t.plan(1);
-  const result = formats.toml.generate();
-  t.false(Object.keys(result).includes('rangeEnd'));
+test("YAML doesn't support undefined, leave out filepath and parser", t => {
+  t.plan(2);
+  const result = YAML.parse(formats.yaml.generate());
+  t.false(Object.keys(result).includes('parser'));
+  t.false(Object.keys(result).includes('filepath'));
 });
 
-test('JS supports undefined, so leave in parser and filepath', t => {
+test('JS supports undefined, leave in parser and filepath', t => {
   t.plan(4);
   const result = eval(formats.js.generate());
   t.equal(result.parser, undefined);