feat: Only use "local" modules for formatting

When we resolve configs for prettier and eslint we now use our own version of the respective packages. This way we don't need to check for backwards-compatibility becuase we know the latest compatible version is available, even if the project using prettier-eslint have an older version of prettier installed.

Because of this we can now lower the version requirements of prettier and eslint.

package.json

@@ -17,11 +17,11 @@
   "dependencies": {
     "common-tags": "^1.4.0",
     "dlv": "^1.1.0",
-    "eslint": "^4.5.0",
+    "eslint": "^4.0.0",
     "indent-string": "^3.2.0",
     "lodash.merge": "^4.6.0",
     "loglevel-colored-level-prefix": "^1.0.0",
-    "prettier": "^1.9.0",
+    "prettier": "^1.7.0",
     "pretty-format": "^22.0.3",
     "require-relative": "^0.8.7",
     "typescript": "^2.5.1",

src/__tests__/index.js

@@ -351,24 +351,6 @@ test("calls prettier.resolveConfig.sync with the file path", () => {
   expect(prettierMock.resolveConfig.sync).toHaveBeenCalledWith(filePath);
 });
 
-test("does not raise an error if prettier.resolveConfig.sync is not defined", () => {
-  const filePath = require.resolve("../../tests/fixtures/paths/foo.js");
-  const originalPrettierMockResolveConfigSync = prettierMock.resolveConfig.sync;
-  prettierMock.resolveConfig.sync = undefined;
-
-  function callingFormat() {
-    return format({
-      filePath,
-      text: defaultInputText(),
-      eslintConfig: getESLintConfigWithDefaultRules()
-    });
-  }
-
-  expect(callingFormat).not.toThrowError();
-
-  prettierMock.resolveConfig.sync = originalPrettierMockResolveConfigSync;
-});
-
 test("logs if there is a problem making the CLIEngine", () => {
   const error = new Error("fake error");
   eslintMock.CLIEngine.mockImplementation(() => {

src/index.js

@@ -56,13 +56,13 @@ function format(options) {
   const eslintConfig = merge(
     {},
     options.eslintConfig,
-    getConfig(filePath, eslintPath)
+    getESLintConfig(filePath)
   );
 
   const prettierOptions = merge(
     {},
     filePath && { filepath: filePath },
-    getPrettierConfig(filePath, prettierPath),
+    getPrettierConfig(filePath),
     options.prettierOptions
   );
 
@@ -203,7 +203,7 @@ function getTextFromFilePath(filePath) {
   }
 }
 
-function getConfig(filePath, eslintPath) {
+function getESLintConfig(filePath) {
   const eslintOptions = {};
   if (filePath) {
     eslintOptions.cwd = path.dirname(filePath);
@@ -214,10 +214,10 @@ function getConfig(filePath, eslintPath) {
       "${filePath || process.cwd()}"
     `
   );
-  const configFinder = getESLintCLIEngine(eslintPath, eslintOptions);
+  const cliEngine = getESLintCLIEngine("eslint", eslintOptions);
   try {
     logger.debug(`getting eslint config for file at "${filePath}"`);
-    const config = configFinder.getConfigForFile(filePath);
+    const config = cliEngine.getConfigForFile(filePath);
     logger.trace(
       `eslint config for "${filePath}" received`,
       prettyFormat(config)
@@ -230,14 +230,9 @@ function getConfig(filePath, eslintPath) {
   }
 }
 
-function getPrettierConfig(filePath, prettierPath) {
-  const prettier = requireModule(prettierPath, "prettier");
-
-  // NOTE: Backward-compatibility with old prettier versions (<1.7)
-  //       that don't have ``resolveConfig.sync` method.
-  return typeof prettier.resolveConfig.sync === "undefined"
-    ? {}
-    : prettier.resolveConfig.sync(filePath);
+function getPrettierConfig(filePath) {
+  const prettier = requireModule("prettier", "prettier");
+  return prettier.resolveConfig.sync(filePath);
 }
 
 function requireModule(modulePath, name) {