feat(api): make `getFileInfo()` really async (#4640)

src/cli/util.js

@@ -330,7 +330,7 @@ function formatStdin(context) {
 
 function createIgnorerFromContextOrDie(context) {
   try {
-    return createIgnorer(
+    return createIgnorer.sync(
       context.argv["ignore-path"],
       context.argv["with-node-modules"]
     );

src/common/create-ignorer.js

@@ -1,26 +1,37 @@
 "use strict";
 
 const ignore = require("ignore");
-const fs = require("fs");
 const path = require("path");
+const getFileContentOrNull = require("../utils/get-file-content-or-null");
 
+/**
+ * @param {undefined | string} ignorePath
+ * @param {undefined | boolean} withNodeModules
+ */
 function createIgnorer(ignorePath, withNodeModules) {
-  let ignoreText = "";
+  return (!ignorePath
+    ? Promise.resolve(null)
+    : getFileContentOrNull(path.resolve(ignorePath))
+  ).then(ignoreContent => _createIgnorer(ignoreContent, withNodeModules));
+}
 
-  if (ignorePath) {
-    const resolvedIgnorePath = path.resolve(ignorePath);
-    try {
-      ignoreText = fs.readFileSync(resolvedIgnorePath, "utf8");
-    } catch (readError) {
-      if (readError.code !== "ENOENT") {
-        throw new Error(
-          `Unable to read ${resolvedIgnorePath}: ${readError.message}`
-        );
-      }
-    }
-  }
+/**
+ * @param {undefined | string} ignorePath
+ * @param {undefined | boolean} withNodeModules
+ */
+createIgnorer.sync = function(ignorePath, withNodeModules) {
+  const ignoreContent = !ignorePath
+    ? null
+    : getFileContentOrNull.sync(path.resolve(ignorePath));
+  return _createIgnorer(ignoreContent, withNodeModules);
+};
 
-  const ignorer = ignore().add(ignoreText);
+/**
+ * @param {null | string} ignoreContent
+ * @param {undefined | boolean} withNodeModules
+ */
+function _createIgnorer(ignoreContent, withNodeModules) {
+  const ignorer = ignore().add(ignoreContent || "");
   if (!withNodeModules) {
     ignorer.add("node_modules");
   }

src/common/get-file-info.js

@@ -3,20 +3,39 @@
 const createIgnorer = require("./create-ignorer");
 const options = require("../main/options");
 
+/**
+ * @typedef {{ ignorePath?: string, withNodeModules?: boolean, plugins: object }} FileInfoOptions
+ * @typedef {{ ignored: boolean, inferredParser: string | null }} FileInfoResult
+ */
+
 /**
  * @param {string} filePath
- * @param {{ ignorePath?: string, withNodeModules?: boolean, plugins: object }} opts
+ * @param {FileInfoOptions} opts
+ * @returns {Promise<FileInfoResult>}
  *
  * Please note that prettier.getFileInfo() expects opts.plugins to be an array of paths,
  * not an object. A transformation from this array to an object is automatically done
  * internally by the method wrapper. See withPlugins() in index.js.
  */
-function _getFileInfo(filePath, opts) {
-  let ignored = false;
-  const ignorer = createIgnorer(opts.ignorePath, opts.withNodeModules);
-  ignored = ignorer.ignores(filePath);
+function getFileInfo(filePath, opts) {
+  return createIgnorer(opts.ignorePath, opts.withNodeModules).then(ignorer =>
+    _getFileInfo(ignorer, filePath, opts.plugins)
+  );
+}
 
-  const inferredParser = options.inferParser(filePath, opts.plugins) || null;
+/**
+ * @param {string} filePath
+ * @param {FileInfoOptions} opts
+ * @returns {FileInfoResult}
+ */
+getFileInfo.sync = function(filePath, opts) {
+  const ignorer = createIgnorer.sync(opts.ignorePath, opts.withNodeModules);
+  return _getFileInfo(ignorer, filePath, opts.plugins);
+};
+
+function _getFileInfo(ignorer, filePath, plugins) {
+  const ignored = ignorer.ignores(filePath);
+  const inferredParser = options.inferParser(filePath, plugins) || null;
 
   return {
     ignored,
@@ -24,11 +43,4 @@ function _getFileInfo(filePath, opts) {
   };
 }
 
-// the method has been implemented as asynchronous to avoid possible breaking changes in future
-function getFileInfo(filePath, opts) {
-  return Promise.resolve().then(() => _getFileInfo(filePath, opts));
-}
-
-getFileInfo.sync = _getFileInfo;
-
 module.exports = getFileInfo;

src/utils/get-file-content-or-null.js

@@ -0,0 +1,40 @@
+"use strict";
+
+const fs = require("fs");
+
+/**
+ * @param {string} filename
+ * @returns {Promise<null | string>}
+ */
+function getFileContentOrNull(filename) {
+  return new Promise((resolve, reject) => {
+    fs.readFile(filename, "utf8", (error, data) => {
+      if (error && error.code !== "ENOENT") {
+        reject(createError(filename, error));
+      } else {
+        resolve(error ? null : data);
+      }
+    });
+  });
+}
+
+/**
+ * @param {string} filename
+ * @returns {null | string}
+ */
+getFileContentOrNull.sync = function(filename) {
+  try {
+    return fs.readFileSync(filename, "utf8");
+  } catch (error) {
+    if (error && error.code === "ENOENT") {
+      return null;
+    }
+    throw createError(filename, error);
+  }
+};
+
+function createError(filename, error) {
+  return new Error(`Unable to read ${filename}: ${error.message}`);
+}
+
+module.exports = getFileContentOrNull;