From 26a2daab311c8c59942c52f436d380a195db2bd4 Mon Sep 17 00:00:00 2001
From: Victor Hom <vh62@cornell.edu>
Date: Mon, 12 Jun 2017 22:27:24 -0400
Subject: [PATCH] Chore: Cache fs reads in ignored-paths (fixes #8363) (#8706)

---
 lib/ignored-paths.js       | 40 +++++++++++++++++++++++++-------------
 tests/lib/ignored-paths.js | 24 +++++++++++++++++++++++
 2 files changed, 50 insertions(+), 14 deletions(-)

diff --git a/lib/ignored-paths.js b/lib/ignored-paths.js
index 0d9152495ec..d2d89bd9895 100644
--- a/lib/ignored-paths.js
+++ b/lib/ignored-paths.js
@@ -37,7 +37,6 @@ const DEFAULT_OPTIONS = {
     cwd: process.cwd()
 };
 
-
 //------------------------------------------------------------------------------
 // Helpers
 //------------------------------------------------------------------------------
@@ -80,6 +79,7 @@ class IgnoredPaths {
      */
     constructor(options) {
         options = mergeDefaultOptions(options);
+        this.cache = {};
 
         /**
          * add pattern to node-ignore instance
@@ -91,17 +91,6 @@ class IgnoredPaths {
             return ig.addPattern(pattern);
         }
 
-        /**
-         * add ignore file to node-ignore instance
-         * @param {Object} ig, instance of node-ignore
-         * @param {string} filepath, file to add to ig
-         * @returns {array} raw ignore rules
-         */
-        function addIgnoreFile(ig, filepath) {
-            ig.ignoreFiles.push(filepath);
-            return ig.add(fs.readFileSync(filepath, "utf8"));
-        }
-
         this.defaultPatterns = [].concat(DEFAULT_IGNORE_DIRS, options.patterns || []);
         this.baseDir = options.cwd;
 
@@ -155,8 +144,8 @@ class IgnoredPaths {
             if (ignorePath) {
                 debug(`Adding ${ignorePath}`);
                 this.baseDir = path.dirname(path.resolve(options.cwd, ignorePath));
-                addIgnoreFile(this.ig.custom, ignorePath);
-                addIgnoreFile(this.ig.default, ignorePath);
+                this.addIgnoreFile(this.ig.custom, ignorePath);
+                this.addIgnoreFile(this.ig.default, ignorePath);
             }
 
             if (options.ignorePattern) {
@@ -168,6 +157,29 @@ class IgnoredPaths {
         this.options = options;
     }
 
+    /**
+     * read ignore filepath
+     * @param {string} filePath, file to add to ig
+     * @returns {array} raw ignore rules
+     */
+    readIgnoreFile(filePath) {
+        if (typeof this.cache[filePath] === "undefined") {
+            this.cache[filePath] = fs.readFileSync(filePath, "utf8");
+        }
+        return this.cache[filePath];
+    }
+
+    /**
+     * add ignore file to node-ignore instance
+     * @param {Object} ig, instance of node-ignore
+     * @param {string} filePath, file to add to ig
+     * @returns {array} raw ignore rules
+     */
+    addIgnoreFile(ig, filePath) {
+        ig.ignoreFiles.push(filePath);
+        return ig.add(this.readIgnoreFile(filePath));
+    }
+
     /**
      * Determine whether a file path is included in the default or custom ignore patterns
      * @param {string} filepath Path to check
diff --git a/tests/lib/ignored-paths.js b/tests/lib/ignored-paths.js
index 07d96672d0b..1631d37f41c 100644
--- a/tests/lib/ignored-paths.js
+++ b/tests/lib/ignored-paths.js
@@ -164,6 +164,30 @@ describe("IgnoredPaths", () => {
                 )
             );
         });
+
+
+    });
+
+    describe("caching file reads", () => {
+
+        let readFileSyncCount;
+
+        before(() => {
+            readFileSyncCount = sinon.spy(fs, "readFileSync");
+        });
+
+        after(() => {
+            readFileSyncCount.restore();
+        });
+
+        it("should cache readFileSync on same file paths", () => {
+            const ignoreFilePath = getFixturePath(".eslintignore");
+            const ignoredPaths = new IgnoredPaths({ ignore: true, cwd: getFixturePath() });
+
+            ignoredPaths.readIgnoreFile(ignoreFilePath);
+            assert.isTrue(ignoredPaths.contains(ignoreFilePath));
+            sinon.assert.calledOnce(readFileSyncCount);
+        });
     });
 
     describe("initialization with ignorePattern", () => {