From 2b23e6ffe52b689ccf7d817d4b63370e3136e8aa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=20Erik=20St=C3=B8wer?= <tomerik@getkahoot.com>
Date: Mon, 16 Oct 2017 19:11:09 +0200
Subject: [PATCH] Update: Resolve npm installed formatters (#5900)

---
 docs/user-guide/command-line-interface.md     | 11 ++++++
 lib/cli-engine.js                             | 23 ++++++++++--
 .../eslint-formatter-foo/index.js             |  1 +
 .../cli-engine/eslint-formatter-bar/index.js  |  1 +
 tests/lib/cli-engine.js                       | 36 +++++++++++++++++++
 5 files changed, 69 insertions(+), 3 deletions(-)
 create mode 100644 tests/fixtures/cli-engine/@somenamespace/eslint-formatter-foo/index.js
 create mode 100644 tests/fixtures/cli-engine/eslint-formatter-bar/index.js

diff --git a/docs/user-guide/command-line-interface.md b/docs/user-guide/command-line-interface.md
index 3a7e17650c1e..631a7203b91a 100644
--- a/docs/user-guide/command-line-interface.md
+++ b/docs/user-guide/command-line-interface.md
@@ -333,6 +333,17 @@ Example:
 
     eslint -f ./customformat.js file.js
 
+An npm-installed formatter is resolved with or without `eslint-formatter-` prefix.
+
+Example:
+
+    npm install eslint-formatter-pretty
+
+    eslint -f pretty file.js
+
+    // equivalent:
+    eslint -f eslint-formatter-pretty file.js
+
 When specified, the given format is output to the console. If you'd like to save that output into a file, you can do so on the command line like so:
 
     eslint -f compact file.js > results.txt
diff --git a/lib/cli-engine.js b/lib/cli-engine.js
index 38c49cb31d84..0d94945ee49e 100644
--- a/lib/cli-engine.js
+++ b/lib/cli-engine.js
@@ -26,10 +26,14 @@ const fs = require("fs"),
     validator = require("./config/config-validator"),
     stringify = require("json-stable-stringify"),
     hash = require("./util/hash"),
+    ModuleResolver = require("./util/module-resolver"),
+    Plugins = require("./config/plugins"),
     pkg = require("../package.json");
 
 const debug = require("debug")("eslint:cli-engine");
 
+const resolver = new ModuleResolver();
+
 //------------------------------------------------------------------------------
 // Typedefs
 //------------------------------------------------------------------------------
@@ -670,15 +674,28 @@ class CLIEngine {
             // replace \ with / for Windows compatibility
             format = format.replace(/\\/g, "/");
 
+            let cwd = this.options ? this.options.cwd : process.cwd();
+
+            const namespace = Plugins.getNamespace(format);
+
+            if (namespace) {
+                cwd = `${cwd}/${namespace}`;
+                format = Plugins.removeNamespace(format);
+            }
+
             let formatterPath;
 
             // if there's a slash, then it's a file
             if (format.indexOf("/") > -1) {
-                const cwd = this.options ? this.options.cwd : process.cwd();
-
                 formatterPath = path.resolve(cwd, format);
             } else {
-                formatterPath = `./formatters/${format}`;
+                const npmFormat = /^eslint-formatter-/.test(format) ? format : `eslint-formatter-${format}`;
+
+                try {
+                    formatterPath = resolver.resolve(npmFormat, cwd);
+                } catch (_) {
+                    formatterPath = `./formatters/${format}`;
+                }
             }
 
             try {
diff --git a/tests/fixtures/cli-engine/@somenamespace/eslint-formatter-foo/index.js b/tests/fixtures/cli-engine/@somenamespace/eslint-formatter-foo/index.js
new file mode 100644
index 000000000000..0a55f349ae71
--- /dev/null
+++ b/tests/fixtures/cli-engine/@somenamespace/eslint-formatter-foo/index.js
@@ -0,0 +1 @@
+module.exports = function() {};
diff --git a/tests/fixtures/cli-engine/eslint-formatter-bar/index.js b/tests/fixtures/cli-engine/eslint-formatter-bar/index.js
new file mode 100644
index 000000000000..0a55f349ae71
--- /dev/null
+++ b/tests/fixtures/cli-engine/eslint-formatter-bar/index.js
@@ -0,0 +1 @@
+module.exports = function() {};
diff --git a/tests/lib/cli-engine.js b/tests/lib/cli-engine.js
index 5026d4b197e7..7b17b25d16db 100644
--- a/tests/lib/cli-engine.js
+++ b/tests/lib/cli-engine.js
@@ -2685,6 +2685,42 @@ describe("CLIEngine", () => {
             assert.isFunction(formatter);
         });
 
+        it("should return a function when a formatter prefixed with eslint-formatter is requested", () => {
+            const engine = new CLIEngine({
+                    cwd: getFixturePath("cli-engine")
+                }),
+                formatter = engine.getFormatter("bar");
+
+            assert.isFunction(formatter);
+        });
+
+        it("should return a function when a formatter is requested, also when the eslint-formatter prefix is included in the format argument", () => {
+            const engine = new CLIEngine({
+                    cwd: getFixturePath("cli-engine")
+                }),
+                formatter = engine.getFormatter("eslint-formatter-bar");
+
+            assert.isFunction(formatter);
+        });
+
+        it("should return a function when a formatter is requested within a scoped npm package", () => {
+            const engine = new CLIEngine({
+                    cwd: getFixturePath("cli-engine")
+                }),
+                formatter = engine.getFormatter("@somenamespace/foo");
+
+            assert.isFunction(formatter);
+        });
+
+        it("should return a function when a formatter is requested within a scoped npm package, also when the eslint-formatter prefix is included in the format argument", () => {
+            const engine = new CLIEngine({
+                    cwd: getFixturePath("cli-engine")
+                }),
+                formatter = engine.getFormatter("@somenamespace/eslint-formatter-foo");
+
+            assert.isFunction(formatter);
+        });
+
         it("should return null when a customer formatter doesn't exist", () => {
             const engine = new CLIEngine(),
                 formatterPath = getFixturePath("formatters", "doesntexist.js");