Update: add question to confirm downgrade (fixes #8870)

lib/config/config-initializer.js

@@ -12,10 +12,12 @@
 const util = require("util"),
     inquirer = require("inquirer"),
     ProgressBar = require("progress"),
+    semver = require("semver"),
     autoconfig = require("./autoconfig.js"),
     ConfigFile = require("./config-file"),
     ConfigOps = require("./config-ops"),
     getSourceCodeOfFiles = require("../util/source-code-util").getSourceCodeOfFiles,
+    ModuleResolver = require("../util/module-resolver"),
     npmUtil = require("../util/npm-util"),
     recConfig = require("../../conf/eslint-recommended"),
     log = require("../logging");
@@ -56,12 +58,35 @@ function writeFile(config, format) {
     }
 }
 
+/**
+ * Get the peer dependencies of the given module.
+ * This adds the gotten value to cache at the first time, then reuses it.
+ * In a process, this function is called twice, but `npmUtil.fetchPeerDependencies` needs to access network which is relatively slow.
+ * @param {string} moduleName The module name to get.
+ * @returns {Object} The peer dependencies of the given module.
+ * This object is the object of `peerDependencies` field of `package.json`.
+ */
+function getPeerDependencies(moduleName) {
+    let result = getPeerDependencies.cache.get(moduleName);
+
+    if (!result) {
+        log.info(`Checking peerDependencies of ${moduleName}`);
+
+        result = npmUtil.fetchPeerDependencies(moduleName);
+        getPeerDependencies.cache.set(moduleName, result);
+    }
+
+    return result;
+}
+getPeerDependencies.cache = new Map();
+
 /**
  * Synchronously install necessary plugins, configs, parsers, etc. based on the config
  * @param   {Object} config  config object
+ * @param   {boolean} [installESLint=true]  If `false` is given, it does not install eslint.
  * @returns {void}
  */
-function installModules(config) {
+function installModules(config, installESLint) {
     const modules = {};
 
     // Create a list of modules which should be installed based on config
@@ -73,11 +98,10 @@ function installModules(config) {
     if (config.extends && config.extends.indexOf("eslint:") === -1) {
         const moduleName = `eslint-config-${config.extends}`;
 
-        log.info(`Checking peerDependencies of ${moduleName}`);
         modules[moduleName] = "latest";
         Object.assign(
             modules,
-            npmUtil.fetchPeerDependencies(`${moduleName}@latest`)
+            getPeerDependencies(`${moduleName}@latest`)
         );
     }
 
@@ -86,15 +110,17 @@ function installModules(config) {
         return;
     }
 
-    // Add eslint to list in case user does not have it installed locally
-    modules.eslint = modules.eslint || "latest";
-
-    // Mark to show messages if it's new installation of eslint.
-    const installStatus = npmUtil.checkDevDeps(["eslint"]);
+    if (installESLint === false) {
+        delete modules.eslint;
+    } else {
+        const installStatus = npmUtil.checkDevDeps(["eslint"]);
 
-    if (installStatus.eslint === false) {
-        log.info("Local ESLint installation not found.");
-        config.installedESLint = true;
+        // Mark to show messages if it's new installation of eslint.
+        if (installStatus.eslint === false) {
+            log.info("Local ESLint installation not found.");
+            modules.eslint = modules.eslint || "latest";
+            config.installedESLint = true;
+        }
     }
 
     // Install packages
@@ -265,9 +291,10 @@ function processAnswers(answers) {
 /**
  * process user's style guide of choice and return an appropriate config object.
  * @param {string} guide name of the chosen style guide
+ * @param {boolean} [installESLint=true]  If `false` is given, it does not install eslint.
  * @returns {Object} config object
  */
-function getConfigForStyleGuide(guide) {
+function getConfigForStyleGuide(guide, installESLint) {
     const guides = {
         google: { extends: "google" },
         airbnb: { extends: "airbnb" },
@@ -279,11 +306,74 @@ function getConfigForStyleGuide(guide) {
         throw new Error("You referenced an unsupported guide.");
     }
 
-    installModules(guides[guide]);
+    installModules(guides[guide], installESLint);
 
     return guides[guide];
 }
 
+/**
+ * Get the version of the local ESLint.
+ * @returns {string|null} The version. If the local ESLint was not found, returns null.
+ */
+function getLocalESLintVersion() {
+    try {
+        const resolver = new ModuleResolver();
+        const eslintPath = resolver.resolve("eslint", process.cwd());
+        const eslint = require(eslintPath);
+
+        return eslint.linter.version || null;
+    } catch (_err) {
+        return null;
+    }
+}
+
+/**
+ * Get the shareable config name of the chosen style guide.
+ * @param {Object} answers The answers object.
+ * @returns {string} The shareable config name.
+ */
+function getStyleGuideName(answers) {
+    if (answers.styleguide === "airbnb" && !answers.airbnbReact) {
+        return "airbnb-base";
+    }
+    return answers.styleguide;
+}
+
+/**
+ * Check whether the local ESLint version conflicts with the required version of the chosen shareable config.
+ * @param {Object} answers The answers object.
+ * @returns {boolean} `true` if the local ESLint is found then it conflicts with the required version of the chosen shareable config.
+ */
+function hasESLintVersionConflict(answers) {
+
+    // Get the local ESLint version.
+    const localESLintVersion = getLocalESLintVersion();
+
+    if (!localESLintVersion) {
+        return false;
+    }
+
+    // Get the required range of ESLint version.
+    const configName = getStyleGuideName(answers);
+    const moduleName = `eslint-config-${configName}@latest`;
+    const requiredESLintVersionRange = getPeerDependencies(moduleName).eslint;
+
+    if (!requiredESLintVersionRange) {
+        return false;
+    }
+
+    answers.localESLintVersion = localESLintVersion;
+    answers.requiredESLintVersionRange = requiredESLintVersionRange;
+
+    // Check the version.
+    if (semver.satisfies(localESLintVersion, requiredESLintVersionRange)) {
+        answers.installESLint = false;
+        return false;
+    }
+
+    return true;
+}
+
 /* istanbul ignore next: no need to test inquirer*/
 /**
  * Ask use a few questions on command prompt
@@ -346,6 +436,21 @@ function promptUser() {
             when(answers) {
                 return ((answers.source === "guide" && answers.packageJsonExists) || answers.source === "auto");
             }
+        },
+        {
+            type: "confirm",
+            name: "installESLint",
+            message(answers) {
+                const verb = semver.ltr(answers.localESLintVersion, answers.requiredESLintVersionRange)
+                    ? "upgrade"
+                    : "downgrade";
+
+                return `The style guide "${answers.styleguide}" requires eslint@${answers.requiredESLintVersionRange}. You are currently using eslint@${answers.localESLintVersion}.\n  Do you want to ${verb}?`;
+            },
+            default: true,
+            when(answers) {
+                return answers.source === "guide" && answers.packageJsonExists && hasESLintVersionConflict(answers);
+            }
         }
     ]).then(earlyAnswers => {
 
@@ -355,11 +460,14 @@ function promptUser() {
                 log.info("A package.json is necessary to install plugins such as style guides. Run `npm init` to create a package.json file and try again.");
                 return void 0;
             }
+            if (earlyAnswers.installESLint === false && !semver.satisfies(earlyAnswers.localESLintVersion, earlyAnswers.requiredESLintVersionRange)) {
+                log.info(`Note: it might not work since ESLint's version is mismatched with the ${earlyAnswers.styleguide} config.`);
+            }
             if (earlyAnswers.styleguide === "airbnb" && !earlyAnswers.airbnbReact) {
                 earlyAnswers.styleguide = "airbnb-base";
             }
 
-            config = getConfigForStyleGuide(earlyAnswers.styleguide);
+            config = getConfigForStyleGuide(earlyAnswers.styleguide, earlyAnswers.installESLint);
             writeFile(config, earlyAnswers.format);
 
             return void 0;
@@ -479,6 +587,7 @@ function promptUser() {
 
 const init = {
     getConfigForStyleGuide,
+    hasESLintVersionConflict,
     processAnswers,
     /* istanbul ignore next */initializeConfig() {
         return promptUser();

lib/util/npm-util.js

@@ -59,7 +59,7 @@ function installSyncSaveDev(packages) {
 /**
  * Fetch `peerDependencies` of the given package by `npm show` command.
  * @param {string} packageName The package name to fetch peerDependencies.
- * @returns {string[]} Gotten peerDependencies.
+ * @returns {Object} Gotten peerDependencies.
  */
 function fetchPeerDependencies(packageName) {
     const fetchedText = childProcess.execSync(

package.json

@@ -65,6 +65,7 @@
     "pluralize": "^4.0.0",
     "progress": "^2.0.0",
     "require-uncached": "^1.0.3",
+    "semver": "^5.3.0",
     "strip-json-comments": "~2.0.1",
     "table": "^4.0.1",
     "text-table": "~0.2.0"
@@ -102,7 +103,6 @@
     "npm-license": "^0.3.3",
     "phantomjs-prebuilt": "^2.1.14",
     "proxyquire": "^1.8.0",
-    "semver": "^5.3.0",
     "shelljs": "^0.7.7",
     "shelljs-nodecli": "~0.1.1",
     "sinon": "^2.3.2",

tests/lib/config/config-initializer.js

@@ -33,14 +33,30 @@ describe("configInitializer", () => {
         npmCheckStub,
         npmInstallStub,
         npmFetchPeerDependenciesStub,
-        init;
+        init,
+        localESLintVersion = null;
 
     const log = {
         info: sinon.spy(),
         error: sinon.spy()
     };
     const requireStubs = {
-        "../logging": log
+        "../logging": log,
+        "../util/module-resolver": class ModuleResolver {
+
+            /**
+             * @returns {string} The path to local eslint to test.
+             */
+            resolve() { // eslint-disable-line class-methods-use-this
+                if (localESLintVersion) {
+                    return `local-eslint-${localESLintVersion}`;
+                }
+                throw new Error("Cannot find module");
+            }
+        },
+        "local-eslint-3.18.0": { linter: { version: "3.18.0" }, "@noCallThru": true },
+        "local-eslint-3.19.0": { linter: { version: "3.19.0" }, "@noCallThru": true },
+        "local-eslint-4.0.0": { linter: { version: "4.0.0" }, "@noCallThru": true }
     };
 
     /**
@@ -245,6 +261,56 @@ describe("configInitializer", () => {
                     ]
                 );
             });
+
+            describe("hasESLintVersionConflict (Note: peerDependencies always `eslint: \"^3.19.0\"` by stubs)", () => {
+                describe("if local ESLint is not found,", () => {
+                    before(() => {
+                        localESLintVersion = null;
+                    });
+
+                    it("should return false.", () => {
+                        const result = init.hasESLintVersionConflict({ styleguide: "airbnb" });
+
+                        assert.equal(result, false);
+                    });
+                });
+
+                describe("if local ESLint is 3.19.0,", () => {
+                    before(() => {
+                        localESLintVersion = "3.19.0";
+                    });
+
+                    it("should return false.", () => {
+                        const result = init.hasESLintVersionConflict({ styleguide: "airbnb" });
+
+                        assert.equal(result, false);
+                    });
+                });
+
+                describe("if local ESLint is 4.0.0,", () => {
+                    before(() => {
+                        localESLintVersion = "4.0.0";
+                    });
+
+                    it("should return true.", () => {
+                        const result = init.hasESLintVersionConflict({ styleguide: "airbnb" });
+
+                        assert.equal(result, true);
+                    });
+                });
+
+                describe("if local ESLint is 3.18.0,", () => {
+                    before(() => {
+                        localESLintVersion = "3.18.0";
+                    });
+
+                    it("should return true.", () => {
+                        const result = init.hasESLintVersionConflict({ styleguide: "airbnb" });
+
+                        assert.equal(result, true);
+                    });
+                });
+            });
         });
 
         describe("auto", () => {