Fix: Handle error when running init without npm

lib/config/config-initializer.js

@@ -65,6 +65,7 @@ function writeFile(config, format) {
  * @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`.
+ * Returns null if npm was not found.
  */
 function getPeerDependencies(moduleName) {
     let result = getPeerDependencies.cache.get(moduleName);
@@ -356,7 +357,8 @@ function hasESLintVersionConflict(answers) {
     // Get the required range of ESLint version.
     const configName = getStyleGuideName(answers);
     const moduleName = `eslint-config-${configName}@latest`;
-    const requiredESLintVersionRange = getPeerDependencies(moduleName).eslint;
+    const peerDependencies = getPeerDependencies(moduleName) || {};
+    const requiredESLintVersionRange = peerDependencies.eslint;
 
     if (!requiredESLintVersionRange) {
         return false;

lib/util/npm-util.js

@@ -53,22 +53,39 @@ function installSyncSaveDev(packages) {
     if (!Array.isArray(packages)) {
         packages = [packages];
     }
-    spawn.sync("npm", ["i", "--save-dev"].concat(packages), { stdio: "inherit" });
+    const npmProcess = spawn.sync("npm", ["i", "--save-dev"].concat(packages),
+        { stdio: "inherit" });
+    const error = npmProcess.error;
+
+    if (error && error.code === "ENOENT") {
+        const pluralS = packages.length > 1 ? "s" : "";
+
+        log.error(`Could not execute npm. Please install the following package${pluralS} with your package manager of choice: ${packages.join(", ")}`);
+    }
 }
 
 /**
  * Fetch `peerDependencies` of the given package by `npm show` command.
  * @param {string} packageName The package name to fetch peerDependencies.
- * @returns {Object} Gotten peerDependencies.
+ * @returns {Object} Gotten peerDependencies. Returns null if npm was not found.
  */
 function fetchPeerDependencies(packageName) {
-    const fetchedText = spawn.sync(
+    const npmProcess = spawn.sync(
         "npm",
         ["show", "--json", packageName, "peerDependencies"],
         { encoding: "utf8" }
-    ).stdout.trim();
+    );
+
+    const error = npmProcess.error;
+
+    if (error && error.code === "ENOENT") {
+        return null;
+    }
+    const fetchedText = npmProcess.stdout.trim();
 
     return JSON.parse(fetchedText || "{}");
+
+
 }
 
 /**

tests/lib/util/npm-util.js

@@ -170,7 +170,7 @@ describe("npmUtil", () => {
 
     describe("installSyncSaveDev()", () => {
         it("should invoke npm to install a single desired package", () => {
-            const stub = sandbox.stub(spawn, "sync");
+            const stub = sandbox.stub(spawn, "sync").returns({ stdout: "" });
 
             npmUtil.installSyncSaveDev("desired-package");
             assert(stub.calledOnce);
@@ -180,14 +180,26 @@ describe("npmUtil", () => {
         });
 
         it("should accept an array of packages to install", () => {
-            const stub = sandbox.stub(spawn, "sync");
+            const stub = sandbox.stub(spawn, "sync").returns({ stdout: "" });
 
             npmUtil.installSyncSaveDev(["first-package", "second-package"]);
             assert(stub.calledOnce);
             assert.equal(stub.firstCall.args[0], "npm");
             assert.deepEqual(stub.firstCall.args[1], ["i", "--save-dev", "first-package", "second-package"]);
             stub.restore();
         });
+
+        it("should log an error message if npm throws ENOENT error", () => {
+            const logErrorStub = sandbox.stub(log, "error");
+            const npmUtilStub = sandbox.stub(spawn, "sync").returns({ error: { code: "ENOENT" } });
+
+            npmUtil.installSyncSaveDev("some-package");
+
+            assert(logErrorStub.calledOnce);
+
+            logErrorStub.restore();
+            npmUtilStub.restore();
+        });
     });
 
     describe("fetchPeerDependencies()", () => {
@@ -200,5 +212,15 @@ describe("npmUtil", () => {
             assert.deepEqual(stub.firstCall.args[1], ["show", "--json", "desired-package", "peerDependencies"]);
             stub.restore();
         });
+
+        it("should return null if npm throws ENOENT error", () => {
+            const stub = sandbox.stub(spawn, "sync").returns({ error: { code: "ENOENT" } });
+
+            const peerDependencies = npmUtil.fetchPeerDependencies("desired-package");
+
+            assert.isNull(peerDependencies);
+
+            stub.restore();
+        });
     });
 });