fix: remove extraneous devDependencies on package merge

/cc @pitaj

src/cli/package-install.js

@@ -38,11 +38,12 @@ pkgInstall.updatePackageFile = () => {
 		}
 	});
 
+	const { devDependencies } = defaultPackageContents;
+
 	// Sort dependencies alphabetically
 	dependencies = sortDependencies({ ...dependencies, ...defaultPackageContents.dependencies });
 
-	const packageContents = { ..._.merge(oldPackageContents, defaultPackageContents), dependencies };
-
+	const packageContents = { ..._.merge(oldPackageContents, defaultPackageContents), dependencies, devDependencies };
 	fs.writeFileSync(paths.currentPackage, JSON.stringify(packageContents, null, 2));
 };
 

test/package-install.js

@@ -86,6 +86,15 @@ describe('Package install lib', () => {
 			assert.strictEqual(updated.scripts.preinstall, 'echo "What are you?";');
 		});
 
+		it('should remove extraneous devDependencies', async () => {
+			current.devDependencies.expect = '27.5.1';
+			await fs.writeFile(packageFilePath, JSON.stringify(current, null, 4));
+
+			pkgInstall.updatePackageFile();
+			const updated = JSON.parse(await fs.readFile(packageFilePath, 'utf8'));
+			assert.strictEqual(updated.devDependencies.hasOwnProperty('expect'), false);
+		});
+
 		after(async () => {
 			// Clean up
 			await fs.rename(path.resolve(__dirname, '../install/package.json.bak'), sourcePackagePath);