+ checkNpmPluginNameOrThrow(npmName)
+ if (versionArg) checkPluginVersionOrThrow(versionArg)
+
+ const version = versionArg || await getLatestPluginVersion(npmName)
+
+ let toInstall = npmName
+ if (version) toInstall += `@${version}`
+
+ const { stdout } = await execYarn('add ' + toInstall)