if there's nothing being piped in, try for a package-lock in cwd

functions/get-input.js

@@ -1,10 +1,37 @@
 import {createReadStream} from "fs"
 import path from "path"
+import fs from "fs"
+import {promisify} from "util"
 
-export default async function getInput ({file = "-"}) {
-	let stream = file == "-"
-		? process.stdin
-		:	createReadStream(path.resolve(file))
+async function checkPathIsRegularFile (path) {
+	return promisify(fs.stat)(path)
+		.then(stats => stats.isFile())
+		.catch(() => false)
+}
+
+async function getStream ({file, isTTY}) {
+	if (file != null && file != "-") {
+		let filepath = path.resolve(file)
+		if (!await checkPathIsRegularFile(filepath)) {
+			throw new Error(`not a file: "${filepath}"`)
+		}
+		return createReadStream(filepath)
+	}
+
+	let packageLockPath = "package-lock.json"
+
+	let packageLockExists = await checkPathIsRegularFile(packageLockPath)
+
+	if (!file && isTTY && packageLockExists) {
+		return createReadStream(packageLockPath)
+	}
+
+	return process.stdin
+}
+
+export default async function getInput ({file}) {
+	let {isTTY} = process.stdin
+	let stream = await getStream({file, isTTY})
 
 	stream.resume()
 	stream.setEncoding("utf-8")