Improve options validation

package.json

@@ -33,6 +33,7 @@
     "execa": "sindresorhus/execa#659f4444795c8c20c5b4ef61c8b9d744136604c0",
     "fancy-log": "^1.3.3",
     "is-ci": "^2.0.0",
+    "jest-validate": "^24.8.0",
     "plugin-error": "^1.0.1",
     "rename-fn": "^1.0.0",
     "through2-concurrent": "^2.0.0"

src/options.js

@@ -1,11 +1,18 @@
+import { validate } from 'jest-validate'
 import isCi from 'is-ci'
 
+import { pickBy } from './utils.js'
+
 // Parse main arguments and options
 // TODO: validate options (including that `input` is a string)
-export const parseOpts = function(opts) {
-  const optsA = { ...DEFAULT_OPTS, ...opts }
-  const optsB = addStdio({ opts: optsA })
-  return optsB
+export const parseOpts = function(opts = {}) {
+  const optsA = pickBy(opts, value => value !== undefined)
+
+  validate(optsA, { exampleConfig: EXAMPLE_OPTS })
+
+  const optsB = { ...DEFAULT_OPTS, ...optsA }
+  const optsC = addStdio({ opts: optsB })
+  return optsC
 }
 
 const DEFAULT_OPTS = {
@@ -14,6 +21,10 @@ const DEFAULT_OPTS = {
   echo: isCi,
 }
 
+const EXAMPLE_OPTS = {
+  ...DEFAULT_OPTS,
+}
+
 // Default to printing shell output to console.
 const addStdio = function({ opts, opts: { stdio } }) {
   // `execa` does not allow mixing `stdio` and `stdout|stderr` options