cli: error when input file is unreadable

Close #13

Author: MoOx

bin/cssnext

@@ -17,6 +17,11 @@ program.parse(process.argv)
 
 var input = program.args[0] ? path.resolve(program.args[0]) : null
 var output = program.args[1] ? path.resolve(program.args[1]) : null
+if (input && !fs.existsSync(input)) {
+  console.error(colors.red("Unable to read file"), input)
+  process.exit(1)
+}
+
 function transform() {
   require("read-file-stdin")(input, function(err, buffer) {
     if (err) {

test/index.js

@@ -99,6 +99,12 @@ test("cli", function(t) {
   })
   planned+=1
 
+  exec("bin/cssnext test/cli/wtf.css", function(err, stdout, stderr) {
+    t.ok(err && err.code === 1, "should return an error when input file is unreadable")
+    t.ok(contains(stderr, "Unable to read file"), "should show that the input file is not found")
+  })
+  planned+=2
+
   exec("bin/cssnext test/cli/error.css", function(err, stdout, stderr) {
     t.ok(err && err.code === 2, "should throw an error")
     t.ok(contains(stderr, "encounters an error"), "should output a readable error")