Check for EOF in DetectReader; for gabriel-vasile#162

Before v1.2.0, DetectReader returned text/plain for empty inputs.
After v1.2.0, it started returning EOF error.
This commit changes DetectReader behavior to how it was before v1.2.0

mimetype.go

@@ -50,7 +50,7 @@ func DetectReader(r io.Reader) (*MIME, error) {
  n := 0
  in = make([]byte, readLimit)
  n, err = io.ReadFull(r, in)
- if err != nil && err != io.ErrUnexpectedEOF {
+ if err != nil && err != io.EOF && err != io.ErrUnexpectedEOF {
  return root, err
  }
  in = in[:n]

mimetype_test.go

@@ -385,6 +385,22 @@ func TestConcurrent(t *testing.T) {
  mimetype.SetLimit(3072)
 }
 
+// For #162.
+func TestEmptyInput(t *testing.T) {
+ mtype, err := mimetype.DetectReader(bytes.NewReader(nil))
+ if err != nil {
+ t.Fatalf("empty reader err; expected: nil, got: %s", err)
+ }
+ plain := "text/plain"
+ if !mtype.Is(plain) {
+ t.Fatalf("empty reader detection; expected: %s, got: %s", plain, mtype)
+ }
+ mtype = mimetype.Detect(nil)
+ if !mtype.Is(plain) {
+ t.Fatalf("empty bytes slice detection; expected: %s, got: %s", plain, mtype)
+ }
+}
+
 // Benchmarking a random slice of bytes is as close as possible to the real
 // world usage. A random byte slice is almost guaranteed to fail being detected.
 //