imapclient: parse fetch attribute "internaldate" as time.Time instead of keeping it as string

similar to the SAVEDATE fetch attribute implemented recently.

Author: mjl-

imapclient/parse.go

@@ -688,7 +688,10 @@ func (c *Conn) xmsgatt1() FetchAttr {
 
 	case "INTERNALDATE":
 		c.xspace()
-		return FetchInternalDate(c.xquoted()) // todo: parsed time
+		s := c.xquoted()
+		v, err := time.Parse("_2-Jan-2006 15:04:05 -0700", s)
+		c.xcheckf(err, "parsing internaldate")
+		return FetchInternalDate{v}
 
 	case "SAVEDATE":
 		c.xspace()

imapclient/protocol.go

@@ -455,7 +455,10 @@ type Address struct {
 }
 
 // "INTERNALDATE" fetch response.
-type FetchInternalDate string            // todo: parsed time
+type FetchInternalDate struct {
+	Date time.Time
+}
+
 func (f FetchInternalDate) Attr() string { return "INTERNALDATE" }
 
 // "SAVEDATE" fetch response. ../rfc/8514:265

imapserver/fetch_test.go

@@ -23,7 +23,7 @@ func TestFetch(t *testing.T) {
 	tc.client.Select("inbox")
 
 	uid1 := imapclient.FetchUID(1)
-	date1 := imapclient.FetchInternalDate("16-Nov-2022 10:01:00 +0100")
+	date1 := imapclient.FetchInternalDate{received}
 	rfcsize1 := imapclient.FetchRFC822Size(len(exampleMsg))
 	env1 := imapclient.FetchEnvelope{
 		Date:      "Mon, 7 Feb 1994 21:52:25 -0800",