Fix resp_text to match RFC 3501

Specifically, "text" is allowed to begin with "[" or "=". Disallowing
that was an older RFC2060 restriction.

(RFC 2060 was written in 1996. RFC 3501 in 2003)  :)

Author: nevans

lib/net/imap.rb

@@ -1774,8 +1774,7 @@ def ensure_mod_sequence_value(num)
     # Net::IMAP::ResponseText represents texts of responses.
     # The text may be prefixed by the response code.
     #
-    #   resp_text       ::= ["[" resp_text_code "]" SPACE] (text_mime2 / text)
-    #                       ;; text SHOULD NOT begin with "[" or "="
+    #   resp_text       ::= ["[" resp-text-code "]" SP] text
     #
     # ==== Fields:
     #
@@ -3132,22 +3131,21 @@ def text
         match(T_TEXT, lex_state: EXPR_TEXT).value
       end
 
+      # resp-text       = ["[" resp-text-code "]" SP] text
       def resp_text
-        @lex_state = EXPR_RTEXT
-        token = lookahead
-        if token.symbol == T_LBRA
+        token = match(T_LBRA, T_TEXT, lex_state: EXPR_RTEXT)
+        case token.symbol
+        when T_LBRA
           code = resp_text_code
-        else
-          code = nil
+          match(T_RBRA)
+          accept_space # violating RFC
+          ResponseText.new(code, text)
+        when T_TEXT
+          ResponseText.new(nil, token.value)
         end
-        token = match(T_TEXT)
-        @lex_state = EXPR_BEG
-        return ResponseText.new(code, token.value)
       end
 
       def resp_text_code
-        @lex_state = EXPR_BEG
-        match(T_LBRA)
         token = match(T_ATOM)
         name = token.value.upcase
         case name
@@ -3163,16 +3161,12 @@ def resp_text_code
           token = lookahead
           if token.symbol == T_SPACE
             shift_token
-            @lex_state = EXPR_CTEXT
-            token = match(T_TEXT)
-            @lex_state = EXPR_BEG
+            token = match(T_TEXT, lex_state: EXPR_CTEXT)
             result = ResponseCode.new(name, token.value)
           else
             result = ResponseCode.new(name, nil)
           end
         end
-        match(T_RBRA)
-        @lex_state = EXPR_RTEXT
         return result
       end
 

test/net/imap/test_imap_response_parser.rb

@@ -301,6 +301,14 @@ def test_msg_att_modseq_data
     assert_equal(12345, response.data.attr["MODSEQ"])
   end
 
+  def test_msg_rfc3501_response_text_with_T_LBRA
+    parser = Net::IMAP::ResponseParser.new
+    response = parser.parse("RUBY0004 OK [READ-WRITE] [Gmail]/Sent Mail selected. (Success)\r\n")
+    assert_equal("RUBY0004", response.tag)
+    assert_equal("READ-WRITE", response.data.code.name)
+    assert_equal("[Gmail]/Sent Mail selected. (Success)", response.data.text)
+  end
+
   def test_continuation_request_without_response_text
     parser = Net::IMAP::ResponseParser.new
     response = parser.parse("+\r\n")