Merge branch 'read-line' into 'develop'

Fix stream-read-line return

See merge request embeddable-common-lisp/ecl!312

src/c/read.d

@@ -1579,7 +1579,8 @@ do_read_delimited_list(int d, cl_object in, bool proper_list)
   if (!ECL_ANSI_STREAM_P(strm)) {
     value0 = _ecl_funcall2(@'gray::stream-read-line', strm);
     value1 = ecl_nth_value(the_env, 1);
-    if (Null(value0) && !Null(value1)) {
+    if ((Null(value0) || (ECL_STRINGP(value0) && (ecl_length(value0) == 0))) &&
+        !Null(value1)) {
       if (!Null(eof_errorp))
         FEend_of_file(strm);
       value0 = eof_value;

src/clos/streams.lsp

@@ -532,9 +532,7 @@
     (loop
      (let ((ch (stream-read-char stream)))
        (cond ((eq ch :eof)
-              (return (values (if (zerop index)
-                                  nil
-                                  (si::shrink-vector res index))
+              (return (values (si::shrink-vector res index)
                               t)))
              (t
               (when (char= ch #\newline)

src/tests/normal-tests/mixed.lsp

@@ -507,7 +507,57 @@
 ;;; (LOOP (fu) nil (bar)) which is not acceptable. To verify
 ;;; that this is not happening we make sure we are not getting
 ;;; (BLOCK NIL NIL) since this is easier to test for.
-(test mixed.0027.format-no-nil-form
+(test mix.0027.format-no-nil-form
   (is (equal (third (second (macroexpand-1 '(formatter "~
 "))))
       '(block nil))))
+
+;;; Created: 2023-12-04 Gray stream proposal is a bit ambiguous about
+;;; the return value of STREAM-READ-LINE. The return from this
+;;; generic function is described as "A string is returned as the
+;;; first value. The second value is true if the string was terminated
+;;; by end-of-file instead of the end of a line." A literal reading of
+;;; this indicates that an EOF with no newline should be returned as
+;;; (VALUES "" T) which is what the default method in the proposal
+;;; does. The following tests ensure that the default Gray method's
+;;; returns are understood by CL:READ-LINE.
+(require :gray-streams)
+
+(defclass character-input-stream
+    (gray:fundamental-character-input-stream)
+  ((value :reader value
+          :initarg :value)
+   (index :accessor index
+          :initform 0)))
+
+(defmethod gray:stream-read-char ((stream character-input-stream))
+  (with-accessors ((value value)
+                   (index index))
+      stream
+    (if (< index (length value))
+        (prog1 (char value index)
+          (incf index))
+        :eof)))
+
+(defmethod gray:stream-unread-char ((stream character-input-stream) character)
+  (with-accessors ((value value)
+                   (index index))
+      stream
+    (when (zerop index)
+      (error "Stream is at beginning, cannot unread character"))
+    (when (char/= character (char value (decf index)))
+      (error "Cannot unread a character that does not match."))
+    nil))
+
+(test mix.0028.read-line-eof
+  (signals end-of-file
+           (read-line (make-instance 'character-input-stream :value ""))))
+
+(test mix.0029.read-line-eof
+  (is (equal (multiple-value-list (read-line (make-instance 'character-input-stream :value "") nil :wibble))
+             '(:wibble t))))
+
+(test mix.0029.read-line-eof
+  (is (equal (multiple-value-list (read-line (make-instance 'character-input-stream :value "a
+")))
+             '("a" nil))))