get-csv: bugfix: return nil on EOF.

* stream.c (get_csv): Let's add a new state init. If get_char
returns nil and we are in the init state, let's bail to a
nil return. While we are at it, let's not allocate the record
or string until we read at least one character. If we read
a character in the init state, let's allocate those two
objects, and then change to the rfield state and fall through
to it to handle the character.

* tests/010/csv.tl: Fix one incorrect test: (tocsv "") now
returns nil, as it should. Add tests for multiple record
extraction, also covering missing line termination on the last
record as well as CR-LF termination.

* txr.1: Documented nil return conditions.

3 files changed, 40 insertions, 5 deletions

diff --git a/stream.c b/stream.c
index 7701ba39..20e5c933 100644
--- a/stream.c
+++ b/stream.c
@@ -5429,9 +5429,8 @@ val get_csv(val source_opt)
                    if3(stringp(source_opt),
                        make_string_input_stream(source_opt),
                        source_opt));
-  val record = vector(zero, nil);
-  val field = mkstring(zero, chr(' '));
-  enum { rfield, qfield, quot } state = rfield;
+  val record = nil, field = nil;
+  enum { init, rfield, qfield, quot } state = init;
   int done = 0;
 
   while (!done) {
@@ -5444,11 +5443,18 @@ val get_csv(val source_opt)
       else if (ch2)
         unget_char(ch2, source);
     } else if (ch == nil) {
+      if (state == init)
+        return nil;
       vec_push(record, field);
       break;
     }
 
     switch (state) {
+    case init:
+      record = vector(zero, nil);
+      field = mkstring(zero, chr(' '));
+      state = rfield;
+      /* fallthrough */
     case rfield:
       switch (c_chr(ch)) {
       case '\n':
diff --git a/tests/010/csv.tl b/tests/010/csv.tl
index 6c93b6c8..d8561c8c 100644
--- a/tests/010/csv.tl
+++ b/tests/010/csv.tl
@@ -13,7 +13,7 @@
                        data expected))))
 
 (mtest-csv
-  "" #("")
+  "" nil
   "," #("" "")
   ",," #("" "" ""))
 
@@ -183,3 +183,25 @@
   #("a\nb" "c#d" "e,f") "#a\nb#,#c##d#,#e,f#\n"
   #("a\n#,b") "#a\n##,b#\n"
   #("a#\n,b\n") "#a##\n,b\n#\n")
+
+(mtest
+  (with-in-string-stream (s "a,b,c\nd,e,f\r\n") (list (get-csv s) (get-csv s) (get-csv s)))
+  (#("a" "b" "c") #("d" "e" "f") nil)
+  (with-in-string-stream (s "a,b,c\nd,e,f\n") (list (get-csv s) (get-csv s) (get-csv s)))
+  (#("a" "b" "c") #("d" "e" "f") nil)
+  (with-in-string-stream (s "a,b,c\nd,e,f") (list (get-csv s) (get-csv s) (get-csv s)))
+  (#("a" "b" "c") #("d" "e" "f") nil)
+  (with-in-string-stream (s "a,b,c\r\n") (list (get-csv s) (get-csv s) (get-csv s)))
+  (#("a" "b" "c") nil nil)
+  (with-in-string-stream (s "a,b,c\n") (list (get-csv s) (get-csv s) (get-csv s)))
+  (#("a" "b" "c") nil nil)
+  (with-in-string-stream (s "a,b,c") (list (get-csv s) (get-csv s) (get-csv s)))
+  (#("a" "b" "c") nil nil)
+  (with-in-string-stream (s "") (list (get-csv s) (get-csv s) (get-csv s)))
+  (nil nil nil)
+  (with-in-string-stream (s "\r") (list (get-csv s) (get-csv s) (get-csv s)))
+  (#("\r") nil nil)
+  (with-in-string-stream (s "\r\n") (list (get-csv s) (get-csv s) (get-csv s)))
+  (#("") nil nil)
+  (with-in-string-stream (s "\n") (list (get-csv s) (get-csv s) (get-csv s)))
+  (#("") nil nil))
diff --git a/txr.1 b/txr.1
index 90beb5bf..68b31ff1 100644
--- a/txr.1
+++ b/txr.1
@@ -85142,7 +85142,14 @@ followed by a comma.
 
 The
 .code get-csv
-function does not recognize or diagnose any errors; it extracts the
+function reads characters from the source stream as if using the
+.code get-char
+function.
+If at least one character from the input source, a record shall be returned.
+If no characters can be read due to end-of-file, it returns
+.codn nil .
+
+The function does not recognize or diagnose any errors; it extracts the
 maximal prefix of the input source which constitutes a valid CSV record.
 Characters not belonging to the CSV record remain in the stream.
 Multiple calls to