Added one test, for embedded newlines, and fixed all the bugs it found

lua/csv.lua

@@ -201,7 +201,8 @@ local function separated_values_iterator(file, parameters)
   local function sub(a, b)
     truncate()
     extend(b)
-    return buffer:sub(anchor_pos + a - 1, anchor_pos + b - 1)
+    local b = b == -1 and b or anchor_pos + b - 1
+    return buffer:sub(anchor_pos + a - 1, b)
   end
 
 
@@ -237,8 +238,8 @@ local function separated_values_iterator(file, parameters)
           format(filename, field_start_line, field_start_column))
       end
       tidy = fix_quotes
-      field_end, sep_end, this_sep = find("%s*(%S)", current_pos+1)
-      if not this_sep:match(sep) then
+      field_end, sep_end, this_sep = find(" *([^ ])", current_pos+1)
+      if this_sep and not this_sep:match(sep) then
         error(("%s:%d:%d: unmatched quote"):
           format(filename, field_start_line, field_start_column))
       end
@@ -247,7 +248,7 @@ local function separated_values_iterator(file, parameters)
       tidy = trim_space
     end
 
-    -- Look for the separator or a newline.
+    -- Look for the separator or a newline or the end of the file
     field_end = (field_end or 0) - 1
 
     -- Read the field, then convert all the line endings to \n, and

lua/test.lua

@@ -0,0 +1,39 @@
+pcall(require, "strict")
+local csv = require"csv"
+
+local errors = 0
+
+local function test(filename, correct_result, parameters)
+  local result = {}
+  local f = csv.open(filename)
+  for r in f:lines() do
+    result[#result+1] = table.concat(r, ",")
+  end
+  result = table.concat(result, "\n")
+  if result ~= correct_result then
+    io.stderr:write(
+      ("Error reading %s.  Expected output\n%s\nActual output\n%s\n"):
+      format(filename, correct_result, result))
+    errors = errors + 1
+  end
+end
+
+test("../test-data/embedded-newlines.csv", [[
+embedded
+newline,embedded
+newline,embedded
+newline
+embedded
+newline,embedded
+newline,embedded
+newline]])
+
+if errors == 0 then
+  io.stdout:write("Passed\n")
+elseif errors == 1 then
+  io.stdout:write("1 error\n")
+else
+  io.stdout:write(("%d errors\n"):format(errors))
+end
+
+os.exit(errors)

test-data/embedded-newlines.csv

@@ -0,0 +1,8 @@
+"embedded
+newline","embedded
+newline","embedded
+newline"
+"embedded
+newline","embedded
+newline","embedded
+newline"