Pull validation helpers out of build_parser() for easier testing.

src/pricehist/cli.py

@@ -69,7 +69,6 @@ def cli(argv=sys.argv, output_file=sys.stdout):
         logging.debug(f"Ended pricehist run at {datetime.now()}.")
 
 
-def build_parser():
 def valid_pair(s):
     base, quote = (s + "/").split("/")[0:2]
     if base == "":
@@ -77,6 +76,7 @@ def build_parser():
         raise argparse.ArgumentTypeError(msg)
     return (base, quote)
 
+
 def valid_date(s):
     if s == "today":
         return today()
@@ -86,18 +86,18 @@ def build_parser():
         msg = f"Not a valid YYYY-MM-DD date: '{s}'."
         raise argparse.ArgumentTypeError(msg)
 
-    def previous_valid_date(s):
+
+def valid_date_before(s):
     return (
         datetime.strptime(valid_date(s), "%Y-%m-%d").date() - timedelta(days=1)
     ).isoformat()
 
-    def following_valid_date(s):
+
+def valid_date_after(s):
     return (
         datetime.strptime(valid_date(s), "%Y-%m-%d").date() + timedelta(days=1)
     ).isoformat()
 
-    def today():
-        return datetime.now().date().isoformat()
 
 def valid_char(s):
     if len(s) == 1:
@@ -106,6 +106,12 @@ def build_parser():
         msg = f"Not a single character: '{s}'."
         raise argparse.ArgumentTypeError(msg)
 
+
+def today():
+    return datetime.now().date().isoformat()
+
+
+def build_parser():
     def formatter(prog):
         return argparse.HelpFormatter(prog, max_help_position=50)
 
@@ -245,7 +251,7 @@ def build_parser():
         "--startx",
         dest="start",
         metavar="DATE",
-        type=following_valid_date,
+        type=valid_date_after,
         help="start date, exclusive",
     )
 
@@ -264,7 +270,7 @@ def build_parser():
         "--endx",
         dest="end",
         metavar="DATE",
-        type=previous_valid_date,
+        type=valid_date_before,
         help="end date, exclusive",
     )