made repeated keys an error

Author: yucongalicechen

src/diffpy/labpdfproc/labpdfprocapp.py

@@ -63,11 +63,10 @@ def get_args():
         "--user-metadata",
         metavar="KEY=VALUE",
         nargs="+",
-        help="Specify (multiple) key-value pairs to be loaded into metadata using the format key=value. "
-        "Please separate each pair with whitespace, and make sure no whitespaces before or after the = sign. "
-        "Avoid using = in keys. If multiple = signs are present, only the first one separates the key and value. "
-        "If you repeat key names, it will replace previous values. "
-        "If a key or value contains whitespace, enclose it in quotes. "
+        help="Specify key-value pairs to be loaded into metadata using the format key=value. "
+        "Separate pairs with whitespace, and ensure no whitespaces before or after the = sign. "
+        "Avoid using = in keys. If multiple = signs are present, only the first separates the key and value. "
+        "Please do not repeat key names. If a key or value contains whitespace, enclose it in quotes. "
         'For example, you can specify -u "facility=NSLS II" beamline=28ID-2 "favorite color"=blue',
     )
     args = p.parse_args()

src/diffpy/labpdfproc/tests/test_tools.py

@@ -85,7 +85,6 @@ def test_set_wavelength_bad(inputs, msg):
         [["facility=NSLS II", "beamline=28ID-2", "favorite color=blue"]],
         [["facility", "NSLS II"], ["beamline", "28ID-2"], ["favorite color", "blue"]],
     ),
-    ([["facility=NSLS II", "facility=NSLS III"]], [["facility", "NSLS III"]]),
     ([["x=y=z"]], [["x", "y=z"]]),
 ]
 
@@ -105,16 +104,33 @@ def test_load_user_metadata(inputs, expected):
 
 
 params6 = [
-    ([["facility=NSLS", "II"]]),
-    ([["favorite", "color=blue"]]),
-    ([["beamline", "=", "28ID-2"]]),
+    (
+        [["facility=NSLS", "II"]],
+        [
+            "Please provide key-value pairs in the format key=value. "
+            "For more information, use `labpdfproc --help.`"
+        ],
+    ),
+    (
+        [["favorite", "color=blue"]],
+        "Please provide key-value pairs in the format key=value. "
+        "For more information, use `labpdfproc --help.`",
+    ),
+    (
+        [["beamline", "=", "28ID-2"]],
+        "Please provide key-value pairs in the format key=value. "
+        "For more information, use `labpdfproc --help.`",
+    ),
+    ([["facility=NSLS II", "facility=NSLS III"]], ["Please do not specify repeated keys: facility. "]),
+    ([["wavelength=2"]], ["Please do not specify repeated keys: wavelength. "]),
 ]
 
 
-@pytest.mark.parametrize("inputs", params6)
-def test_load_user_metadata_bad(inputs):
+@pytest.mark.parametrize("inputs, msg", params6)
+def test_load_user_metadata_bad(inputs, msg):
     actual_parser = ArgumentParser()
+    actual_parser.add_argument("--wavelength")
     actual_parser.add_argument("--user-metadata")
     actual_args = actual_parser.parse_args(["--user-metadata", inputs[0]])
-    with pytest.raises(ValueError):
+    with pytest.raises(ValueError, match=re.escape(msg[0])):
         actual_args = load_user_metadata(actual_args)

src/diffpy/labpdfproc/tools.py

@@ -93,6 +93,8 @@ def load_user_metadata(args):
                     "For more information, use `labpdfproc --help.`"
                 )
             key, value = _load_key_value_pair(item)
+            if hasattr(args, key):
+                raise ValueError(f"Please do not specify repeated keys: {key}. ")
             setattr(args, key, value)
     delattr(args, "user_metadata")
     return args