From 66c897b63d7ed6e1c78b09b922b5d02b95e5d103 Mon Sep 17 00:00:00 2001
From: Jack Brown <jack@xanadu.ai>
Date: Wed, 11 Oct 2023 12:03:47 -0400
Subject: [PATCH] handle edge cases

---
 pennylane/data/data_manager/foldermap.py  | 23 +++++----
 tests/data/data_manager/test_foldermap.py | 61 +++++++++++++++++++++--
 2 files changed, 70 insertions(+), 14 deletions(-)

diff --git a/pennylane/data/data_manager/foldermap.py b/pennylane/data/data_manager/foldermap.py
index d536130c74a..bf4c0cde4e0 100644
--- a/pennylane/data/data_manager/foldermap.py
+++ b/pennylane/data/data_manager/foldermap.py
@@ -119,6 +119,7 @@ def find(
 
             while curr:
                 curr_description, curr_level = curr.pop()
+
                 if param_arg == ParamArg.FULL:
                     next_params = curr_level
                 elif param_arg == ParamArg.DEFAULT:
@@ -131,29 +132,29 @@ def find(
                 else:
                     next_params = param_arg
 
-                next_ = []
                 for next_param in next_params:
                     try:
                         fmap_next = curr_level[next_param]
                     except KeyError:
                         continue
 
-                    next_.append(
+                    todo.append(
                         (
                             Description((*curr_description.items(), (param_name, next_param))),
                             fmap_next,
                         )
                     )
 
-                if len(next_) == 0:
-                    params_list_fmt = ", ".join(f"'{val}'" for val in next_params)
-                    param_value_slug = f"{param_name} value(s) {params_list_fmt} are not available"
-
-                    raise ValueError(
-                        f"{param_value_slug}. Available values are: {list(curr_level)}"
-                    )
-
-                todo.extend(next_)
+            if len(todo) == 0:
+                # None of the parameters matched
+                param_arg_repr = (
+                    repr([param_arg])
+                    if isinstance(param_arg, (str, ParamArg))
+                    else repr(list(param_arg))
+                )
+                raise ValueError(
+                    f"{param_name} value(s) {param_arg_repr} are not available. Available values are: {list(curr_level)}"
+                )
 
             curr, todo = todo, curr
 
diff --git a/tests/data/data_manager/test_foldermap.py b/tests/data/data_manager/test_foldermap.py
index 9a04b61d76e..5c9e3385e46 100644
--- a/tests/data/data_manager/test_foldermap.py
+++ b/tests/data/data_manager/test_foldermap.py
@@ -19,6 +19,7 @@
 
 from pennylane.data.data_manager import DEFAULT, FULL, DataPath
 from pennylane.data.data_manager.foldermap import Description, FolderMapView
+import re
 
 pytestmark = pytest.mark.data
 
@@ -125,6 +126,38 @@ class TestFolderMapView:
                     ),
                 ],
             ),
+            (
+                {"missing_default": DEFAULT, "molname": "O2", "basis": FULL, "bondlength": ["0.6"]},
+                [
+                    (
+                        {"molname": "O2", "basis": "STO-3G", "bondlength": "0.6"},
+                        "qchem/O2/STO-3G/0.6.h5",
+                    ),
+                ],
+            ),
+            (
+                {
+                    "missing_default": DEFAULT,
+                    "molname": "O2",
+                    "basis": FULL,
+                    "bondlength": ["0.6", "200"],
+                },
+                [
+                    (
+                        {"molname": "O2", "basis": "STO-3G", "bondlength": "0.6"},
+                        "qchem/O2/STO-3G/0.6.h5",
+                    ),
+                ],
+            ),
+            (
+                {"missing_default": FULL, "molname": "O2", "bondlength": ["0.6"]},
+                [
+                    (
+                        {"molname": "O2", "basis": "STO-3G", "bondlength": "0.6"},
+                        "qchem/O2/STO-3G/0.6.h5",
+                    ),
+                ],
+            ),
         ],
     )
     def test_find(self, foldermap, kwds, expect):  # pylint: disable=redefined-outer-name
@@ -155,14 +188,36 @@ def test_find_missing_arg_no_default(self):
         with pytest.raises(ValueError, match="No default available for parameter 'molname'"):
             FolderMapView(FOLDERMAP).find("qchem")
 
-    def test_find_invalid_parameter(self):
+    @pytest.mark.parametrize(
+        "arg, error_fmt", [("Z3", repr(["Z3"])), (("Z3", "Z4"), repr(["Z3", "Z4"]))]
+    )
+    def test_find_invalid_parameter(self, arg, error_fmt):
         """Test that a ValueError is raised when a parameter provided
         does not exist."""
 
         with pytest.raises(
-            ValueError, match=r"molname value\(s\) 'Z3' is not available. Available values are: \['O2', 'H2'\]"
+            ValueError,
+            match=re.escape(
+                f"molname value(s) {error_fmt} are not available. Available values are: ['O2', 'H2']"
+            ),
         ):
-            FolderMapView(FOLDERMAP).find("qchem", molname="Z3")
+            FolderMapView(FOLDERMAP).find("qchem", molname=arg)
+
+    @pytest.mark.parametrize("basis", [FULL, DEFAULT])
+    def test_find_invalid_parameters_after_full_default(self, basis):
+        """Test that a ValueError is raised when a parameter provided
+        does not exist, after a 'full' or 'default' parameter has been provided for a
+        higher-priority parameter."""
+
+        with pytest.raises(
+            ValueError,
+            match=(
+                r"bondlength value\(s\) \['0.20', '200'\] are not available. Available values are: \['0.5', '0.6'\]"
+            ),
+        ):
+            FolderMapView(FOLDERMAP).find(
+                "qchem", molname="O2", basis=basis, bondlength=["0.20", "200"]
+            )
 
     @pytest.mark.parametrize(
         "init, key, expect",