catch invalid model specification for duplicat

e channels, samples and modifiers.

src/pyhf/mixins.py

@@ -3,6 +3,7 @@
 import logging
 from typing import Any, Sequence
 
+from pyhf import exceptions
 from pyhf.typing import Channel
 
 log = logging.getLogger(__name__)
@@ -21,6 +22,10 @@ class _ChannelSummaryMixin:
     def __init__(self, *args: Any, **kwargs: Sequence[Channel]):
         channels = kwargs.pop('channels')
         super().__init__(*args, **kwargs)
+
+        # check for duplicates
+        self._check_for_duplicates(channels)
+
         self._channels: list[str] = []
         self._samples: list[str] = []
         self._modifiers: list[tuple[str, str]] = []
@@ -89,3 +94,45 @@ def channel_slices(self) -> dict[str, slice]:
         Dictionary mapping channel name to the bin slices in the model.
         """
         return self._channel_slices
+
+    def _check_for_duplicates(self, channels: Sequence[Channel]) -> None:
+        """
+        Check for duplicate channels.
+        Check for duplicate samples within each channel.
+        Check for duplicate modifiers within each sample.
+        """
+        channel_names = [channel['name'] for channel in channels]
+        if len(channel_names) != len(set(channel_names)):
+            duplicates = sorted(
+                set([f"'{x}'" for x in channel_names if channel_names.count(x) > 1])
+            )
+            raise exceptions.InvalidNameReuse(
+                "Duplicate channels "
+                + ", ".join(duplicates)
+                + " found in the model. Rename one of them."
+            )
+        for channel in channels:
+            sample_names = [samples['name'] for samples in channel['samples']]
+            if len(sample_names) != len(set(sample_names)):
+                duplicates = sorted(
+                    set([f"'{x}'" for x in sample_names if sample_names.count(x) > 1])
+                )
+                raise exceptions.InvalidNameReuse(
+                    "Duplicate samples "
+                    + ", ".join(duplicates)
+                    + f" found in the channel '{channel['name']}'. Rename one of them."
+                )
+            for sample in channel['samples']:
+                modifiers = [
+                    (modifier['name'], modifier['type'])
+                    for modifier in sample['modifiers']
+                ]
+                if len(modifiers) != len(set(modifiers)):
+                    duplicates = sorted(
+                        set([f"'{x[0]}'" for x in modifiers if modifiers.count(x) > 1])
+                    )
+                    raise exceptions.InvalidNameReuse(
+                        "Duplicate modifiers "
+                        + ", ".join(duplicates)
+                        + f" of the same type found in channel '{channel['name']}' and sample '{sample['name']}'. Rename one of them."
+                    )

tests/test_schema.py

@@ -714,3 +714,18 @@ def test_schema_tensor_type_disallowed(mocker, backend):
     }
     with pytest.raises(pyhf.exceptions.InvalidSpecification):
         pyhf.schema.validate(spec, "model.json")
+
+
+@pytest.mark.parametrize(
+    'model_file',
+    [
+        'model_duplicate_channels.json',
+        'model_duplicate_samples.json',
+        'model_duplicate_modifiers.json',
+    ],
+)
+def test_schema_catch_duplicates(datadir, model_file):
+    with open(datadir.joinpath(model_file), encoding="utf-8") as spec_file:
+        model_spec = json.load(spec_file)
+    with pytest.raises(pyhf.exceptions.InvalidNameReuse):
+        pyhf.Model(model_spec)

tests/test_schema/model_duplicate_channels.json

@@ -0,0 +1,50 @@
+{
+    "channels": [
+        {
+            "name": "singlechannel",
+            "samples": [
+                {
+                    "name": "signal",
+                    "data": [10],
+                    "modifiers": [
+                        {"name": "mu", "type": "normfactor", "data": null}
+                    ]
+                },
+                {
+                    "name": "background",
+                    "data": [15],
+                    "modifiers": [
+                        {
+                            "name": "uncorr_bkguncrt",
+                            "type": "shapesys",
+                            "data": [5]
+                        }
+                    ]
+                }
+            ]
+        },
+        {
+            "name": "singlechannel",
+            "samples": [
+                {
+                    "name": "signal",
+                    "data": [10],
+                    "modifiers": [
+                        {"name": "mu", "type": "normfactor", "data": null}
+                    ]
+                },
+                {
+                    "name": "background",
+                    "data": [15],
+                    "modifiers": [
+                        {
+                            "name": "uncorr_bkguncrt",
+                            "type": "shapesys",
+                            "data": [5]
+                        }
+                    ]
+                }
+            ]
+        }
+    ]
+}

tests/test_schema/model_duplicate_modifiers.json

@@ -0,0 +1,28 @@
+{
+    "channels": [
+        {
+            "name": "singlechannel",
+            "samples": [
+                {
+                    "name": "signal",
+                    "data": [10],
+                    "modifiers": [
+                        {"name": "mu", "type": "normfactor", "data": null},
+                        {"name": "mu", "type": "normfactor", "data": null}
+                    ]
+                },
+                {
+                    "name": "background",
+                    "data": [15],
+                    "modifiers": [
+                        {
+                            "name": "uncorr_bkguncrt",
+                            "type": "shapesys",
+                            "data": [5]
+                        }
+                    ]
+                }
+            ]
+        }
+    ]
+}

tests/test_schema/model_duplicate_samples.json

@@ -0,0 +1,34 @@
+{
+    "channels": [
+        {
+            "name": "singlechannel",
+            "samples": [
+                {
+                    "name": "signal",
+                    "data": [10],
+                    "modifiers": [
+                        {"name": "mu", "type": "normfactor", "data": null}
+                    ]
+                },
+                {
+                    "name": "signal",
+                    "data": [10],
+                    "modifiers": [
+                        {"name": "mu", "type": "normfactor", "data": null}
+                    ]
+                },
+                {
+                    "name": "background",
+                    "data": [15],
+                    "modifiers": [
+                        {
+                            "name": "uncorr_bkguncrt",
+                            "type": "shapesys",
+                            "data": [5]
+                        }
+                    ]
+                }
+            ]
+        }
+    ]
+}