Add slice support to sequence types.

Fix #4.

news/4.feature.rst

@@ -0,0 +1,3 @@
+Add slicing support to `DataViewSequence`. It is not possible to get, set, or
+delete a slice from it. For `__getitem__`, the return value’s type would match
+the sliced `DataViewSequence`.

src/plette/models/base.py

@@ -90,7 +90,7 @@ def __getitem__(self, key):
         return self.item_class(self._data[key])
 
     def __setitem__(self, key, value):
-        if isinstance(value, self.item_class):
+        if isinstance(value, DataView):
             value = value._data
         self._data[key] = value
 
@@ -133,3 +133,8 @@ def validate(cls, data):
 
     def __iter__(self):
         return (self.item_class(d) for d in self._data)
+
+    def __getitem__(self, key):
+        if isinstance(key, slice):
+            return type(self)(self._data[key])
+        return super(DataViewSequence, self).__getitem__(key)

tests/test_models.py

@@ -127,3 +127,73 @@ def test_meta():
         ],
     })
     assert m.hash.name == "sha256"
+
+
+@pytest.fixture()
+def sources():
+    return models.SourceCollection([
+        {
+            "name": "pypi",
+            "url": "https://pypi.org/simple",
+            "verify_ssl": True,
+        },
+        {
+            "name": "devpi",
+            "url": "http://127.0.0.1:$DEVPI_PORT/simple",
+            "verify_ssl": True,
+        },
+    ])
+
+
+def test_get_slice(sources):
+    sliced = sources[:1]
+    assert isinstance(sliced, models.SourceCollection)
+    assert len(sliced) == 1
+    assert sliced[0] == models.Source({
+        "name": "pypi",
+        "url": "https://pypi.org/simple",
+        "verify_ssl": True,
+    })
+
+
+def test_set_slice(sources):
+    sources[1:] = [
+        {
+            "name": "localpi-4433",
+            "url": "https://127.0.0.1:4433/simple",
+            "verify_ssl": False,
+        },
+        {
+            "name": "localpi-8000",
+            "url": "http://127.0.0.1:8000/simple",
+            "verify_ssl": True,
+        },
+    ]
+    assert sources._data == [
+        {
+            "name": "pypi",
+            "url": "https://pypi.org/simple",
+            "verify_ssl": True,
+        },
+        {
+            "name": "localpi-4433",
+            "url": "https://127.0.0.1:4433/simple",
+            "verify_ssl": False,
+        },
+        {
+            "name": "localpi-8000",
+            "url": "http://127.0.0.1:8000/simple",
+            "verify_ssl": True,
+        },
+    ]
+
+
+def test_del_slice(sources):
+    del sources[:1]
+    assert sources._data == [
+        {
+            "name": "devpi",
+            "url": "http://127.0.0.1:$DEVPI_PORT/simple",
+            "verify_ssl": True,
+        },
+    ]