hotfix custom interaction class error msg

CHANGELOG.md

@@ -11,6 +11,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Removed
 ### Fixed
 
+## [0.3.3] - 2021-06-11
+### Changed
+- Custom interactions must return three values: a boolean for the interaction,
+  and the indices of residue atoms responsible for the interaction
+### Fixed
+- Custom interactions that only returned a single value instead of three would
+  raise an uninformative error message
+
+
 ## [0.3.2] - 2021-06-11
 ### Added
 - LigNetwork: an interaction diagram with atomistic details for the ligand and

docs/notebooks/how-to.ipynb

@@ -222,9 +222,9 @@
     "\n",
     "This method takes exactly two positional arguments (and as many named arguments as you need): a ligand Residue or Molecule and a protein Residue or Molecule (in this order).\n",
     "\n",
-    "* **Return value(s) for the `detect` method**\n",
+    "* **Return values for the `detect` method**\n",
     "\n",
-    "There are two possibilities here, depending on whether or not you want to access the indices of atoms responsible for the interaction. If you don't need this information, just return `True` if the interaction is detected, `False` otherwise. If you need to access atomic indices, you must return the following items in this order: \n",
+    "You must return the following items in this order: \n",
     "\n",
     "  * `True` or `False` for the detection of the interaction\n",
     "  * The index of the ligand atom, or None if not detected\n",
@@ -239,25 +239,6 @@
    "source": [
     "from scipy.spatial import distance_matrix\n",
     "\n",
-    "# without atom indices\n",
-    "class CloseContact(plf.interactions.Interaction):\n",
-    "    def detect(self, res1, res2, threshold=2.0):\n",
-    "        dist_matrix = distance_matrix(res1.xyz, res2.xyz)\n",
-    "        if (dist_matrix <= threshold).any():\n",
-    "            return True\n",
-    "        return False\n",
-    "\n",
-    "fp = plf.Fingerprint()\n",
-    "fp.closecontact(lmol, pmol[\"ASP129.A\"])"
-   ]
-  },
-  {
-   "cell_type": "code",
-   "execution_count": null,
-   "metadata": {},
-   "outputs": [],
-   "source": [
-    "# with atom indices\n",
     "class CloseContact(plf.interactions.Interaction):\n",
     "    def detect(self, res1, res2, threshold=2.0):\n",
     "        dist_matrix = distance_matrix(res1.xyz, res2.xyz)\n",

prolif/fingerprint.py

@@ -30,7 +30,12 @@
 
 def _return_first_element(f):
     """Modifies the return signature of a function by forcing it to return
-    only the first element if multiple values were returned.
+    only the first element when multiple values are returned
+
+    Raises
+    ------
+    TypeError
+        If the function doesn't return three values
 
     Notes
     -----
@@ -57,10 +62,13 @@ def _return_first_element(f):
     def wrapper(*args, **kwargs):
         results = f(*args, **kwargs)
         try:
-            value, *rest = results
-        except TypeError:
-            value = results
-        return value
+            bool_, lig_idx, prot_idx = results
+        except (TypeError, ValueError):
+            raise TypeError(
+                "Incorrect function signature: the interaction class must "
+                "return 3 values (boolean, int, int)"
+            ) from None
+        return bool_
     return wrapper
 
 
@@ -218,6 +226,7 @@ def bitvector_atoms(self, res1, res2):
             A list containing indices for the protein atoms responsible for
             each interaction
 
+
         .. versionchanged:: 0.3.2
             Atom indices are returned as two separate lists instead of a single
             list of tuples

tests/test_fingerprint.py

@@ -13,23 +13,32 @@
 
 class Dummy(Interaction):
     def detect(self, res1, res2):
-        return 1, 2, 3
+        return True, 4, 2
 
 
-def func_return_single_val():
-    return 0
+def return_value(*args):
+    return args if len(args) > 1 else args[0]
 
 
 def test_wrapper_return():
-    foo = Dummy().detect
-    bar = _return_first_element(foo)
-    assert foo("foo", "bar") == (1, 2, 3)
-    assert bar("foo", "bar") == 1
-    assert bar.__wrapped__("foo", "bar") == (1, 2, 3)
-    baz = _return_first_element(func_return_single_val)
-    assert baz() == 0
-    assert baz.__wrapped__() == 0
-
+    detect = Dummy().detect
+    mod = _return_first_element(detect)
+    assert detect("foo", "bar") == (True, 4, 2)
+    assert mod("foo", "bar") is True
+    assert mod.__wrapped__("foo", "bar") == (True, 4, 2)
+
+
+@pytest.mark.parametrize("returned", [
+    True,
+    (True,),
+    (True, 4)
+])
+def test_wrapper_incorrect_return(returned):
+    mod = _return_first_element(return_value)
+    assert mod.__wrapped__(returned) == returned
+    with pytest.raises(TypeError,
+                       match="Incorrect function signature"):
+        mod(returned)
 
 class TestFingerprint:
     @pytest.fixture
@@ -60,7 +69,7 @@ def test_n_interactions(self, fp):
 
     def test_wrapped(self, fp):
         assert fp.dummy("foo", "bar") == 1
-        assert fp.dummy.__wrapped__("foo", "bar") == (1, 2, 3)
+        assert fp.dummy.__wrapped__("foo", "bar") == (True, 4, 2)
 
     def test_bitvector(self, fp):
         bv = fp.bitvector(ligand_mol, protein_mol["ASP129.A"])