disallow input as sparse matrix in affinity propagation function, Aff… (scikit-learn#13828)

Author: zhaofeng-shu33

sklearn/cluster/affinity_propagation_.py

@@ -364,7 +364,11 @@ def fit(self, X, y=None):
         y : Ignored
 
         """
-        X = check_array(X, accept_sparse='csr')
+        if self.affinity == "precomputed":
+            accept_sparse = False
+        else:
+            accept_sparse = 'csr'
+        X = check_array(X, accept_sparse=accept_sparse)
         if self.affinity == "precomputed":
             self.affinity_matrix_ = X
         elif self.affinity == "euclidean":

sklearn/cluster/tests/test_affinity_propagation.py

@@ -63,7 +63,8 @@ def test_affinity_propagation():
     assert_raises(ValueError, affinity_propagation, S, damping=0)
     af = AffinityPropagation(affinity="unknown")
     assert_raises(ValueError, af.fit, X)
-
+    af_2 = AffinityPropagation(affinity='precomputed')
+    assert_raises(TypeError, af_2.fit, csr_matrix((3, 3)))
 
 def test_affinity_propagation_predict():
     # Test AffinityPropagation.predict