write out todo plan for moving to generic test API

src/Algebra/Graph/NonEmpty/AdjacencyIntMap.hs

@@ -55,15 +55,12 @@ import Prelude hiding (reverse)
 import Control.DeepSeq
 import Data.Coerce
 import Data.List ((\\))
-import Data.List.NonEmpty (NonEmpty (..), nonEmpty, toList, reverse)
-import Data.Maybe
+import Data.List.NonEmpty (NonEmpty (..), toList, reverse, fromList)
 import Data.IntSet (IntSet)
 import Data.Set (Set)
 import Data.Tree
 import GHC.Generics
 
-import Algebra.Graph.Internal
-
 import qualified Algebra.Graph.AdjacencyIntMap as AIM
 import qualified Data.IntSet                   as IntSet
 
@@ -378,7 +375,7 @@ edgeCount = coerce AIM.edgeCount
 -- vertexList1 . 'vertices1' == 'Data.List.NonEmpty.nub' . 'Data.List.NonEmpty.sort'
 -- @
 vertexList1 :: AdjacencyIntMap -> NonEmpty Int
-vertexList1 = unsafeNonEmpty . coerce AIM.vertexList
+vertexList1 = fromList . coerce AIM.vertexList
 
 -- | The sorted list of edges of a graph.
 -- Complexity: /O(n + m)/ time and /O(m)/ memory.

src/Algebra/Graph/NonEmpty/AdjacencyMap.hs

@@ -54,15 +54,12 @@ import Prelude hiding (reverse)
 import Control.DeepSeq
 import Data.Coerce
 import Data.List ((\\))
-import Data.List.NonEmpty (NonEmpty (..), nonEmpty, toList, reverse)
-import Data.Maybe
+import Data.List.NonEmpty (NonEmpty (..), toList, reverse, fromList)
 import Data.Set (Set)
 import Data.String
 import Data.Tree
 import GHC.Generics
 
-import Algebra.Graph.Internal
-
 import qualified Algebra.Graph.AdjacencyMap as AM
 import qualified Data.Set                   as Set
 
@@ -375,7 +372,7 @@ edgeCount = coerce AM.edgeCount
 -- vertexList1 . 'vertices1' == 'Data.List.NonEmpty.nub' . 'Data.List.NonEmpty.sort'
 -- @
 vertexList1 :: AdjacencyMap a -> NonEmpty a
-vertexList1 = unsafeNonEmpty . coerce AM.vertexList
+vertexList1 = fromList . coerce AM.vertexList
 
 -- | The sorted list of edges of a graph.
 -- Complexity: /O(n + m)/ time and /O(m)/ memory.

test/Algebra/Graph/Test/API.hs

@@ -55,7 +55,19 @@ instance Show g => Show (Mono g a) where
 toIntAPI :: API g Ord -> API g ((~) Int)
 toIntAPI API{..} = API{..}
 
--- TODO: Add missing API entries for Acyclic, NonEmpty and Symmetric graphs.
+-- TODO: Add missing API entries for Acyclic, NonEmpty and Symmetric
+--       graphs. Here is a blueprint initially discussed in
+--       https://github.com/snowleopard/alga/pull/250 (adding nonempty
+--       aims):
+--       1. Extend data API g c with new fields that correspond to
+--       missing methods (most of them end with the suffix 1).
+--       2. Add tests for missing methods to Test.Generic or
+--       Test.Generic.NonEmpty -- whichever turns out to be
+--       clearer/more convenient.
+--       3. Consider/decide whether or not ToGraph are useful or needed
+--       4. Tests for non-empty modules would need to import API,
+--       Generic and perhaps also Generic.NonEmpty (if it turns out to
+--       be convenient).
 -- | The complete graph API dictionary. A graph data type, such as 'G.Graph',
 -- typically implements only a part of the whole API.
 data API g c where