Parse interface type definition

src/Language/GraphQL/AST/Parser.hs

@@ -38,6 +38,7 @@ typeSystemDefinition = schemaDefinition
 typeDefinition :: Parser TypeDefinition
 typeDefinition = scalarTypeDefinition
     <|> objectTypeDefinition
+    <|> interfaceTypeDefinition
     <|> unionTypeDefinition
     <?> "TypeDefinition"
 
@@ -83,6 +84,15 @@ unionMemberTypes sepBy' = UnionMemberTypes
     <*> name `sepBy'` pipe
     <?> "UnionMemberTypes"
 
+interfaceTypeDefinition :: Parser TypeDefinition
+interfaceTypeDefinition = InterfaceTypeDefinition
+    <$> description
+    <* symbol "interface"
+    <*> name
+    <*> opt directives
+    <*> braces (many fieldDefinition)
+    <?> "InterfaceTypeDefinition"
+
 implementsInterfaces ::
     Foldable t =>
     (Parser Text -> Parser Text -> Parser (t NamedType)) ->

src/Language/GraphQL/Schema.hs

@@ -94,7 +94,7 @@ resolveFieldValue f resolveRight fld@(Field _ _ args _) = do
             _ <- addErrMsg err
             return $ HashMap.singleton (aliasOrName fld) Aeson.Null
 
--- | Helper function to facilitate 'Argument' handling.
+-- | Helper function to facilitate error handling and result emitting.
 withField :: (MonadIO m, Aeson.ToJSON a)
     => CollectErrsT m a -> Field -> CollectErrsT m (HashMap Text Aeson.Value)
 withField v fld

tests/Language/GraphQL/AST/ParserSpec.hs

@@ -74,3 +74,10 @@ spec = describe "Parser" $ do
         parse document "" `shouldSucceedOn` [r|
             union SearchResult = Photo | Person
         |]
+
+    it "parses minimal interface type definition" $
+        parse document "" `shouldSucceedOn` [r|
+            interface NamedEntity {
+              name: String
+            }
+        |]