Add operation type encoder

CHANGELOG.md

@@ -16,6 +16,9 @@ and this project adheres to
 - `Language.GraphQL`: Added information about the *json* flag and switching to
   *graphql-spice* for JSON support.
 
+### Added
+- Partial schema printing: operation type encoder.
+
 ## [1.0.3.0] - 2022-03-27
 ### Fixed
 - Index position in error path. (Index and Segment paths of a field have been

src/Language/GraphQL/AST/Encoder.hs

@@ -11,6 +11,7 @@ module Language.GraphQL.AST.Encoder
     , directive
     , document
     , minified
+    , operationType
     , pretty
     , type'
     , value
@@ -34,7 +35,7 @@ import qualified Language.GraphQL.AST.Document as Full
 --   Use 'pretty' or 'minified' to construct the formatter.
 data Formatter
     = Minified
-    | Pretty Word
+    | Pretty !Word
 
 -- | Constructs a formatter for pretty printing.
 pretty :: Formatter
@@ -294,6 +295,12 @@ nonNullType :: Full.NonNullType -> Lazy.Text
 nonNullType (Full.NonNullTypeNamed x) = Lazy.Text.fromStrict x <> "!"
 nonNullType (Full.NonNullTypeList x) = listType x <> "!"
 
+-- | Produces lowercase operation type: query, mutation or subscription.
+operationType :: Formatter -> Full.OperationType -> Lazy.Text
+operationType _formatter Full.Query = "query"
+operationType _formatter Full.Mutation = "mutation"
+operationType _formatter Full.Subscription = "subscription"
+
 -- * Internal
 
 between :: Char -> Char -> Lazy.Text -> Lazy.Text

tests/Language/GraphQL/AST/EncoderSpec.hs

@@ -173,3 +173,8 @@ spec = do
                 |] '\n'
                 actual = definition pretty operation
              in actual `shouldBe` expected
+
+    describe "operationType" $
+        it "produces lowercase mutation operation type" $
+            let actual = operationType pretty Full.Mutation
+             in actual `shouldBe` "mutation"