Add paramListOrNothing function

IHP/Controller/Param.hs

@@ -120,6 +120,37 @@ paramList name =
     |> DeepSeq.force
 {-# INLINABLE paramList #-}
 
+-- | Similiar to 'paramOrNothing' but works with multiple params. This is useful when submitting multiple
+-- input fields with the same name, and some may be empty.
+--
+-- Given a query like (note the `ingredients` in the middle that has no value):
+--
+-- > ingredients=milk&ingredients&ingredients=egg
+--
+-- This will return:
+--
+-- >>> paramListOrNothing @Text "ingredients"
+-- [Just "milk", Nothing, Just "egg"]
+--
+-- When no parameter with the name is given, an empty list is returned:
+--
+-- >>> paramListOrNothing @Text "not_given_in_url"
+-- []
+--
+--
+paramListOrNothing :: forall valueType. (?context :: ControllerContext, DeepSeq.NFData valueType, ParamReader valueType) => ByteString -> [Maybe valueType]
+paramListOrNothing name =
+    allParams
+    |> filter (\(paramName, paramValue) -> paramName == name)
+    |> mapMaybe (\(paramName, paramValue) -> paramValue)
+    |> map (\paramValue -> if paramValue == "" then Left "Empty ByteString" else readParameter @valueType paramValue)
+    |> map (\value -> case value of
+            Left _ -> Nothing
+            Right val -> Just val
+        )
+    |> DeepSeq.force
+{-# INLINABLE paramListOrNothing #-}
+
 paramParserErrorMessage name = "param: Parameter '" <> cs name <> "' is invalid"
 
 -- | Thrown when a parameter is missing when calling 'param "myParam"' or related functions
@@ -214,7 +245,7 @@ paramOrNothing !name =
 
 -- | Like 'param', but returns @Left "Some error message"@ if the parameter is missing or invalid
 paramOrError :: forall paramType. (?context :: ControllerContext) => ParamReader paramType => ByteString -> Either ParamException paramType
-paramOrError !name = 
+paramOrError !name =
     let
         RequestContext { requestBody } = ?context |> get #requestContext
     in case requestBody of

Test/Controller/ParamSpec.hs

@@ -85,6 +85,19 @@ tests = do
                 let ?context = createControllerContextWithParams []
                 (paramList @Int "numbers") `shouldBe` []
 
+        describe "paramListOrNothing" do
+            it "should parse valid input" do
+                let ?context = createControllerContextWithParams [("ingredients", "milk"), ("ingredients", ""), ("ingredients", "egg")]
+                (paramListOrNothing @Text "ingredients") `shouldBe` [Just "milk", Nothing, Just "egg"]
+
+            it "should not fail on invalid input" do
+                let ?context = createControllerContextWithParams [("numbers", "1"), ("numbers", "NaN")]
+                (paramListOrNothing @Int "numbers") `shouldBe` [Just 1, Nothing]
+
+            it "should deal with empty input" do
+                let ?context = createControllerContextWithParams []
+                (paramListOrNothing @Int "numbers") `shouldBe` []
+
         describe "hasParam" do
             it "returns True if param given" do
                 let ?context = createControllerContextWithParams [("a", "test")]
@@ -357,46 +370,46 @@ tests = do
         describe "fill" do
             it "should fill provided values if valid" do
                 let ?context = createControllerContextWithParams [("boolField", "on"), ("colorField", "Red")]
-                
+
                 let emptyRecord = FillRecord { boolField = False, colorField = Yellow, meta = def }
                 let expectedRecord = FillRecord { boolField = True, colorField = Red, meta = def { touchedFields = ["colorField", "boolField"] } }
-                
+
                 let filledRecord = emptyRecord |> fill @["boolField", "colorField"]
                 filledRecord `shouldBe` expectedRecord
-            
+
             it "should not touch fields if a field is missing" do
                 let ?context = createControllerContextWithParams [("colorField", "Red")]
-                
+
                 let emptyRecord = FillRecord { boolField = False, colorField = Yellow, meta = def }
                 let expectedRecord = FillRecord { boolField = False, colorField = Red, meta = def { touchedFields = ["colorField"] } }
-                
+
                 let filledRecord = emptyRecord |> fill @["boolField", "colorField"]
                 filledRecord `shouldBe` expectedRecord
 
             it "should add validation errors if the parsing fails" do
                 let ?context = createControllerContextWithParams [("colorField", "invalid color")]
-                
+
                 let emptyRecord = FillRecord { boolField = False, colorField = Yellow, meta = def }
                 let expectedRecord = FillRecord { boolField = False, colorField = Yellow, meta = def { annotations = [("colorField", TextViolation "Invalid value")] } }
-                
+
                 let filledRecord = emptyRecord |> fill @["boolField", "colorField"]
                 filledRecord `shouldBe` expectedRecord
-            
+
             it "should deal with json values" do
                 let ?context = createControllerContextWithJson "{\"colorField\":\"Red\",\"boolField\":true}"
-                
+
                 let emptyRecord = FillRecord { boolField = False, colorField = Yellow, meta = def }
                 let expectedRecord = FillRecord { boolField = True, colorField = Red, meta = def { touchedFields = ["colorField", "boolField"] } }
-                
+
                 let filledRecord = emptyRecord |> fill @["boolField", "colorField"]
                 filledRecord `shouldBe` expectedRecord
-            
+
             it "should deal with empty json values" do
                 let ?context = createControllerContextWithJson "{}"
-                
+
                 let emptyRecord = FillRecord { boolField = False, colorField = Yellow, meta = def }
                 let expectedRecord = FillRecord { boolField = False, colorField = Yellow, meta = def }
-                
+
                 let filledRecord = emptyRecord |> fill @["boolField", "colorField"]
                 filledRecord `shouldBe` expectedRecord