Handle recursive objects by wrapping them in a newtype

miniBill · miniBill · commit bc3556e0ef4f · 2026-05-09T18:28:01.000+02:00
diff --git a/cli/example/recursive.yaml b/cli/example/recursive.yaml
@@ -0,0 +1,16 @@
+openapi: 3.0.1
+info:
+    title: "Recursive"
+    version: "1"
+components:
+    schemas:
+        Recursive:
+            description: Recursive type
+            type: object
+            properties:
+                date:
+                    type: string
+                    format: date
+                parent:
+                    description: Tag information
+                    $ref: "#/components/schemas/Recursive"
diff --git a/cli/example/src/Example.elm b/cli/example/src/Example.elm
@@ -18,6 +18,8 @@ import PatreonApi.Api
 import PatreonApi.Types.Responses
 import RealworldConduitApi.Api
 import RealworldConduitApi.Types.Responses
+import Recursive.Json
+import Recursive.Types
 import RecursiveAllofRefs.Types
 import SimpleRef.Json
 import SingleEnum.Types
@@ -49,6 +51,9 @@ init () =
 
         _ =
             MultipartFormData.Api.api
+
+        _ =
+            Recursive.Json.encodeRecursive
     in
     ( {}
     , Cmd.batch
diff --git a/cli/src/TestGenScript.elm b/cli/src/TestGenScript.elm
@@ -89,6 +89,10 @@ run =
         realworldConduit =
             OpenApi.Config.inputFrom (OpenApi.Config.File "./example/realworld-conduit.yaml")
 
+        recursive : OpenApi.Config.Input
+        recursive =
+            OpenApi.Config.inputFrom (OpenApi.Config.File "./example/recursive.yaml")
+
         recursiveAllOfRefs : OpenApi.Config.Input
         recursiveAllOfRefs =
             OpenApi.Config.inputFrom (OpenApi.Config.File "./example/recursive-allof-refs.yaml")
@@ -149,6 +153,7 @@ run =
                 |> OpenApi.Config.withInput overridingGlobalSecurity
                 |> OpenApi.Config.withInput pathLevelParams
                 |> OpenApi.Config.withInput realworldConduit
+                |> OpenApi.Config.withInput recursive
                 |> OpenApi.Config.withInput recursiveAllOfRefs
                 |> OpenApi.Config.withInput simpleRef
                 |> OpenApi.Config.withInput singleEnum
diff --git a/review/suppressed/NoUnused.Exports.json b/review/suppressed/NoUnused.Exports.json
@@ -3,7 +3,7 @@
   "automatically created by": "elm-review suppress",
   "learn more": "elm-review suppress --help",
   "suppressions": [
-    { "count": 1, "filePath": "src/CliMonad.elm" },
+    { "count": 2, "filePath": "src/CliMonad.elm" },
     { "count": 1, "filePath": "src/OpenApi/Common/Internal.elm" }
   ]
 }
diff --git a/src/CliMonad.elm b/src/CliMonad.elm
@@ -3,8 +3,8 @@ module CliMonad exposing
     , run, stepOrFail
     , succeed, succeedWith, fail, fromResult
     , map, map2, map3
-    , andThen, andThen2, andThen3, andThen4, combine, combineDict, combineMap, foldl
-    , errorToWarning, getApiSpec, enumName, moduleToNamespace, getOrCache
+    , andThen, andThen2, andThen3, andThen4, combine, combineDict, combineMap, foldl, any, findMap
+    , errorToWarning, getApiSpec, enumName, moduleToNamespace, getOrCacheIsRecursive, getOrCacheType
     , withPath, withWarning, withExtendedWarning, withRequiredPackage
     , todo, todoWithDefault
     , withFormat
@@ -18,8 +18,8 @@ module CliMonad exposing
 @docs run, stepOrFail
 @docs succeed, succeedWith, fail, fromResult
 @docs map, map2, map3
-@docs andThen, andThen2, andThen3, andThen4, combine, combineDict, combineMap, foldl
-@docs errorToWarning, getApiSpec, enumName, moduleToNamespace, getOrCache
+@docs andThen, andThen2, andThen3, andThen4, combine, combineDict, combineMap, foldl, any, findMap
+@docs errorToWarning, getApiSpec, enumName, moduleToNamespace, getOrCacheIsRecursive, getOrCacheType
 @docs withPath, withWarning, withExtendedWarning, withRequiredPackage
 @docs todo, todoWithDefault
 @docs withFormat
@@ -99,7 +99,9 @@ type CliMonad a
 
 
 type alias Cache =
-    FastDict.Dict String Common.Type
+    { typeCache : FastDict.Dict String Common.Type
+    , isRecursiveCache : FastDict.Dict String (Maybe Common.UnsafeName)
+    }
 
 
 type alias Output =
@@ -200,26 +202,54 @@ run oneOfDeclarations input (CliMonad x) =
 
 emptyCache : Cache
 emptyCache =
-    FastDict.empty
+    { typeCache = FastDict.empty
+    , isRecursiveCache = FastDict.empty
+    }
+
+
+getOrCacheType : Common.RefTo Common.Schema -> (() -> CliMonad Common.Type) -> CliMonad Common.Type
+getOrCacheType ref compute =
+    let
+        (Common.UnsafeName key) =
+            Common.refToString ref
+    in
+    CliMonad
+        (\input cache ->
+            case FastDict.get key cache.typeCache of
+                Nothing ->
+                    let
+                        (CliMonad inner) =
+                            compute ()
+                    in
+                    case inner input cache of
+                        Ok ( computed, output, cache2 ) ->
+                            Ok ( computed, output, { cache2 | typeCache = FastDict.insert key computed cache2.typeCache } )
+
+                        Err e ->
+                            Err e
+
+                Just found ->
+                    Ok ( found, emptyOutput, cache )
+        )
 
 
-getOrCache : Common.RefTo Common.Schema -> (() -> CliMonad Common.Type) -> CliMonad Common.Type
-getOrCache ref compute =
+getOrCacheIsRecursive : Common.RefTo Common.Schema -> (() -> CliMonad (Maybe Common.UnsafeName)) -> CliMonad (Maybe Common.UnsafeName)
+getOrCacheIsRecursive ref compute =
     let
         (Common.UnsafeName key) =
             Common.refToString ref
     in
     CliMonad
         (\input cache ->
-            case FastDict.get key cache of
+            case FastDict.get key cache.isRecursiveCache of
                 Nothing ->
                     let
                         (CliMonad inner) =
                             compute ()
                     in
                     case inner input cache of
                         Ok ( computed, output, cache2 ) ->
-                            Ok ( computed, output, FastDict.insert key computed cache2 )
+                            Ok ( computed, output, { cache2 | isRecursiveCache = FastDict.insert key computed cache2.isRecursiveCache } )
 
                         Err e ->
                             Err e
@@ -443,6 +473,49 @@ map4 f (CliMonad x) (CliMonad y) (CliMonad z) (CliMonad w) =
         )
 
 
+any : (a -> CliMonad Bool) -> List a -> CliMonad Bool
+any f xs =
+    CliMonad
+        (\input cache ->
+            Result.Extra.foldlWhileOk
+                (\x ( a, o, c ) ->
+                    if a then
+                        Ok ( a, o, c )
+
+                    else
+                        let
+                            (CliMonad i) =
+                                f x
+                        in
+                        i input c
+                )
+                ( False, emptyOutput, cache )
+                xs
+        )
+
+
+findMap : (a -> CliMonad (Maybe b)) -> List a -> CliMonad (Maybe b)
+findMap f xs =
+    CliMonad
+        (\input cache ->
+            Result.Extra.foldlWhileOk
+                (\x ( a, o, c ) ->
+                    case a of
+                        Just _ ->
+                            Ok ( a, o, c )
+
+                        Nothing ->
+                            let
+                                (CliMonad i) =
+                                    f x
+                            in
+                            i input c
+                )
+                ( Nothing, emptyOutput, cache )
+                xs
+        )
+
+
 andThen : (a -> CliMonad b) -> CliMonad a -> CliMonad b
 andThen f (CliMonad x) =
     CliMonad
diff --git a/src/Common.elm b/src/Common.elm
@@ -446,7 +446,7 @@ initialUppercaseWordToLowercase input =
 
 type Type
     = Nullable Type
-    | Object Object
+    | Object { isRecursive : Maybe UnsafeName } Object
     | Basic
         -- This is separate for easier pattern matching
         BasicType
diff --git a/src/Elm/Extra.elm b/src/Elm/Extra.elm
@@ -1,4 +1,4 @@
-module Elm.Extra exposing (functionReduced)
+module Elm.Extra exposing (functionReduced, withDocumentationMaybe)
 
 import Elm
 import Elm.ToString
@@ -12,3 +12,13 @@ functionReduced argName f =
 
     else
         Elm.functionReduced argName f
+
+
+withDocumentationMaybe : Maybe String -> Elm.Declaration -> Elm.Declaration
+withDocumentationMaybe documentation declaration =
+    case documentation of
+        Nothing ->
+            declaration
+
+        Just doc ->
+            Elm.withDocumentation doc declaration
diff --git a/src/Gen/BackendTask.elm b/src/Gen/BackendTask.elm
@@ -5,8 +5,6 @@ module Gen.BackendTask exposing (annotation_)
 
 # Generated bindings for BackendTask
 
-@docs map
-@docs map56
 @docs annotation_
 
 -}
diff --git a/src/Gen/Json/Decode.elm b/src/Gen/Json/Decode.elm
@@ -3,7 +3,7 @@ module Gen.Json.Decode exposing
     , list, dict, keyValuePairs, field
     , index, oneOf
     , map, map2, map3
-    , value, null
+    , lazy, value, null
     , succeed, fail, andThen, annotation_
     , call_, values_
     )
@@ -17,7 +17,7 @@ module Gen.Json.Decode exposing
 @docs list, dict, keyValuePairs, field
 @docs index, oneOf
 @docs map, map2, map3
-@docs value, null
+@docs lazy, value, null
 @docs succeed, fail, andThen, annotation_
 @docs call_, values_
 
@@ -596,6 +596,64 @@ map3 map3Arg_ map3Arg_0 map3Arg_1 map3Arg_2 =
         ]
 
 
+{-| Sometimes you have JSON with recursive structure, like nested comments.
+You can use `lazy` to make sure your decoder unrolls lazily.
+
+    type alias Comment =
+        { message : String
+        , responses : Responses
+        }
+
+    type Responses
+        = Responses (List Comment)
+
+    comment : Decoder Comment
+    comment =
+        map2 Comment
+            (field "message" string)
+            (field "responses" (map Responses (list (lazy (\_ -> comment)))))
+
+If we had said `list comment` instead, we would start expanding the value
+infinitely. What is a `comment`? It is a decoder for objects where the
+`responses` field contains comments. What is a `comment` though? Etc.
+
+By using `list (lazy (\_ -> comment))` we make sure the decoder only expands
+to be as deep as the JSON we are given. You can read more about recursive data
+structures [here].
+
+[here]: https://github.com/elm/compiler/blob/master/hints/recursive-alias.md
+
+lazy: (() -> Json.Decode.Decoder a) -> Json.Decode.Decoder a
+
+-}
+lazy : (Elm.Expression -> Elm.Expression) -> Elm.Expression
+lazy lazyArg_ =
+    Elm.apply
+        (Elm.value
+            { importFrom = [ "Json", "Decode" ]
+            , name = "lazy"
+            , annotation =
+                Just
+                    (Type.function
+                        [ Type.function
+                            [ Type.unit ]
+                            (Type.namedWith
+                                [ "Json", "Decode" ]
+                                "Decoder"
+                                [ Type.var "a" ]
+                            )
+                        ]
+                        (Type.namedWith
+                            [ "Json", "Decode" ]
+                            "Decoder"
+                            [ Type.var "a" ]
+                        )
+                    )
+            }
+        )
+        [ Elm.functionReduced "lazyUnpack" lazyArg_ ]
+
+
 {-| Do not do anything with a JSON value, just bring it into Elm as a `Value`.
 This can be useful if you have particularly complex data that you would like to
 deal with later. Or if you are going to send it out a port and do not care
diff --git a/src/JsonSchema/Generate.elm b/src/JsonSchema/Generate.elm
diff --git a/src/OpenApi/Generate.elm b/src/OpenApi/Generate.elm
diff --git a/src/SchemaUtils.elm b/src/SchemaUtils.elm
diff --git a/tests/Test/OpenApi/Generate.elm b/tests/Test/OpenApi/Generate.elm

Original file line number	Diff line number	Diff line change
`@@ -3,7 +3,7 @@`
`3`	`3`	`"automatically created by": "elm-review suppress",`
`4`	`4`	`"learn more": "elm-review suppress --help",`
`5`	`5`	`"suppressions": [`
`6`		`- { "count": 1, "filePath": "src/CliMonad.elm" },`
	`6`	`+ { "count": 2, "filePath": "src/CliMonad.elm" },`
`7`	`7`	`{ "count": 1, "filePath": "src/OpenApi/Common/Internal.elm" }`
`8`	`8`	`]`
`9`	`9`	`}`