Feat/mutation error policy

README.md

@@ -181,22 +181,34 @@ module ScreamMutation = [%graphql {|
 [@react.component]
 let make = () => {
   /* Both variant and records available */
-  let ( screamMutation, _simple, _full ) = useMutation(~variables=ScreamMutation.makeVariables(~screamLevel=10, ()), ScreamMutation.definition);
+  let ( screamMutation, simple, _full ) =
+    useMutation(~variables=ScreamMutation.makeVariables(~screamLevel=10, ()), ScreamMutation.definition);
   let scream = (_) => {
     screamMutation()
-      |> Js.Promise.then_(result => {
-          switch(result) {
-            | Data(data) => ...
-            | Error(error) => ...
-            | NoData => ...
-          }
-          Js.Promise.resolve()
-        })
+      |> Js.Promise.then_(((simple, _full)) => {
+           // Trigger side effects by chaining the promise returned by screamMutation()
+           switch (simple) {
+             // You *must* set the error policy to be able to handle errors
+             // in then_. See EditPersons.re for more
+           | ApolloHooks.Mutation.Errors(_theErrors) => Js.log("OH NO!")
+           | NoData => Js.log("NO DATA?")
+           | Data(_theData) => Js.log("DATA!")
+           };
+           Js.Promise.resolve();
+         })
       |> ignore
   }
 
+  // Use simple (and/or full) for (most) UI feedback
   <div>
-    <button onClick={scream}>
+    {switch (simple) {
+     | NotCalled
+     | Data(_) => React.null
+     | Loading => <div> "Screaming!"->React.string </div>
+     | NoData
+     | Error(_) => <div> "Something went wrong!"->React.string </div>
+     }}
+    <button onClick={scream} disabled={simple === Loading}>
       {React.string("You kids get off my lawn!")}
     </button>
   </div>
@@ -212,14 +224,9 @@ let make = () => {
   let ( screamMutation, _simple, _full ) = useMutation(ScreamMutation.definition);
   let scream = (_) => {
     screamMutation(~variables=ScreamMutation.makeVariables(~screamLevel=10, ()), ())
-      |> Js.Promise.then_(result => {
-          switch(result) {
-            | Data(data) => ...
-            | Error(error) => ...
-            | NoData => ...
-          }
-          Js.Promise.resolve()
-        })
+      |> Js.Promise.then_(((simple, _full)) => {
+           ...
+         })
       |> ignore
   }
 

examples/persons/src/EditPerson.re

@@ -71,7 +71,12 @@ let make = (~refetchQueries, ~update) => {
     React.useReducer(reducer, {age: None, name: "", id: ""});
 
   let (editPersonMutation, _simple, _full) =
-    useMutation(~refetchQueries, ~update, EditPersonMutation.definition);
+    useMutation(
+      ~refetchQueries,
+      ~update,
+      ~errorPolicy=All, // See note below on error policies
+      EditPersonMutation.definition,
+    );
 
   let handleSubmit = event => {
     ReactEvent.Form.preventDefault(event);
@@ -89,8 +94,26 @@ let make = (~refetchQueries, ~update) => {
           OptimisticResponse.make(~id=state.id, ~name=state.name, ~age),
         (),
       )
+      /* Setting error policy to All (or Ignore) means that errors show up
+       * in then_ in the promise returned by editPersonMutation
+       * Not setting it (or setting it to None) makes the promise reject
+       * on errors and you'll have to handle errors in Js.catch(e => ...) instead,
+       * where e is just Js.Promise.error and you won't get any help from the type system.
+       *
+       * See also: https://www.apollographql.com/docs/react/data/error-handling/#error-policies
+       */
+      |> Js.Promise.then_(((simple, _full) as result) => {
+           switch (simple) {
+           | ApolloHooks.Mutation.Errors(_theErrors) => Js.log("OH NO!")
+           | NoData => Js.log("NO DATA?")
+           | Data(_theData) => Js.log("DATA!")
+           };
+           // If you don't need to handle the result elsewhere,
+           // the promise can just resolve to unit
+           Js.Promise.resolve(result);
+         })
       |> ignore
-    | None => ignore()
+    | None => ()
     };
   };
 

src/ApolloHooksMutation.re

@@ -64,6 +64,8 @@ type options('a) = {
   [@bs.optional]
   optimisticResponse: Js.Json.t,
   [@bs.optional]
+  errorPolicy: string,
+  [@bs.optional]
   context: Context.t,
 };
 
@@ -97,6 +99,7 @@ let useMutation:
              unit
                =?,
     ~optimisticResponse: Js.Json.t=?,
+    ~errorPolicy: ApolloHooksTypes.errorPolicy=?,
     ~context: Context.t=?,
     ApolloHooksTypes.graphqlDefinition('data, _, _)
   ) =>
@@ -112,6 +115,7 @@ let useMutation:
     ~awaitRefetchQueries=?,
     ~update=?,
     ~optimisticResponse=?,
+    ~errorPolicy=?,
     ~context=?,
     (parse, query, _),
   ) => {
@@ -125,6 +129,8 @@ let useMutation:
           ~awaitRefetchQueries?,
           ~update?,
           ~optimisticResponse?,
+          ~errorPolicy=?
+            errorPolicy->Belt.Option.map(ApolloHooksTypes.errorPolicyToJs),
           ~context?,
           (),
         ),