Correct error for missing delegate field

lib/liquid_voting_web/resolvers/delegations.ex

@@ -8,16 +8,51 @@ defmodule LiquidVotingWeb.Resolvers.Delegations do
   def delegation(_, %{id: id}, %{context: %{organization_id: organization_id}}),
     do: {:ok, Delegations.get_delegation!(id, organization_id)}
 
-  # Will add participants to the db if they don't exist yet, or fetch them if they do. 
-  # Their ids are used for delegator_id and delegate_id when inserting the delegation
-  # with create_delegation_with_valid_arguments/1
+  @doc """
+  Creates a delegation.
+
+  Adds participants to the db if they don't exist, or fetches them if they do.
+
+  Valid arguments (args) must include 2 ids (delegator_id and delegate_id)
+  OR 2 emails (delegator_email and delegate_email).
+
+  Valid arguments (args) may include a proposal_url.
+  Without a proposal_url, an attempt to create a global delegation will occur.
+
+  The participant ids, either directly taken from delegator_id and
+  delegate_id, or via searching the db for participants with the emails
+  provided, are used when inserting the delegation with
+  LiquidVoting.Delegations.create_delegation/1.
+
+  ## Examples
+
+  iex> create_delegation(
+    %{},
+    %{delegator_email: "alice@somemail.com",
+    delegate_email: "bob@somemail.com",
+    proposal_url: "https://proposalplace/proposal63"},
+    %{context: %{organization_id: "b212ef83-d3df-4a7a-8875-36cca613e8d6"}})
+  %Delegation{}
+
+  iex> create_delegation(
+    %{},
+    %{delegator_email: "alice@somemail.com"},
+    %{context: %{organization_id: "b212ef83-d3df-4a7a-8875-36cca613e8d6"}})
+  {:error,                                                   
+    %{
+      details: %{delegate_email: ["can't be blank"]},
+      message: "Could not create delegation"
+    }}
+  """
   def create_delegation(_, args, %{context: %{organization_id: organization_id}}) do
-    args
-    |> Map.put(:organization_id, organization_id)
-    |> Delegations.create_delegation()
-    |> case do
-      {:ok, delegation} ->
-        {:ok, delegation}
+    args = Map.put(args, :organization_id, organization_id)
+
+    with {:ok, args} <- validate_participant_args(args),
+         {:ok, delegation} <- Delegations.create_delegation(args) do
+      {:ok, delegation}
+    else
+      {:error, %{message: message, details: details}} ->
+        {:error, %{message: message, details: details}}
 
       {:error, changeset} ->
         {:error,
@@ -29,6 +64,44 @@ defmodule LiquidVotingWeb.Resolvers.Delegations do
     end
   end
 
+  defp validate_participant_args(args) do
+    case args do
+      %{delegator_email: _, delegate_email: _} ->
+        {:ok, args}
+
+      %{delegator_id: _, delegate_id: _} ->
+        {:ok, args}
+
+      # delegator_email field provided, but no delegate_email field provided
+      %{delegator_email: _} ->
+        field_not_found_error(%{delegate_email: ["can't be blank"]})
+
+      # delegate_email field provided, but no delegator_email field provided
+      %{delegate_email: _} ->
+        field_not_found_error(%{delegator_email: ["can't be blank"]})
+
+      # delegator_id field provided, but no delegate_id field provided
+      %{delegator_id: _} ->
+        field_not_found_error(%{delegate_id: ["can't be blank"]})
+
+      # delegate_id field provided, but no delegator_id field provided
+      %{delegate_id: _} ->
+        field_not_found_error(%{delegator_id: ["can't be blank"]})
+
+      # no id or email fields provided for delegator and delegate
+      _ ->
+        field_not_found_error("emails or ids identifying delegator and delegate can't be blank")
+    end
+  end
+
+  defp field_not_found_error(details) do
+    {:error,
+     %{
+       message: "Could not create delegation",
+       details: details
+     }}
+  end
+
   # Delete proposal-specific delegations
   def delete_delegation(
         _,

test/liquid_voting/delegations_test.exs

@@ -60,8 +60,7 @@ defmodule LiquidVoting.DelegationsTest do
       assert {:error, %Ecto.Changeset{}} = Delegations.create_delegation(context[:invalid_attrs])
     end
 
-    test "create_delegation/1 with same participant as delegator and delegate returns error changeset",
-         context do
+    test "create_delegation/1 with same participant as delegator and delegate returns error changeset" do
       participant = insert(:participant)
 
       args = %{

test/liquid_voting_web/absinthe/mutations/create_delegation_test.exs

@@ -89,7 +89,7 @@ defmodule LiquidVotingWeb.Absinthe.Mutations.CreateDelegationTest do
       assert delegation["votingResult"]["against"] == 0
     end
 
-    test "with missing fields" do
+    test "with missing delegate email field" do
       query = """
       mutation {
         createDelegation(delegatorEmail: "#{@delegator_email}") {
@@ -109,7 +109,7 @@ defmodule LiquidVotingWeb.Absinthe.Mutations.CreateDelegationTest do
         Absinthe.run(query, Schema, context: %{organization_id: Ecto.UUID.generate()})
 
       assert message == "Could not create delegation"
-      assert details == %{delegate_id: ["can't be blank"], delegator_id: ["can't be blank"]}
+      assert details == %{delegate_email: ["can't be blank"]}
     end
   end
 
@@ -170,7 +170,28 @@ defmodule LiquidVotingWeb.Absinthe.Mutations.CreateDelegationTest do
       assert delegation["delegate"]["email"] == context[:delegate].email
     end
 
-    test "with missing field", context do
+    test "with proposal url, but missing delegate and delegator id fields" do
+      query = """
+      mutation {
+        createDelegation(proposalUrl: "#{@proposal_url}") {
+          delegator {
+            email
+          }
+          delegate {
+            email
+          }
+        }
+      }
+      """
+
+      {:ok, %{errors: [%{message: message, details: details}]}} =
+        Absinthe.run(query, Schema, context: %{organization_id: Ecto.UUID.generate()})
+
+      assert message == "Could not create delegation"
+      assert details == "emails or ids identifying delegator and delegate can't be blank"
+    end
+
+    test "with missing delegate id field", context do
       query = """
       mutation {
         createDelegation(delegatorId: "#{context[:delegator].id}") {