fix: allow any action payload if action was never typed (#5)

[fix] correct some minor TypeScript definition bugs * closes #4 - allow any event arguments if action types unspecified * expect event invocations to always returns State (string | symbol)
kenkunz · Dec 14, 2021 · e7c00ad · e7c00ad
1 parent e5ca666
commit e7c00ad
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Showing 2 changed files with 17 additions and 11 deletions.
diff --git a/index.d.ts b/index.d.ts
@@ -13,7 +13,11 @@ type LifecycleAction = (arg: {
   args: Args;
 }) => void;
 
-type ActionFunction = BaseState | ((...args: Args) => BaseState) | ((...args: Args) => void);
+type AllArgsAction = ((...args: Args) => BaseState)
+
+type VoidFunction = ((...args: Args) => void)
+
+type ActionFunction = BaseState | AllArgsAction | VoidFunction;
 
 type BaseActions = {
   _enter?: LifecycleAction;
@@ -29,8 +33,8 @@ type ExtractObjectValues<Object> = Object[keyof Object];
 
 type GetActionFunctionMapping<Actions extends BaseActions> = {
   [Key in Exclude<keyof Actions, '_enter' | '_exit'>]: Actions[Key] extends BaseState
-    ? () => Actions[Key]
-    : Actions[Key];
+    ? () => Actions[Key] extends void ? BaseState : Actions[Key]
+    : Actions[Key] extends VoidFunction ? ((...args: Parameters<Actions[Key]>) => BaseState) : Actions[Key]
 };
 
 type GetActionMapping<States extends BaseStates> = ExtractObjectValues<{
@@ -44,7 +48,7 @@ type Unsubscribe = () => void;
 type Subscribe<S extends BaseState> = (callback: (state: S) => void) => Unsubscribe;
 
 type StateMachine<State extends BaseState, Actions> = {
-  [Key in keyof Actions]: Actions[Key];
+  [Key in keyof Actions]: Actions[Key] | AllArgsAction;
 } & {
   subscribe: Subscribe<State>;
 };

diff --git a/test/types.ts b/test/types.ts
@@ -50,9 +50,11 @@ unsub();
 // @ts-expect-error state machine expects valid event invocation
 valid1.noSuchAction();
 
-// @ts-expect-error toggle expects no arguments (1 provided)
-valid1.toggle(1);
+// can pass any argument if action get's never typed
 valid1.toggle();
+valid1.toggle(1);
+valid1.toggle(true, 1);
+valid1.toggle("test", true, 1);
 
 const toggleResultValid: string | symbol = valid1.toggle();
 // @ts-expect-error toggle returns string or symbol
@@ -88,13 +90,13 @@ valid3.overloaded('string', 2);
 // @ts-expect-error overloaded expects 1 or 2 args (3 provided)
 valid3.overloaded(1, 2, 3);
 
-// @ts-expect-error overloaded with single argument returns string | void
+// @ts-expect-error overloaded with single argument returns string | symbol
 const overloadedResult1Invalid: void = valid3.overloaded(1);
-const overloadedResult1Valid: string | void = valid3.overloaded(1);
+const overloadedResult1Valid: string | symbol = valid3.overloaded(1);
 
-// @ts-expect-error overloaded with two arguments returns only void
-const overloadedResult2Invalid: string = valid3.overloaded('string', 1);
-const overloadedResult2Valid: string | void = valid3.overloaded('string', 1);
+// @ts-expect-error overloaded with two arguments returns string | symbol
+const overloadedResult2Invalid: void = valid3.overloaded('string', 1);
+const overloadedResult2Valid: string | symbol = valid3.overloaded('string', 1);
 
 // A state machine that uses symbols as a state keys
 const valid4 = fsm(Symbol.for('foo'), {