test: provide a static type checking against example usages

test/typecheck.action.ts

@@ -0,0 +1,174 @@
+/*
+ *                            *** MIT LICENSE ***
+ * -------------------------------------------------------------------------
+ * This code may be modified and distributed under the MIT license.
+ * See the LICENSE file for details.
+ * -------------------------------------------------------------------------
+ *
+ * @summary   A test for the typescript definition
+ *
+ * @author    Alvis HT Tang <alvis@hilbert.space>
+ * @license   MIT
+ * @copyright Copyright (c) 2018 - All Rights Reserved.
+ * -------------------------------------------------------------------------
+ */
+
+import { Action, ErroneousAction, StandardAction } from '../definitions';
+
+//
+// Action Type
+//
+
+const TEST_TYPE = 'type';
+type TestType = typeof TEST_TYPE;
+
+interface TestPayload {
+  data: 'payload';
+}
+
+interface TestMeta {
+  data: 'meta';
+}
+
+{
+  const action: StandardAction = {
+    type: TEST_TYPE
+  };
+}
+
+{
+  const action: ErroneousAction = {
+    type: TEST_TYPE,
+    payload: new Error('message'),
+    error: true
+  };
+}
+
+/* ----- Action ----- */
+
+// The Action type should cover all types above.
+
+{
+  const action: Action = {
+    type: TEST_TYPE
+  };
+
+  {
+    // would fail if test is 'type' instread of string
+    const test: string = action.type;
+  }
+
+  {
+    // would fail if test is in ErroneousAction type
+    const test: StandardAction = action;
+  }
+}
+
+{
+  const action: Action<TestType> = {
+    type: TEST_TYPE
+  };
+  {
+    // now action.type can be in the type of 'type'
+    const test: TestType = action.type;
+  }
+
+  {
+    // would fail if test is in ErroneousAction type
+    const test: StandardAction<TestType> = action;
+  }
+}
+
+{
+  const action: Action<TestType> = {
+    type: TEST_TYPE
+  };
+  {
+    const test: TestType = action.type;
+  }
+
+  {
+    // should pass with any the type for Payload and Meta
+    const test: StandardAction<TestType, any, any> = action;
+  }
+}
+
+{
+  const action: Action<TestType, TestPayload, TestMeta> = {
+    type: TEST_TYPE,
+    payload: {
+      data: 'payload'
+    },
+    meta: {
+      data: 'meta'
+    }
+  };
+  {
+    const test: TestType = action.type;
+  }
+
+  {
+    // should pass with any the type for Payload and Meta
+    const test: StandardAction<TestType, any, any> = action;
+  }
+}
+
+{
+  const action: Action<TestType, TestPayload, TestMeta> = {
+    type: TEST_TYPE,
+    payload: {
+      data: 'payload'
+    },
+    meta: {
+      data: 'meta'
+    }
+  };
+
+  // would fail if test is in ErroneousAction type
+  const test: StandardAction<TestType, TestPayload, TestMeta> = action;
+}
+
+{
+  const action: Action = {
+    type: TEST_TYPE,
+    payload: new Error('message'),
+    error: true
+  };
+
+  // would fail if test is in StandardAction type
+  const test: ErroneousAction = action;
+}
+
+{
+  let action: Action;
+
+  {
+    const test: boolean = action.error;
+  }
+
+  if (action.error === true) {
+    // would fail if test is in StandardAction type
+    const test: ErroneousAction = action;
+  } else {
+    // would fail if test is in ErroneousAction type
+    const test: StandardAction = action;
+  }
+}
+
+{
+  let action: Action<TestType, TestPayload, TestMeta>;
+
+  {
+    const test: boolean = action.error;
+  }
+
+  if (action.error === true) {
+    // would fail if test is in StandardAction type
+    const test: ErroneousAction<TestType, TestMeta> = action;
+  } else {
+    // would fail if test is in ErroneousAction type
+    const test: StandardAction<TestType, TestPayload, TestMeta> = action;
+  }
+}
+
+// ---------------------------------------- //