up n_m

node_modules/tiny-invariant/src/tiny-invariant.flow.js

@@ -0,0 +1,12 @@
+// @flow
+// This file is not actually executed
+// It is just used by flow for typing
+
+const prefix: string = 'Invariant failed';
+
+export default function invariant(condition: mixed, message?: string | (() => string)) {
+  if (condition) {
+    return;
+  }
+  throw new Error(`${prefix}: ${message || ''}`);
+}

node_modules/tiny-invariant/src/tiny-invariant.ts

@@ -0,0 +1,48 @@
+const isProduction: boolean = process.env.NODE_ENV === 'production';
+const prefix: string = 'Invariant failed';
+
+/**
+ * `invariant` is used to [assert](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#assertion-functions) that the `condition` is [truthy](https://github.com/getify/You-Dont-Know-JS/blob/bdbe570600d4e1107d0b131787903ca1c9ec8140/up%20%26%20going/ch2.md#truthy--falsy).
+ *
+ * 💥 `invariant` will `throw` an `Error` if the `condition` is [falsey](https://github.com/getify/You-Dont-Know-JS/blob/bdbe570600d4e1107d0b131787903ca1c9ec8140/up%20%26%20going/ch2.md#truthy--falsy)
+ *
+ * 🤏 `message`s are not displayed in production environments to help keep bundles small
+ *
+ * @example
+ *
+ * ```ts
+ * const value: Person | null = { name: 'Alex' };
+ * invariant(value, 'Expected value to be a person');
+ * // type of `value`` has been narrowed to `Person`
+ * ```
+ */
+export default function invariant(
+  condition: any,
+  // Not providing an inline default argument for message as the result is smaller
+  /**
+   * Can provide a string, or a function that returns a string for cases where
+   * the message takes a fair amount of effort to compute
+   */
+  message?: string | (() => string),
+): asserts condition {
+  if (condition) {
+    return;
+  }
+  // Condition not passed
+
+  // In production we strip the message but still throw
+  if (isProduction) {
+    throw new Error(prefix);
+  }
+
+  // When not in production we allow the message to pass through
+  // *This block will be removed in production builds*
+
+  const provided: string | undefined = typeof message === 'function' ? message() : message;
+
+  // Options:
+  // 1. message provided: `${prefix}: ${provided}`
+  // 2. message not provided: prefix
+  const value: string = provided ? `${prefix}: ${provided}` : prefix;
+  throw new Error(value);
+}