[wb1812.2.idcomponent] Add the Id component (#2389)

## Summary: This adds a simple CaaF (children-as-a-function) component to generate unique IDs as a stand-in for the `useId` hook. This is useful for cases where one needs to generate unique IDs for a component, but cannot use the hook without a larger refactor. Issue: WB-1812 ## Test plan: `yarn test` `yarn start:storybook` to check for the added docs `yarn typecheck` Author: somewhatabstract Reviewers: jeresig Required Reviewers: Approved By: jeresig Checks: ⌛ Prime node_modules cache for primary configuration (ubuntu-latest, 20.x), ⌛ Check for .changeset entries for all changed files (ubuntu-latest, 20.x), ⌛ gerald, ⏭️ dependabot Pull Request URL: #2389
Khan · Dec 16, 2024 · 897686b · 897686b
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diff --git a/.changeset/thirty-jars-grow.md b/.changeset/thirty-jars-grow.md
@@ -0,0 +1,5 @@
+---
+"@khanacademy/wonder-blocks-core": minor
+---
+
+-   Add the `Id` component for cases where `useId` cannot be used directly
diff --git a/__docs__/wonder-blocks-core/id.stories.tsx b/__docs__/wonder-blocks-core/id.stories.tsx
@@ -0,0 +1,46 @@
+import * as React from "react";
+
+import {Meta} from "@storybook/react";
+import {View, Id} from "@khanacademy/wonder-blocks-core";
+import {Body, BodyMonospace} from "@khanacademy/wonder-blocks-typography";
+import {Strut} from "@khanacademy/wonder-blocks-layout";
+import {spacing} from "@khanacademy/wonder-blocks-tokens";
+
+export default {
+    title: "Packages / Core / Id",
+
+    parameters: {
+        chromatic: {
+            // We don't need a snapshot for this.
+            disableSnapshot: true,
+        },
+    },
+} as Meta;
+
+export const GeneratedIdExample = () => (
+    <View>
+        <Id>
+            {(id) => (
+                <View style={{flexDirection: "row"}}>
+                    <Body>Generated identifier: </Body>
+                    <Strut size={spacing.xSmall_8} />
+                    <BodyMonospace>{id}</BodyMonospace>
+                </View>
+            )}
+        </Id>
+    </View>
+);
+
+export const PassedThroughIdExample = () => (
+    <View>
+        <Id id="my-identifier">
+            {(id) => (
+                <View style={{flexDirection: "row"}}>
+                    <Body>Passed through identifier: </Body>
+                    <Strut size={spacing.xSmall_8} />
+                    <BodyMonospace>{id}</BodyMonospace>
+                </View>
+            )}
+        </Id>
+    </View>
+);
diff --git a/packages/wonder-blocks-core/src/components/__tests__/id.test.tsx b/packages/wonder-blocks-core/src/components/__tests__/id.test.tsx
@@ -0,0 +1,28 @@
+import * as React from "react";
+
+import {render} from "@testing-library/react";
+import {Id} from "../id";
+
+describe("Id", () => {
+    it("should provide an id to the children", () => {
+        // Arrange
+        const childrenFn = jest.fn().mockReturnValue(null);
+
+        // Act
+        render(<Id>{childrenFn}</Id>);
+
+        // Assert
+        expect(childrenFn).toHaveBeenCalledWith(expect.any(String));
+    });
+
+    it("should pass through the given id to the children", () => {
+        // Arrange
+        const childrenFn = jest.fn().mockReturnValue(null);
+
+        // Act
+        render(<Id id="my-id">{childrenFn}</Id>);
+
+        // Assert
+        expect(childrenFn).toHaveBeenCalledWith("my-id");
+    });
+});
diff --git a/packages/wonder-blocks-core/src/components/id.tsx b/packages/wonder-blocks-core/src/components/id.tsx
@@ -0,0 +1,34 @@
+import {useId} from "react";
+import * as React from "react";
+
+type Props = {
+    /**
+     * An identifier to use.
+     *
+     * If this is omitted, an identifier is generated.
+     */
+    id?: string | undefined;
+
+    /**
+     * A function that to render children with the given identifier.
+     */
+    children: (id: string) => React.ReactNode;
+};
+
+/**
+ * A component that provides an identifier to its children.
+ *
+ * If an `id` prop is provided, that is passed through to the children;
+ * otherwise, a unique identifier is generated.
+ */
+export const Id = ({id, children}: Props) => {
+    const generatedId = useId();
+
+    // If we already have an ID, then use that.
+    // Otherwise, use the generated ID.
+    // NOTE: We can't call hooks conditionally, but it should be pretty cheap
+    // to call useId() and not use the result, rather than the alternative
+    // which would be to have a separate component for cases where we need
+    // to call the hook and then render the component conditionally.
+    return <>{children(id ?? generatedId)}</>;
+};
diff --git a/packages/wonder-blocks-core/src/index.ts b/packages/wonder-blocks-core/src/index.ts
@@ -13,6 +13,7 @@ export {default as IDProvider} from "./components/id-provider";
 export {default as UniqueIDProvider} from "./components/unique-id-provider";
 export {default as addStyle} from "./util/add-style";
 export {default as Server} from "./util/server";
+export {Id} from "./components/id";
 export {
     useUniqueIdWithMock,
     useUniqueIdWithoutMock,