[Flight] Add support BigInt support (#26479)

## Summary

Adds support for sending `BigInt` to Flight and Flight Reply

## How did you test this change?

- added tests

.eslintrc.js

@@ -449,6 +449,9 @@ module.exports = {
     $ReadOnlyArray: 'readonly',
     $Shape: 'readonly',
     AnimationFrameID: 'readonly',
+    // For Flow type annotation. Only `BigInt` is valid at runtime.
+    bigint: 'readonly',
+    BigInt: 'readonly',
     Class: 'readonly',
     ClientRect: 'readonly',
     CopyInspectedElementPath: 'readonly',

packages/react-client/src/ReactFlightClient.js

@@ -564,6 +564,10 @@ export function parseModelString(
         // Special encoding for `undefined` which can't be serialized as JSON otherwise.
         return undefined;
       }
+      case 'n': {
+        // BigInt
+        return BigInt(value.substring(2));
+      }
       default: {
         // We assume that anything else is a reference ID.
         const id = parseInt(value.substring(1), 16);

packages/react-client/src/ReactFlightReplyClient.js

@@ -75,6 +75,10 @@ function serializeUndefined(): string {
   return '$undefined';
 }
 
+function serializeBigInt(n: bigint): string {
+  return '$n' + n.toString(10);
+}
+
 function escapeStringValue(value: string): string {
   if (value[0] === '$') {
     // We need to escape $ prefixed strings since we use those to encode
@@ -264,9 +268,7 @@ export function processReply(
     }
 
     if (typeof value === 'bigint') {
-      throw new Error(
-        `BigInt (${value}) is not yet supported as an argument to a Server Function.`,
-      );
+      return serializeBigInt(value);
     }
 
     throw new Error(

packages/react-client/src/__tests__/ReactFlight-test.js

@@ -229,6 +229,25 @@ describe('ReactFlight', () => {
     expect(ReactNoop).toMatchRenderedOutput(null);
   });
 
+  it('can transport BigInt', async () => {
+    function ComponentClient({prop}) {
+      return `prop: ${prop} (${typeof prop})`;
+    }
+    const Component = clientReference(ComponentClient);
+
+    const model = <Component prop={90071992547409910000n} />;
+
+    const transport = ReactNoopFlightServer.render(model);
+
+    await act(async () => {
+      ReactNoop.render(await ReactNoopFlightClient.read(transport));
+    });
+
+    expect(ReactNoop).toMatchRenderedOutput(
+      'prop: 90071992547409910000 (bigint)',
+    );
+  });
+
   it('can render a lazy component as a shared component on the server', async () => {
     function SharedComponent({text}) {
       return (

packages/react-server-dom-webpack/src/__tests__/ReactFlightDOMReply-test.js

@@ -75,4 +75,11 @@ describe('ReactFlightDOMReply', () => {
     }
     expect(items).toEqual(['A', 'B', 'C']);
   });
+
+  it('can pass a BigInt as a reply', async () => {
+    const body = await ReactServerDOMClient.encodeReply(90071992547409910000n);
+    const n = await ReactServerDOMServer.decodeReply(body, webpackServerMap);
+
+    expect(n).toEqual(90071992547409910000n);
+  });
 });

packages/react-server/src/ReactFlightReplyServer.js

@@ -402,6 +402,10 @@ function parseModelString(
         // Special encoding for `undefined` which can't be serialized as JSON otherwise.
         return undefined;
       }
+      case 'n': {
+        // BigInt
+        return BigInt(value.substring(2));
+      }
       default: {
         // We assume that anything else is a reference ID.
         const id = parseInt(value.substring(1), 16);

packages/react-server/src/ReactFlightServer.js

@@ -553,6 +553,10 @@ function serializeUndefined(): string {
   return '$undefined';
 }
 
+function serializeBigInt(n: bigint): string {
+  return '$n' + n.toString(10);
+}
+
 function serializeClientReference(
   request: Request,
   parent:
@@ -931,10 +935,7 @@ export function resolveModelToJSON(
   }
 
   if (typeof value === 'bigint') {
-    throw new Error(
-      `BigInt (${value}) is not yet supported in Client Component props.` +
-        describeObjectForErrorMessage(parent, key),
-    );
+    return serializeBigInt(value);
   }
 
   throw new Error(

scripts/rollup/validate/eslintrc.esm.js

@@ -7,6 +7,7 @@ module.exports = {
   },
   globals: {
     // ES 6
+    BigInt: 'readonly',
     Map: 'readonly',
     Set: 'readonly',
     Proxy: 'readonly',

scripts/rollup/validate/eslintrc.fb.js

@@ -7,6 +7,7 @@ module.exports = {
   },
   globals: {
     // ES6
+    BigInt: 'readonly',
     Map: 'readonly',
     Set: 'readonly',
     Symbol: 'readonly',

scripts/rollup/validate/eslintrc.rn.js

@@ -7,6 +7,7 @@ module.exports = {
   },
   globals: {
     // ES6
+    BigInt: 'readonly',
     Map: 'readonly',
     Set: 'readonly',
     Symbol: 'readonly',

scripts/rollup/validate/eslintrc.umd.js

@@ -6,6 +6,7 @@ module.exports = {
   },
   globals: {
     // ES6
+    BigInt: 'readonly',
     Map: 'readonly',
     Set: 'readonly',
     Symbol: 'readonly',