Improve CDP Flow types

packages/dev-middleware/src/inspector-proxy/Device.js

@@ -11,15 +11,11 @@
 
 import type {EventReporter} from '../types/EventReporter';
 import type {
-  DebuggerRequest,
-  ErrorResponse,
-  GetScriptSourceRequest,
-  GetScriptSourceResponse,
-  MessageFromDevice,
-  MessageToDevice,
-  Page,
-  SetBreakpointByUrlRequest,
-} from './types';
+  CDPClientMessage,
+  CDPRequest,
+  CDPResponse,
+} from './cdp-types/messages';
+import type {MessageFromDevice, MessageToDevice, Page} from './types';
 
 import DeviceEventReporter from './DeviceEventReporter';
 import * as fs from 'fs';
@@ -581,27 +577,32 @@ export default class Device {
     }
   }
 
-  // Allows to make changes in incoming messages from debugger. Returns a boolean
-  // indicating whether the message has been handled locally (i.e. does not need
-  // to be forwarded to the target).
+  /**
+   * Intercept an incoming message from a connected debugger. Returns either an
+   * original/replacement CDP message object, or `null` (will forward nothing
+   * to the target).
+   */
   #interceptMessageFromDebuggerLegacy(
-    req: DebuggerRequest,
+    req: CDPClientMessage,
     debuggerInfo: DebuggerInfo,
     socket: WS,
-  ): ?DebuggerRequest {
-    if (req.method === 'Debugger.setBreakpointByUrl') {
-      return this.#processDebuggerSetBreakpointByUrl(req, debuggerInfo);
-    } else if (req.method === 'Debugger.getScriptSource') {
-      this.#processDebuggerGetScriptSource(req, socket);
-      return null;
+  ): CDPClientMessage | null {
+    switch (req.method) {
+      case 'Debugger.setBreakpointByUrl':
+        return this.#processDebuggerSetBreakpointByUrl(req, debuggerInfo);
+      case 'Debugger.getScriptSource':
+        // Sends response to debugger via side-effect
+        this.#processDebuggerGetScriptSource(req, socket);
+        return null;
+      default:
+        return req;
     }
-    return req;
   }
 
   #processDebuggerSetBreakpointByUrl(
-    req: SetBreakpointByUrlRequest,
+    req: CDPRequest<'Debugger.setBreakpointByUrl'>,
     debuggerInfo: DebuggerInfo,
-  ): SetBreakpointByUrlRequest {
+  ): CDPRequest<'Debugger.setBreakpointByUrl'> {
     // If we replaced Android emulator's address to localhost we need to change it back.
     if (debuggerInfo.originalSourceURLAddress != null) {
       const processedReq = {...req, params: {...req.params}};
@@ -635,10 +636,16 @@ export default class Device {
     return req;
   }
 
-  #processDebuggerGetScriptSource(req: GetScriptSourceRequest, socket: WS) {
+  #processDebuggerGetScriptSource(
+    req: CDPRequest<'Debugger.getScriptSource'>,
+    socket: WS,
+  ): void {
     const sendSuccessResponse = (scriptSource: string) => {
-      const result: GetScriptSourceResponse = {scriptSource};
-      const response = {id: req.id, result};
+      const result = {scriptSource};
+      const response: CDPResponse<'Debugger.getScriptSource'> = {
+        id: req.id,
+        result,
+      };
       socket.send(JSON.stringify(response));
       this.#deviceEventReporter?.logResponse(response, 'proxy', {
         pageId: this.#debuggerConnection?.pageId ?? null,
@@ -647,7 +654,7 @@ export default class Device {
     };
     const sendErrorResponse = (error: string) => {
       // Tell the client that the request failed
-      const result: ErrorResponse = {error: {message: error}};
+      const result = {error: {message: error}};
       const response = {id: req.id, result};
       socket.send(JSON.stringify(response));
 

packages/dev-middleware/src/inspector-proxy/DeviceEventReporter.js

@@ -9,6 +9,7 @@
  */
 
 import type {EventReporter} from '../types/EventReporter';
+import type {CDPResponse} from './cdp-types/messages';
 
 import TTLCache from '@isaacs/ttlcache';
 
@@ -69,11 +70,7 @@ class DeviceEventReporter {
   }
 
   logResponse(
-    res: $ReadOnly<{
-      id: number,
-      error?: {message: string, data?: mixed},
-      ...
-    }>,
+    res: CDPResponse<>,
     origin: 'device' | 'proxy',
     metadata: $ReadOnly<{
       pageId: string | null,

packages/dev-middleware/src/inspector-proxy/cdp-types/messages.js

@@ -0,0 +1,45 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ * @oncall react_native
+ */
+
+import type {Commands, Events} from './protocol';
+
+// Note: A CDP event is a JSON-RPC notification with no `id` member.
+export type CDPEvent<TEvent: $Keys<Events> = 'unknown'> = $ReadOnly<{
+  method: TEvent,
+  params: Events[TEvent],
+}>;
+
+export type CDPRequest<TCommand: $Keys<Commands> = 'unknown'> = $ReadOnly<{
+  method: TCommand,
+  params: Commands[TCommand]['paramsType'],
+  id: number,
+}>;
+
+export type CDPResponse<TCommand: $Keys<Commands> = 'unknown'> =
+  | $ReadOnly<{
+      result: Commands[TCommand]['resultType'],
+      id: number,
+    }>
+  | $ReadOnly<{
+      error: CDPRequestError,
+      id: number,
+    }>;
+
+export type CDPRequestError = $ReadOnly<{
+  code: number,
+  message: string,
+  data?: mixed,
+}>;
+
+export type CDPClientMessage =
+  | CDPRequest<'Debugger.getScriptSource'>
+  | CDPRequest<'Debugger.setBreakpointByUrl'>
+  | CDPRequest<>;

packages/dev-middleware/src/inspector-proxy/cdp-types/protocol.js

@@ -0,0 +1,88 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ * @oncall react_native
+ */
+
+// Adapted from https://github.com/ChromeDevTools/devtools-protocol/blob/master/types/protocol.d.ts
+
+export interface Debugger {
+  GetScriptSourceParams: $ReadOnly<{
+    /**
+     * Id of the script to get source for.
+     */
+    scriptId: string,
+  }>;
+
+  GetScriptSourceResult: $ReadOnly<{
+    /**
+     * Script source (empty in case of Wasm bytecode).
+     */
+    scriptSource: string,
+
+    /**
+     * Wasm bytecode. (Encoded as a base64 string when passed over JSON)
+     */
+    bytecode?: string,
+  }>;
+
+  SetBreakpointByUrlParams: $ReadOnly<{
+    /**
+     * Line number to set breakpoint at.
+     */
+    lineNumber: number,
+
+    /**
+     * URL of the resources to set breakpoint on.
+     */
+    url?: string,
+
+    /**
+     * Regex pattern for the URLs of the resources to set breakpoints on. Either `url` or
+     * `urlRegex` must be specified.
+     */
+    urlRegex?: string,
+
+    /**
+     * Script hash of the resources to set breakpoint on.
+     */
+    scriptHash?: string,
+
+    /**
+     * Offset in the line to set breakpoint at.
+     */
+    columnNumber?: number,
+
+    /**
+     * Expression to use as a breakpoint condition. When specified, debugger will only stop on the
+     * breakpoint if this expression evaluates to true.
+     */
+    condition?: string,
+  }>;
+}
+
+export type Events = {
+  [method: string]: mixed,
+};
+
+export type Commands = {
+  'Debugger.getScriptSource': {
+    paramsType: Debugger['GetScriptSourceParams'],
+    resultType: Debugger['GetScriptSourceResult'],
+  },
+
+  'Debugger.setBreakpointByUrl': {
+    paramsType: Debugger['SetBreakpointByUrlParams'],
+    resultType: void,
+  },
+
+  [method: string]: {
+    paramsType: mixed,
+    resultType: mixed,
+  },
+};

packages/dev-middleware/src/inspector-proxy/types.js

@@ -95,49 +95,6 @@ export type JsonVersionResponse = $ReadOnly<{
   'Protocol-Version': string,
 }>;
 
-/**
- * Types were exported from https://github.com/ChromeDevTools/devtools-protocol/blob/master/types/protocol.d.ts
- */
-
-export type SetBreakpointByUrlRequest = $ReadOnly<{
-  id: number,
-  method: 'Debugger.setBreakpointByUrl',
-  params: $ReadOnly<{
-    lineNumber: number,
-    url?: string,
-    urlRegex?: string,
-    scriptHash?: string,
-    columnNumber?: number,
-    condition?: string,
-  }>,
-}>;
-
-export type GetScriptSourceRequest = $ReadOnly<{
-  id: number,
-  method: 'Debugger.getScriptSource',
-  params: {
-    scriptId: string,
-  },
-}>;
-
-export type GetScriptSourceResponse = $ReadOnly<{
-  scriptSource: string,
-  /**
-   * Wasm bytecode.
-   */
-  bytecode?: string,
-}>;
-
-export type ErrorResponse = $ReadOnly<{
-  error: $ReadOnly<{
-    message: string,
-  }>,
-}>;
-
-export type DebuggerRequest =
-  | SetBreakpointByUrlRequest
-  | GetScriptSourceRequest;
-
 export type JSONSerializable =
   | boolean
   | number