Create Io interface and refactor fs-specific code into NativeIo

src/commandRunner.ts

@@ -1,18 +1,16 @@
-import { open } from "fs/promises";
 import { Minimatch } from "minimatch";
 import * as vscode from "vscode";
 
-import { readRequest, writeResponse } from "./io";
-import { getResponsePath } from "./paths";
 import { any } from "./regex";
 import { Request } from "./types";
+import { Io } from "./io";
 
 export default class CommandRunner {
-  allowRegex!: RegExp;
-  denyRegex!: RegExp | null;
-  backgroundWindowProtection!: boolean;
+  private allowRegex!: RegExp;
+  private denyRegex!: RegExp | null;
+  private backgroundWindowProtection!: boolean;
 
-  constructor() {
+  constructor(private io: Io) {
     this.reloadConfiguration = this.reloadConfiguration.bind(this);
     this.runCommand = this.runCommand.bind(this);
 
@@ -51,14 +49,14 @@ export default class CommandRunner {
    * types.
    */
   async runCommand() {
-    const responseFile = await open(getResponsePath(), "wx");
+    await this.io.prepareResponse();
 
     let request: Request;
 
     try {
-      request = await readRequest();
+      request = await this.io.readRequest();
     } catch (err) {
-      await responseFile.close();
+      await this.io.closeResponse();
       throw err;
     }
 
@@ -94,20 +92,20 @@ export default class CommandRunner {
         await commandPromise;
       }
 
-      await writeResponse(responseFile, {
+      await this.io.writeResponse({
         error: null,
         uuid,
         returnValue: commandReturnValue,
         warnings,
       });
     } catch (err) {
-      await writeResponse(responseFile, {
+      await this.io.writeResponse({
         error: (err as Error).message,
         uuid,
         warnings,
       });
     }
 
-    await responseFile.close();
+    await this.io.closeResponse();
   }
 }

src/extension.ts

@@ -1,14 +1,14 @@
 import * as vscode from "vscode";
 
+import { NativeIo } from "./nativeIo";
 import CommandRunner from "./commandRunner";
-import { initializeCommunicationDir } from "./initializeCommunicationDir";
-import { getInboundSignal } from "./signal";
 import { FocusedElementType } from "./types";
 
-export function activate(context: vscode.ExtensionContext) {
-  initializeCommunicationDir();
+export async function activate(context: vscode.ExtensionContext) {
+  const io = new NativeIo();
+  await io.initialize();
 
-  const commandRunner = new CommandRunner();
+  const commandRunner = new CommandRunner(io);
   let focusedElementType: FocusedElementType | undefined;
 
   context.subscriptions.push(
@@ -40,7 +40,7 @@ export function activate(context: vscode.ExtensionContext) {
        * This signal is emitted by the voice engine to indicate that a phrase has
        * just begun execution.
        */
-      prePhrase: getInboundSignal("prePhrase"),
+      prePhrase: io.getInboundSignal("prePhrase"),
     },
   };
 }

src/io.ts

@@ -1,36 +1,29 @@
-import { FileHandle, readFile, stat } from "fs/promises";
-import { VSCODE_COMMAND_TIMEOUT_MS } from "./constants";
-import { getRequestPath } from "./paths";
 import { Request, Response } from "./types";
-import { writeJSON } from "./fileUtils";
 
-/**
- * Reads the JSON-encoded request from the request file, unlinking the file
- * after reading.
- * @returns A promise that resolves to a Response object
- */
-export async function readRequest(): Promise<Request> {
-  const requestPath = getRequestPath();
-
-  const stats = await stat(requestPath);
-  const request = JSON.parse(await readFile(requestPath, "utf-8"));
-
-  if (
-    Math.abs(stats.mtimeMs - new Date().getTime()) > VSCODE_COMMAND_TIMEOUT_MS
-  ) {
-    throw new Error(
-      "Request file is older than timeout; refusing to execute command"
-    );
-  }
-
-  return request;
+export interface SignalReader {
+  /**
+   * Gets the current version of the signal. This version string changes every
+   * time the signal is emitted, and can be used to detect whether signal has
+   * been emitted between two timepoints.
+   * @returns The current signal version or null if the signal file could not be
+   * found
+   */
+  getVersion: () => Promise<string | null>;
 }
 
-/**
- * Writes the response to the response file as JSON.
- * @param file The file to write to
- * @param response The response object to JSON-encode and write to disk
- */
-export async function writeResponse(file: FileHandle, response: Response) {
-  await writeJSON(file, response);
+export interface Io {
+  initialize: () => Promise<void>;
+  // Prepares to send a response to readRequest, preventing any other process
+  // from doing so until closeResponse is called.  Throws an error if called
+  // twice before closeResponse.
+  prepareResponse: () => Promise<void>;
+  // Closes a prepared response, allowing other processes to respond to
+  // readRequest. Throws an error if the prepareResponse has not been called.
+  closeResponse: () => Promise<void>;
+  // Returns a request from Talon command client.
+  readRequest: () => Promise<Request>;
+  // Writes a response. Throws an error if prepareResponse has not been called.
+  writeResponse: (response: Response) => Promise<void>;
+  // Returns a SignalReader.
+  getInboundSignal: (name: string) => SignalReader;
 }

src/nativeIo.ts

@@ -0,0 +1,123 @@
+import { mkdirSync, lstatSync } from "fs";
+import { join } from "path";
+import { S_IWOTH } from "constants";
+import {
+  getCommunicationDirPath,
+  getRequestPath,
+  getResponsePath,
+  getSignalDirPath,
+} from "./paths";
+import { userInfo } from "os";
+import { Io } from "./io";
+import { FileHandle, open, readFile, stat } from "fs/promises";
+import { VSCODE_COMMAND_TIMEOUT_MS } from "./constants";
+import { Request, Response } from "./types";
+
+class InboundSignal {
+  constructor(private path: string) {}
+
+  /**
+   * Gets the current version of the signal. This version string changes every
+   * time the signal is emitted, and can be used to detect whether signal has
+   * been emitted between two timepoints.
+   * @returns The current signal version or null if the signal file could not be
+   * found
+   */
+  async getVersion() {
+    try {
+      return (await stat(this.path)).mtimeMs.toString();
+    } catch (err) {
+      if ((err as NodeJS.ErrnoException).code !== "ENOENT") {
+        throw err;
+      }
+
+      return null;
+    }
+  }
+}
+
+export class NativeIo implements Io {
+  private responseFile: FileHandle | null;
+
+  constructor() {
+    this.responseFile = null;
+  }
+
+  async initialize(): Promise<void> {
+    const communicationDirPath = getCommunicationDirPath();
+
+    console.debug(`Creating communication dir ${communicationDirPath}`);
+    mkdirSync(communicationDirPath, { recursive: true, mode: 0o770 });
+
+    const stats = lstatSync(communicationDirPath);
+
+    const info = userInfo();
+
+    if (
+      !stats.isDirectory() ||
+      stats.isSymbolicLink() ||
+      stats.mode & S_IWOTH ||
+      // On Windows, uid < 0, so we don't worry about it for simplicity
+      (info.uid >= 0 && stats.uid !== info.uid)
+    ) {
+      throw new Error(
+        `Refusing to proceed because of invalid communication dir ${communicationDirPath}`
+      );
+    }
+  }
+
+  async prepareResponse(): Promise<void> {
+    if (this.responseFile) {
+      throw new Error("response is already locked");
+    }
+    this.responseFile = await open(getResponsePath(), "wx");
+  }
+
+  async closeResponse(): Promise<void> {
+    if (!this.responseFile) {
+      throw new Error("response is not locked");
+    }
+    await this.responseFile.close();
+    this.responseFile = null;
+  }
+
+  /**
+   * Reads the JSON-encoded request from the request file, unlinking the file
+   * after reading.
+   * @returns A promise that resolves to a Response object
+   */
+  async readRequest(): Promise<Request> {
+    const requestPath = getRequestPath();
+
+    const stats = await stat(requestPath);
+    const request = JSON.parse(await readFile(requestPath, "utf-8"));
+
+    if (
+      Math.abs(stats.mtimeMs - new Date().getTime()) > VSCODE_COMMAND_TIMEOUT_MS
+    ) {
+      throw new Error(
+        "Request file is older than timeout; refusing to execute command"
+      );
+    }
+
+    return request;
+  }
+
+  /**
+   * Writes the response to the response file as JSON.
+   * @param file The file to write to
+   * @param response The response object to JSON-encode and write to disk
+   */
+  async writeResponse(response: Response) {
+    if (!this.responseFile) {
+      throw new Error("response is not locked");
+    }
+    await this.responseFile.write(`${JSON.stringify(response)}\n`);
+  }
+
+  getInboundSignal(name: string) {
+    const signalDir = getSignalDirPath();
+    const path = join(signalDir, name);
+    return new InboundSignal(path);
+  }
+}