Modify line reader to always consume stderr and mark stderr in callba…

…ck (#560)

This PR modifies the behavior of lineReader which would previously only
tried on reading from stderr when requested.

Since typically stderr is used to pass on important information and
given almost all uses in out codebase would set stderr as `true`, this
method now connects to stderr by default.

For the use-cases where we want to be able to tell whether line comes
from stderr or stdout (like with the sim-server stdout that is used as
communication and control channel), the line callback gets an additional
argument that indicates whether line comes from stderr.

## Test plan

Run expo-router, try clean rebuild on Android and iOS

packages/vscode-extension/src/builders/buildAndroid.ts

@@ -120,7 +120,7 @@ export async function buildAndroid(
   );
   const buildAndroidProgressProcessor = new BuildAndroidProgressProcessor(progressListener);
   outputChannel.clear();
-  lineReader(buildProcess, true).onLineRead((line) => {
+  lineReader(buildProcess).onLineRead((line) => {
     outputChannel.appendLine(line);
     buildAndroidProgressProcessor.processLine(line);
   });

packages/vscode-extension/src/builders/buildIOS.ts

@@ -126,7 +126,7 @@ export async function buildIos(
 
     const buildIOSProgressProcessor = new BuildIOSProgressProcessor(progressListener);
     outputChannel.clear();
-    lineReader(process, true).onLineRead((line) => {
+    lineReader(process).onLineRead((line) => {
       outputChannel.appendLine(line);
       buildIOSProgressProcessor.processLine(line);
       // Xcode can sometimes escape `=` with a backslash or put the value in quotes

packages/vscode-extension/src/devices/preview.ts

@@ -50,16 +50,21 @@ export class Preview implements Disposable {
 
       const streamURLRegex = /(http:\/\/[^ ]*stream\.mjpeg)/;
 
-      lineReader(subprocess).onLineRead((line) => {
+      lineReader(subprocess).onLineRead((line, stderr) => {
+        if (stderr) {
+          Logger.info("sim-server:", line);
+          return;
+        }
+
         const match = line.match(streamURLRegex);
 
         if (match) {
-          Logger.debug(`Preview server ready ${match[1]}`);
+          Logger.info(`Stream ready ${match[1]}`);
 
           this.streamURL = match[1];
           resolve(this.streamURL);
         }
-        Logger.debug("Preview server:", line);
+        Logger.info("sim-server:", line);
       });
     });
   }

packages/vscode-extension/src/project/metro.ts

@@ -191,7 +191,7 @@ export class Metro implements Disposable {
           reject(new Error("Metro exited but did not start server successfully."));
         });
 
-      lineReader(bundlerProcess, true).onLineRead((line) => {
+      lineReader(bundlerProcess).onLineRead((line) => {
         try {
           const event = JSON.parse(line) as MetroEvent;
           if (event.type === "bundle_transform_progressed") {

packages/vscode-extension/src/utilities/subprocess.ts

@@ -2,6 +2,7 @@ import { Logger } from "../Logger";
 import execa, { ExecaChildProcess } from "execa";
 import readline from "readline";
 import { Platform } from "./platform";
+import { inc } from "semver";
 
 export type ChildProcess = ExecaChildProcess<string>;
 
@@ -62,26 +63,25 @@ function overrideEnv<T extends execa.Options>(options?: T): T | undefined {
  * When using this methid, the subprocess should be started with buffer: false option
  * as there's no need for allocating memory for the output that's going to be very long.
  */
-export function lineReader(childProcess: ExecaChildProcess<string>, includeStderr = false) {
-  const input = childProcess.stdout;
-  if (!input) {
-    throw new Error("Child process has no stdout");
+export function lineReader(childProcess: ExecaChildProcess<string>) {
+  if (!childProcess.stdout) {
+    throw new Error("Child process doesn't have stdout");
   }
   const stdoutReader = readline.createInterface({
-    input,
+    input: childProcess.stdout,
     terminal: false,
   });
-  let stderrReader = null;
-  if (includeStderr && childProcess.stderr) {
+  let stderrReader: readline.Interface | null = null;
+  if (childProcess.stderr) {
     stderrReader = readline.createInterface({
-      input: childProcess.stderr!,
+      input: childProcess.stderr,
       terminal: false,
     });
   }
   return {
-    onLineRead: (callback: (line: string) => void) => {
+    onLineRead: (callback: (line: string, stderr?: boolean) => void) => {
       stdoutReader.on("line", callback);
-      stderrReader?.on("line", callback);
+      stderrReader?.on("line", (line) => callback(line, true));
     },
   };
 }