use execFile() instead of spawn() to simplify logic

Author: matthewbastien

lldb/tools/lldb-dap/src-ts/process-tree/base-process-tree.ts

@@ -1,6 +1,8 @@
-import { ChildProcessWithoutNullStreams } from "child_process";
+import * as util from "util";
+import * as child_process from "child_process";
 import { Process, ProcessTree } from ".";
-import { Transform } from "stream";
+
+const exec = util.promisify(child_process.execFile);
 
 /** Parses process information from a given line of process output. */
 export type ProcessTreeParser = (line: string) => Process | undefined;
@@ -10,93 +12,30 @@ export type ProcessTreeParser = (line: string) => Process | undefined;
  */
 export abstract class BaseProcessTree implements ProcessTree {
   /**
-   * Spawn the process responsible for collecting all processes on the system.
+   * Get the command responsible for collecting all processes on the system.
    */
-  protected abstract spawnProcess(): ChildProcessWithoutNullStreams;
+  protected abstract getCommand(): string;
+
+  /**
+   * Get the list of arguments used to launch the command.
+   */
+  protected abstract getCommandArguments(): string[];
 
   /**
    * Create a new parser that can read the process information from stdout of the process
    * spawned by {@link spawnProcess spawnProcess()}.
    */
   protected abstract createParser(): ProcessTreeParser;
 
-  listAllProcesses(): Promise<Process[]> {
-    return new Promise<Process[]>((resolve, reject) => {
-      const proc = this.spawnProcess();
-      const parser = this.createParser();
-
-      // Capture processes from stdout
-      const processes: Process[] = [];
-      proc.stdout.pipe(new LineBasedStream()).on("data", (line) => {
-        const process = parser(line.toString());
-        if (process && process.id !== proc.pid) {
-          processes.push(process);
-        }
-      });
-
-      // Resolve or reject the promise based on exit code/signal/error
-      proc.on("error", reject);
-      proc.on("exit", (code, signal) => {
-        if (code === 0) {
-          resolve(processes);
-        } else if (signal) {
-          reject(
-            new Error(
-              `Unable to list processes: process exited due to signal ${signal}`,
-            ),
-          );
-        } else {
-          reject(
-            new Error(
-              `Unable to list processes: process exited with code ${code}`,
-            ),
-          );
-        }
-      });
-    });
-  }
-}
-
-/**
- * A stream that emits each line as a single chunk of data. The end of a line is denoted
- * by the newline character '\n'.
- */
-export class LineBasedStream extends Transform {
-  private readonly newline: number = "\n".charCodeAt(0);
-  private buffer: Buffer = Buffer.alloc(0);
-
-  override _transform(
-    chunk: Buffer,
-    _encoding: string,
-    callback: () => void,
-  ): void {
-    let currentIndex = 0;
-    while (currentIndex < chunk.length) {
-      const newlineIndex = chunk.indexOf(this.newline, currentIndex);
-      if (newlineIndex === -1) {
-        this.buffer = Buffer.concat([
-          this.buffer,
-          chunk.subarray(currentIndex),
-        ]);
-        break;
+  async listAllProcesses(): Promise<Process[]> {
+    const execCommand = exec(this.getCommand(), this.getCommandArguments());
+    const parser = this.createParser();
+    return (await execCommand).stdout.split("\n").flatMap((line) => {
+      const process = parser(line.toString());
+      if (!process || process.id === execCommand.child.pid) {
+        return [];
       }
-
-      const newlineChunk = chunk.subarray(currentIndex, newlineIndex);
-      const line = Buffer.concat([this.buffer, newlineChunk]);
-      this.push(line);
-      this.buffer = Buffer.alloc(0);
-
-      currentIndex = newlineIndex + 1;
-    }
-
-    callback();
-  }
-
-  override _flush(callback: () => void): void {
-    if (this.buffer.length) {
-      this.push(this.buffer);
-    }
-
-    callback();
+      return [process];
+    });
   }
 }

lldb/tools/lldb-dap/src-ts/process-tree/platforms/darwin-process-tree.ts

@@ -1,16 +1,15 @@
-import { ChildProcessWithoutNullStreams, spawn } from "child_process";
 import { LinuxProcessTree } from "./linux-process-tree";
 
 function fill(prefix: string, suffix: string, length: number): string {
   return prefix + suffix.repeat(length - prefix.length);
 }
 
 export class DarwinProcessTree extends LinuxProcessTree {
-  protected override spawnProcess(): ChildProcessWithoutNullStreams {
-    return spawn("ps", [
+  protected override getCommandArguments(): string[] {
+    return [
       "-xo",
       // The length of comm must be large enough or data will be truncated.
       `pid=PID,lstart=START,comm=${fill("COMMAND", "-", 256)},command=ARGUMENTS`,
-    ]);
+    ];
   }
 }

lldb/tools/lldb-dap/src-ts/process-tree/platforms/linux-process-tree.ts

@@ -1,15 +1,12 @@
-import { ChildProcessWithoutNullStreams, spawn } from "child_process";
 import { BaseProcessTree, ProcessTreeParser } from "../base-process-tree";
 
 export class LinuxProcessTree extends BaseProcessTree {
-  protected override spawnProcess(): ChildProcessWithoutNullStreams {
-    return spawn(
-      "ps",
-      ["-axo", `pid=PID,lstart=START,comm:128=COMMAND,command=ARGUMENTS`],
-      {
-        stdio: "pipe",
-      },
-    );
+  protected override getCommand(): string {
+    return "ps";
+  }
+
+  protected override getCommandArguments(): string[] {
+    return ["-axo", "pid=PID,lstart=START,comm:128=COMMAND,command=ARGUMENTS"];
   }
 
   protected override createParser(): ProcessTreeParser {

lldb/tools/lldb-dap/src-ts/process-tree/platforms/windows-process-tree.ts

@@ -1,20 +1,18 @@
 import * as path from "path";
 import { BaseProcessTree, ProcessTreeParser } from "../base-process-tree";
-import { ChildProcessWithoutNullStreams, spawn } from "child_process";
 
 export class WindowsProcessTree extends BaseProcessTree {
-  protected override spawnProcess(): ChildProcessWithoutNullStreams {
-    const wmic = path.join(
+  protected override getCommand(): string {
+    return path.join(
       process.env["WINDIR"] || "C:\\Windows",
       "System32",
       "wbem",
       "WMIC.exe",
     );
-    return spawn(
-      wmic,
-      ["process", "get", "CommandLine,CreationDate,ProcessId"],
-      { stdio: "pipe" },
-    );
+  }
+
+  protected override getCommandArguments(): string[] {
+    return ["process", "get", "CommandLine,CreationDate,ProcessId"];
   }
 
   protected override createParser(): ProcessTreeParser {