zenflow/composite-service

import { spawn } from "child_process";
import { resolve, normalize } from "path";
import npmRunPath from "npm-run-path";
import which from "which";
import { NormalizedServiceConfig } from "./validateAndNormalizeConfig";

// Match the isWindows definition from `node-which`
// https://github.com/npm/node-which/blob/6a822d836de79f92fb3170f685a6e283fbfeff87/which.js#L1-L3
const isWindows =
  process.platform === "win32" || process.env.OSTYPE === "cygwin" || process.env.OSTYPE === "msys";

export function spawnProcess(config: NormalizedServiceConfig) {
  const cwd = resolve(config.cwd);
  let [binary, ...args] = config.command;
  let env = { ...config.env };

  let path = readEnvCaseInsensitive(env, "PATH") || "";
  path = filterBlankParts(npmRunPath({ cwd, path }));
  env = writeEnvCaseNormalized(env, "PATH", path);

  if (isWindows) {
    const pathExt =
      readEnvCaseInsensitive(env, "PATHEXT") || ".COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH";
    env = writeEnvCaseNormalized(env, "PATHEXT", pathExt);
    /*
      Work around issue (same issue):
        - https://github.com/nodejs/node-v0.x-archive/issues/2318
        - https://github.com/nodejs/node/issues/6671

      Without resorting to wrapping command in shell (like npm package `cross-spawn` does)
      because [spawning a shell is expensive](https://github.com/nodejs/node/issues/6671#issuecomment-219210529)
      and more importantly, that approach introduces *more* window-linux disparities.

      Instead just replace `binary` with a fully-qualified version.
     */
    binary = normalize(myWhich(cwd, binary, path, pathExt) || binary);
  }

  return spawn(binary, args, { cwd, env });
}

function readEnvCaseInsensitive(env: { [key: string]: string }, key: string): string | undefined {
  const upperCaseKey = key.toUpperCase();
  const caseInsensitiveKey = Object.keys(env)
    .reverse()
    .find((key) => key.toUpperCase() === upperCaseKey);
  return caseInsensitiveKey === undefined ? undefined : env[caseInsensitiveKey];
}

function writeEnvCaseNormalized(
  env: { [key: string]: string },
  key: string,
  value: string
): { [key: string]: string } {
  const upperCaseKey = key.toUpperCase();
  return {
    ...Object.fromEntries(
      Object.entries(env).filter(([key]) => key.toUpperCase() !== upperCaseKey)
    ),
    [upperCaseKey]: value,
  };
}

function filterBlankParts(string: string) {
  const colon = isWindows ? ";" : ":";
  return string.split(colon).filter(Boolean).join(colon);
}

// Version of `which.sync` that adds a `cwd` parameter & doesn't throw
function myWhich(cwd: string, binary: string, path: string, pathExt: string) {
  const originalCwd = process.cwd();
  if (cwd !== originalCwd) {
    process.chdir(cwd);
  }
  const result = which.sync(binary, { nothrow: true, path, pathExt });
  if (cwd !== originalCwd) {
    process.chdir(originalCwd);
  }
  return result;
}