Updated python_command_example.js

examples/python_command_example.js

@@ -1,32 +1,168 @@
-const { run, runSync } = require('../index');
+/**
+ * examples/python_command_example.js
+ *
+ * Robust example that demonstrates how to execute a Python script (or a Python
+ * command) from Node.js in a safe, cross-platform and Promise-based way.
+ *
+ * Features:
+ *  - Detects python3 / python on the system
+ *  - Uses execFile to avoid shell injection and quoting problems
+ *  - Allows passing arguments and environment overrides (useful for virtualenv)
+ *  - Optional timeout (ms)
+ *  - Programmatic API + CLI usage example
+ *
+ * Usage (CLI):
+ *   node examples/python_command_example.js path/to/script.py arg1 arg2
+ *
+ * Example (programmatic):
+ *   const { runPython } = require('./examples/python_command_example');
+ *   runPython('path/to/script.py', ['a','b'], { timeout: 10_000 })
+ *     .then(res => console.log(res.stdout))
+ *     .catch(err => console.error(err));
+ */
 
-const pythonVersionCmd = 'python --version';  // or 'python3 --version' if needed
-const pythonCommand = 'python -c "print(\'Hello from Python\')"';
+const { promisify } = require('util');
+const { execFile } = require('child_process');
+const fs = require('fs');
+const path = require('path');
 
-// Async example: print Python version, then run Python command
-(async () => {
+const execFileAsync = promisify(execFile);
+
+/**
+ * Try to pick a sensible Python binary name on the current system.
+ * Prefer 'python3' if available; fall back to 'python'.
+ *
+ * @returns {string} - The python command to use
+ */
+async function detectPythonBinary() {
+  const candidates = ['python3', 'python'];
+  for (const cmd of candidates) {
     try {
-        const { stdout: versionStdout } = await run(pythonVersionCmd);
-        console.log('Async Python Version:', versionStdout.trim());
+      // On many systems `--version` writes to stdout or stderr; we just check exit code.
+      await execFileAsync(cmd, ['--version'], { timeout: 2000 });
+      return cmd;
+    } catch (err) {
+      // ignore and try next candidate
+    }
+  }
+  // If neither command found, throw a helpful error.
+  throw new Error('No python binary found on PATH. Install Python or provide pythonPath option.');
+}
+
+/**
+ * Run a python script or module in a safe manner.
+ *
+ * @param {string} scriptPathOrModule - Path to a Python script (file) or module (pass "-m modulename" via options)
+ * @param {string[]} args - args to pass to the python invocation (argv for the script)
+ * @param {Object} options - optional
+ *     { string } pythonPath - override detected python binary
+ *     { number } timeout - ms, default 30000
+ *     { Object } env - extra env vars (merged with process.env)
+ *     { boolean } module - if true, run with -m <scriptPathOrModule> instead of file path
+ *
+ * @returns {Promise<{ stdout: string, stderr: string, exitCode: number }>}
+ */
+async function runPython(scriptPathOrModule, args = [], options = {}) {
+  const {
+    pythonPath = null,
+    timeout = 30_000,
+    env = {},
+    module = false,
+  } = options;
+
+  const pythonBinary = pythonPath || await detectPythonBinary();
+
+  const execArgs = [];
+  if (module) {
+    execArgs.push('-m', scriptPathOrModule);
+  } else {
+    // if it's a relative path, try to resolve it
+    const resolved = path.resolve(scriptPathOrModule);
+    if (!fs.existsSync(resolved)) {
+      throw new Error(`Python script not found at path: ${resolved}`);
+    }
+    execArgs.push(resolved);
+  }
 
-        const { stdout: commandStdout } = await run(pythonCommand);
-        console.log('Async Python Command Output:', commandStdout.trim());
-    } catch ({ err, stdout, stderr }) {
-        console.error('Async Python Error:', stderr || err);
+  // add the script args
+  if (Array.isArray(args) && args.length > 0) {
+    execArgs.push(...args.map(String));
+  }
+
+  const mergedEnv = Object.assign({}, process.env, env);
+
+  try {
+    const { stdout, stderr } = await execFileAsync(pythonBinary, execArgs, {
+      env: mergedEnv,
+      timeout,
+      maxBuffer: 10 * 1024 * 1024, // 10 MB stdout/stderr buffer
+    });
+    return {
+      stdout: stdout.toString(),
+      stderr: stderr.toString(),
+      exitCode: 0,
+    };
+  } catch (err) {
+    // err may be an Error with properties: code (exit code), stdout, stderr, signal, killed
+    // Normalize and rethrow a structured error so callers can handle it cleanly
+    const normalized = {
+      message: err.message,
+      exitCode: typeof err.code === 'number' ? err.code : null,
+      signal: err.signal || null,
+      stdout: (err.stdout || '').toString(),
+      stderr: (err.stderr || '').toString(),
+      timedOut: err.killed === true && err.signal === 'SIGTERM', // heuristic
+    };
+    const wrapper = new Error(`Python execution failed: ${normalized.message}`);
+    wrapper.details = normalized;
+    throw wrapper;
+  }
+}
+
+/**
+ * Minimal CLI wrapper so this example can be run standalone:
+ * node examples/python_command_example.js path/to/script.py arg1 arg2
+ */
+async function mainCli() {
+  const argv = process.argv.slice(2);
+  if (argv.length === 0) {
+    console.log('Usage: node examples/python_command_example.js <script.py | module> [args...]');
+    console.log('Example: node examples/python_command_example.js examples/hello.py Alice');
+    console.log('To run a module: set the env RUN_AS_MODULE=1 and pass the module name as first arg.');
+    process.exitCode = 1;
+    return;
+  }
+
+  const runAsModule = process.env.RUN_AS_MODULE === '1' || process.env.RUN_AS_MODULE === 'true';
+  const script = argv[0];
+  const args = argv.slice(1);
+
+  try {
+    const result = await runPython(script, args, {
+      timeout: 60_000,
+      module: runAsModule,
+    });
+    if (result.stdout) process.stdout.write(result.stdout);
+    if (result.stderr) process.stderr.write(result.stderr);
+    process.exitCode = 0;
+  } catch (e) {
+    console.error('Error running python:', e.message || e);
+    if (e.details) {
+      console.error('Exit code:', e.details.exitCode);
+      if (e.details.stdout) console.error('Stdout:', e.details.stdout);
+      if (e.details.stderr) console.error('Stderr:', e.details.stderr);
     }
-})();
-
-// Sync example: print Python version, then run Python command
-const versionResult = runSync(pythonVersionCmd);
-if (versionResult.error) {
-    console.error('Sync Python Version Error:', versionResult.stderr);
-} else {
-    console.log('Sync Python Version:', versionResult.stdout.trim());
+    process.exitCode = 2;
+  }
 }
 
-const commandResult = runSync(pythonCommand);
-if (commandResult.error) {
-    console.error('Sync Python Command Error:', commandResult.stderr);
-} else {
-    console.log('Sync Python Command Output:', commandResult.stdout.trim());
+// Export for other JS code to reuse
+module.exports = {
+  runPython,
+  detectPythonBinary,
+};
+
+// If called directly, run the CLI
+if (require.main === module) {
+  mainCli();
 }