Function validatePythonPath

src/python/pythonUtils.ts:234–289

(pythonPath: string, isExplicit: boolean)

 * @throws {Error} If no valid Python executable is found.
 */
export async function validatePythonPath(pythonPath: string, isExplicit: boolean): Promise<string> {
  // Return cached result if available
  if (state.cachedPythonPath) {
    return state.cachedPythonPath;
  }

  // Create validation promise atomically if it doesn't exist
  // This prevents race conditions where multiple calls create separate validations
  if (!state.validationPromise) {
    state.validationPromise = (async () => {
      try {
        const primaryPath = await tryPath(pythonPath);
        if (primaryPath) {
          state.cachedPythonPath = primaryPath;
          state.validationPromise = null;
          return primaryPath;
        }

        if (isExplicit) {
          const error = new Error(
            `Python 3 not found. Tried "${pythonPath}" ` +
              `Please ensure Python 3 is installed and set the PROMPTFOO_PYTHON environment variable ` +
              `to your Python 3 executable path (e.g., '${process.platform === 'win32' ? 'C:\\Python39\\python.exe' : '/usr/bin/python3'}').`,
          );
          // Clear promise on error to allow retry
          state.validationPromise = null;
          throw error;
        }

        // Try to get Python executable using comprehensive detection
        const detectedPath = await getSysExecutable();
        if (detectedPath) {
          state.cachedPythonPath = detectedPath;
          state.validationPromise = null;
          return detectedPath;
        }

        const error = new Error(
          `Python 3 not found. Tried "${pythonPath}", sys.executable detection, and fallback commands. ` +
            `Please ensure Python 3 is installed and set the PROMPTFOO_PYTHON environment variable ` +
            `to your Python 3 executable path (e.g., '${process.platform === 'win32' ? 'C:\\Python39\\python.exe' : '/usr/bin/python3'}').`,
        );
        // Clear promise on error to allow retry
        state.validationPromise = null;
        throw error;
      } catch (error) {
        // Ensure promise is cleared on any error
        state.validationPromise = null;
        throw error;
      }
    })();
  }

  // Return the existing or newly-created promise
  return state.validationPromise;
}

/**