Error out if output path already exists (#20)

src/packaged/__init__.py

@@ -37,6 +37,10 @@ def __init__(self, python_version: str) -> None:
         self.python_version = python_version
 
 
+class OutputPathExists(Exception):
+    """Raised when the output path already exists."""
+
+
 def create_package(
     source_directory: str | None,
     output_path: str,
@@ -46,6 +50,9 @@ def create_package(
     quiet: bool = False,
 ) -> None:
     """Create the makeself executable, with the startup script in it."""
+    if os.path.exists(output_path):
+        raise OutputPathExists
+
     if source_directory is None:
         source_directory = tempfile.mkdtemp()
 

src/packaged/cli.py

@@ -9,6 +9,7 @@
 
 from packaged import (
     DEFAULT_PYTHON_VERSION,
+    OutputPathExists,
     PythonNotAvailable,
     SourceDirectoryNotFound,
     create_package,
@@ -23,7 +24,7 @@
 
 def error(message: str) -> None:
     """Print error message"""
-    print(f"\033[1;31mError:\033[m {message}")
+    print(f"\033[1;31mError:\033[m {message}", file=sys.stderr)
 
 
 def cli(argv: list[str] | None = None) -> int:
@@ -91,5 +92,11 @@ def cli(argv: list[str] | None = None) -> int:
     except PythonNotAvailable as exc:
         error(f"Python {exc.python_version!r} is not available for download.")
         return 5
+    except OutputPathExists:
+        err_msg = f"output path {config.output_path!r} already exists"
+        if config.output_path == ".":
+            err_msg += "\nConsider giving a filename, like './myapp.bin'"
+        error(err_msg)
+        return 6
 
     return 0