Raise exception if rotate pages threshold adjusted without --rotate-pages

Fixes Make usage of --rotate-pages-threshold clearer #1309

src/ocrmypdf/_defaults.py

@@ -0,0 +1,8 @@
+# SPDX-FileCopyrightText: 2024 James R. Barlow
+# SPDX-License-Identifier: MPL-2.0
+
+# Enforce English hegemony
+DEFAULT_LANGUAGE = 'eng'
+
+# Default rotation threshold
+DEFAULT_ROTATE_PAGES_THRESHOLD = 14.0

src/ocrmypdf/_validation.py

@@ -20,6 +20,7 @@ import pikepdf
 import PIL
 from pluggy import PluginManager
 
+from ocrmypdf._defaults import DEFAULT_LANGUAGE, DEFAULT_ROTATE_PAGES_THRESHOLD
 from ocrmypdf._exec import unpaper
 from ocrmypdf.exceptions import (
     BadArgsError,
@@ -30,17 +31,9 @@ from ocrmypdf.exceptions import (
 from ocrmypdf.helpers import is_file_writable, monotonic, safe_symlink
 from ocrmypdf.subprocess import check_external_program
 
-# -------------
-# External dependencies
-
-DEFAULT_LANGUAGE = 'eng'  # Enforce English hegemony
-
 log = logging.getLogger(__name__)
 
 
-# --------
-
-
 def check_platform() -> None:
     if sys.maxsize <= 2**32:  # pragma: no cover
         log.warning(
@@ -130,6 +123,11 @@ def check_options_preprocessing(options: Namespace) -> None:
         options.clean = True
     if options.unpaper_args and not options.clean:
         raise BadArgsError("--clean is required for --unpaper-args")
+    if (
+        options.rotate_pages_threshold != DEFAULT_ROTATE_PAGES_THRESHOLD
+        and not options.rotate_pages
+    ):
+        raise BadArgsError("--rotate-pages is required for --rotate-pages-threshold")
     if options.clean:
         check_external_program(
             program='unpaper',

src/ocrmypdf/cli.py

@@ -9,6 +9,7 @@ import argparse
 from collections.abc import Callable, Mapping
 from typing import Any, TypeVar
 
+from ocrmypdf._defaults import DEFAULT_ROTATE_PAGES_THRESHOLD
 from ocrmypdf._version import PROGRAM_NAME as _PROGRAM_NAME
 from ocrmypdf._version import __version__ as _VERSION
 
@@ -403,7 +404,7 @@ Online documentation is located at:
     )
     advanced.add_argument(
         '--rotate-pages-threshold',
-        default=14.0,
+        default=DEFAULT_ROTATE_PAGES_THRESHOLD,
         type=numeric(float, 0, 1000),
         metavar='CONFIDENCE',
         help="Only rotate pages when confidence is above this value (arbitrary "