runners: tests: fix os.path.isfile patch

Copy a fix from test_nrfjprog.py to the other runner test suites. The
current code will enter an infinite recursion if you hit the path
where os.path.isfile is called, since it's been patched to
os_path_isfile_patch in the calling context. The fix is to cache the
'real' version in the parent scope and call it directly as a fallback.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>

scripts/west_commands/tests/test_bossac.py

@@ -161,11 +161,12 @@ def bcfg_check_cond5(item):
 def bcfg_get_cond5(item):
     return dict(BC_DICT_COND5)[item]
 
+os_path_isfile = os.path.isfile
+
 def os_path_isfile_patch(filename):
     if filename == RC_KERNEL_BIN:
         return True
-    return os.path.isfile(filename)
-
+    return os_path_isfile(filename)
 
 @patch('runners.bossac.BossacBinaryRunner.supports',
 	return_value=False)

scripts/west_commands/tests/test_canopen_program.py

@@ -30,10 +30,12 @@ TEST_CASES = [(n, x, p, c, o, t)
               for o in (False, True)
               for t in range(1, 3)]
 
+os_path_isfile = os.path.isfile
+
 def os_path_isfile_patch(filename):
     if filename == RC_KERNEL_BIN:
         return True
-    return os.path.isfile(filename)
+    return os_path_isfile(filename)
 
 @pytest.mark.parametrize('test_case', TEST_CASES)
 @patch('runners.canopen_program.CANopenProgramDownloader')

scripts/west_commands/tests/test_dfu_util.py

@@ -55,10 +55,12 @@ def find_device_patch():
 def require_patch(program):
     assert program in [DFU_UTIL, TEST_EXE]
 
+os_path_isfile = os.path.isfile
+
 def os_path_isfile_patch(filename):
     if filename == RC_KERNEL_BIN:
         return True
-    return os.path.isfile(filename)
+    return os_path_isfile(filename)
 
 def id_fn(tc):
     return 'exe={},alt={},dfuse_config={},img={}'.format(*tc)

scripts/west_commands/tests/test_stm32flash.py

@@ -65,10 +65,12 @@ def os_path_getsize_patch(filename):
         return TEST_BIN_SIZE
     return os.path.isfile(filename)
 
+os_path_isfile = os.path.isfile
+
 def os_path_isfile_patch(filename):
     if filename == RC_KERNEL_BIN:
         return True
-    return os.path.isfile(filename)
+    return os_path_isfile(filename)
 
 @pytest.mark.parametrize('action', EXPECTED_COMMANDS)
 @patch('runners.core.ZephyrBinaryRunner.require', side_effect=require_patch)