generate_*_tests.py --directory: fix handling of relative path

The option to --directory was intended to be relative to the current
directory when the script is invoked, which is the intuitive behavior. But
this was not implemented correctly, and it was actually interpreted relative
to the mbedtls root (which the script chdir's into). Fix this.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

scripts/mbedtls_dev/test_data_generation.py

@@ -141,8 +141,7 @@ class BaseTarget(metaclass=ABCMeta):
 class TestGenerator:
     """Generate test cases and write to data files."""
     def __init__(self, options) -> None:
-        self.test_suite_directory = self.get_option(options, 'directory',
-                                                    'tests/suites')
+        self.test_suite_directory = options.directory
         # Update `targets` with an entry for each child class of BaseTarget.
         # Each entry represents a file generated by the BaseTarget framework,
         # and enables generating the .data files using the CLI.
@@ -151,11 +150,6 @@ class TestGenerator:
             for subclass in BaseTarget.__subclasses__()
         })
 
-    @staticmethod
-    def get_option(options, name: str, default: T) -> T:
-        value = getattr(options, name, None)
-        return default if value is None else value
-
     def filename_for(self, basename: str) -> str:
         """The location of the data file with the specified base name."""
         return posixpath.join(self.test_suite_directory, basename + '.data')
@@ -189,16 +183,24 @@ def main(args, description: str, generator_class: Type[TestGenerator] = TestGene
                         help='List available targets and exit')
     parser.add_argument('--list-for-cmake', action='store_true',
                         help='Print \';\'-separated list of available targets and exit')
+    # If specified explicitly, this option may be a path relative to the
+    # current directory when the script is invoked. The default value
+    # is relative to the mbedtls root, which we don't know yet. So we
+    # can't set a string as the default value here.
     parser.add_argument('--directory', metavar='DIR',
                         help='Output directory (default: tests/suites)')
-    # The `--directory` option is interpreted relative to the directory from
-    # which the script is invoked, but the default is relative to the root of
-    # the mbedtls tree. The default should not be set above, but instead after
-    # `build_tree.chdir_to_root()` is called.
     parser.add_argument('targets', nargs='*', metavar='TARGET',
                         help='Target file to generate (default: all; "-": none)')
     options = parser.parse_args(args)
+
+    # Change to the mbedtls root, to keep things simple. But first, adjust
+    # command line options that might be relative paths.
+    if options.directory is None:
+        options.directory = 'tests/suites'
+    else:
+        options.directory = os.path.abspath(options.directory)
     build_tree.chdir_to_root()
+
     generator = generator_class(options)
     if options.list:
         for name in sorted(generator.targets):