Add code to update the shadow file

Add code to compare the shadow file containing the list of config options
with the options in the config file. Also add code to update (or just
create) the shadow file.

Signed-off-by: Gilles Peskine <[email protected]>

scripts/mbedtls_framework/config_macros.py

@@ -76,18 +76,74 @@ class Current(ConfigMacros):
         """The path to the option list shadow file."""
         return os.path.join(self._root, self._submodule, self._SHADOW_FILE)
 
-    def __init__(self, submodule: str = '') -> None:
+    def __init__(self, submodule: str = '',
+                 shadow_missing_ok: bool = False) -> None:
         """Look for macros defined in the given submodule's source tree.
 
         If submodule is omitted or empty, look in the root module.
+
+        If shadow_missing_ok is true, treat a missing shadow file as
+        if it was empty. This is intended for use only when regenerating
+        the shadow file.
         """
         self._root = build_tree.guess_project_root()
         self._submodule = submodule
         shadow_file = self.shadow_file_path()
-        public = self._load_file(shadow_file)
+        try:
+            public = self._load_file(shadow_file)
+        except FileNotFoundError:
+            if not shadow_missing_ok:
+                raise
+            public = frozenset()
         adjusted = self._search_files(self._ADJUST_CONFIG_HEADERS)
         super().__init__(public, adjusted)
 
+    def live_config_options(self) -> FrozenSet[str]:
+        """Return config options from the config file (as opposed to the shadow file)."""
+        return self._search_files(self._PUBLIC_CONFIG_HEADERS)
+
+    def compare_shadow_file(self) -> Iterator[str]:
+        """Compare the option list shadow file with the live config file.
+
+        Yield the names that are only found in one of them, in a diff-like
+        format: prefixed by ``+`` if the name is missing from the shadow file,
+        or by ``-`` if the name is only in the shadow file.
+        """
+        live = self.live_config_options()
+        for x in sorted(live | self._public):
+            if x not in live:
+                yield '+' + x
+            elif x not in self._public:
+                yield '-' + x
+
+    def compare_shadow_file_verbosely(self) -> bool:
+        """Compare the shadow file with the live config file. Print differences.
+
+        Return True if they have the same data, False otherwise.
+        """
+        same = True
+        for line in self.compare_shadow_file():
+            same = False
+            print(line)
+        return same
+
+    def update_shadow_file(self, always_update: bool) -> None:
+        """Update the shadow file from the live config file.
+
+        If always_update is false and the shadow file already has the desired
+        content, don't touch it.
+        """
+        if not always_update:
+            try:
+                next(self.compare_shadow_file())
+            except StopIteration:
+                # The file is already up-to-date. Don't touch it.
+                return
+        with open(self.shadow_file_path(), 'w') as out:
+            for name in sorted(self.live_config_options()):
+                out.write(name + '\n')
+
+
 
 class History(ConfigMacros):
     """Information about config-like macros in a previous version.