Fixed an issue when extends does not override options in the right order // Resolve #4462

HISTORY.rst

@@ -23,6 +23,7 @@ PlatformIO Core 6
 * Removed dependency on the "zeroconf" package and install it only when a user lists mDNS devices (issue with zeroconf's LGPL license)
 * Show the real error message instead of "Can not remove temporary directory" when |PIOCONF| is broken (`issue #4480 <https://github.com/platformio/platformio-core/issues/4480>`_)
 * Fixed an issue with an incorrect test summary when a testcase name includes a colon (`issue #4508 <https://github.com/platformio/platformio-core/issues/4508>`_)
+* Fixed an issue when `extends <https://docs.platformio.org/en/latest/projectconf/sections/env/options/advanced/extends.html>`__ does not override options in the right order (`issue #4462 <https://github.com/platformio/platformio-core/issues/4462>`_)
 
 6.1.5 (2022-11-01)
 ~~~~~~~~~~~~~~~~~~

platformio/project/config.py

@@ -168,7 +168,7 @@ class ProjectConfigBase:
                 yield (section, option)
             if self._parser.has_option(section, "extends"):
                 extends_queue.extend(
-                    self.parse_multi_values(self._parser.get(section, "extends"))[::-1]
+                    self.parse_multi_values(self._parser.get(section, "extends"))
                 )
 
     def options(self, section=None, env=None):
@@ -249,7 +249,9 @@ class ProjectConfigBase:
         return None
 
     def _traverse_for_value(self, section, option, option_meta=None):
+        # print("_traverse_for_value", section, option)
         for _section, _option in self.walk_options(section):
+            # print(13, _section, _option)
             if _option == option or (
                 option_meta
                 and (

tests/project/test_config.py

@@ -205,9 +205,9 @@ def test_options(config):
     assert config.options(env="test_extends") == [
         "extends",
         "build_flags",
+        "monitor_speed",
         "lib_ldf_mode",
         "lib_compat_mode",
-        "monitor_speed",
         "custom_monitor_speed",
         "lib_deps",
         "lib_ignore",
@@ -245,9 +245,9 @@ def test_sysenv_options(config):
     assert config.options(env="test_extends") == [
         "extends",
         "build_flags",
+        "monitor_speed",
         "lib_ldf_mode",
         "lib_compat_mode",
-        "monitor_speed",
         "custom_monitor_speed",
         "lib_deps",
         "lib_ignore",
@@ -427,9 +427,9 @@ def test_items(config):
     assert config.items(env="test_extends") == [
         ("extends", ["strict_settings"]),
         ("build_flags", ["-D RELEASE"]),
+        ("monitor_speed", 115200),
         ("lib_ldf_mode", "chain+"),
         ("lib_compat_mode", "strict"),
-        ("monitor_speed", 115200),
         ("custom_monitor_speed", "115200"),
         ("lib_deps", ["Lib1", "Lib2"]),
         ("lib_ignore", ["LibIgnoreCustom"]),
@@ -647,3 +647,24 @@ test_testing_command =
     config = ProjectConfig(str(project_conf))
     testing_command = config.get("env:myenv", "test_testing_command")
     assert "$" not in " ".join(testing_command)
+
+
+def test_extends_order(tmp_path: Path):
+    project_conf = tmp_path / "platformio.ini"
+    project_conf.write_text(
+        """
+[a]
+board = test
+
+[b]
+upload_tool = two
+
+[c]
+upload_tool = three
+
+[env:native]
+extends = a, b, c
+    """
+    )
+    config = ProjectConfig(str(project_conf))
+    assert config.get("env:native", "upload_tool") == "three"