Fix single value inheritance

Single-value product variables resolve to the first
instance of that variable in prefix order. What we
have right now is taking the value from the current
makefile if it's set, but if it's not, we take it
from the last child, not the first.

Fixes: 226206409
Test: Manually
Change-Id: Id23f7c269ff9a352bf0b67cb57156b72449f978e

core/product_config.rbc

@@ -291,7 +291,10 @@ def _percolate_inherited(configs, cfg_name, cfg, children_names):
         child_cfg = configs[child_name][1]
         for attr, value in child_cfg.items():
             if type(value) != "list":
-                if attr in percolated_attrs or not attr in cfg:
+                # Single value variables take the first value available from the leftmost
+                # branch of the tree. If we also had "or attr in percolated_attrs" in this
+                # if statement, it would take the value from the rightmost branch.
+                if cfg.get(attr, "") == "":
                     cfg[attr] = value
                     percolated_attrs[attr] = True
                 continue

tests/run.rbc

@@ -25,6 +25,7 @@ load(":input_variables.rbc", input_variables_init = "init")
 load(":product.rbc", "init")
 load(":board.rbc", board_init = "init")
 load(":board_input_vars.rbc", board_input_vars_init = "init")
+load("//build/make/tests/single_value_inheritance:test.rbc", test_single_value_inheritance = "test")
 
 def assert_eq(expected, actual):
     if expected != actual:
@@ -129,3 +130,5 @@ assert_eq(
 (board_globals, board_config, board_globals_base) = rblf.board_configuration(board_init, board_input_vars_init)
 assert_eq({"A_LIST_VARIABLE": ["foo", "bar"]}, board_globals)
 assert_eq({"A_LIST_VARIABLE": ["foo"]}, board_globals_base)
+
+test_single_value_inheritance()

tests/single_value_inheritance/inherit1.rbc

@@ -0,0 +1,21 @@
+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("//build/make/core:product_config.rbc", "rblf")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+
+  cfg["PRODUCT_CHARACTERISTICS"] = "tablet"
+  cfg["PRODUCT_DEFAULT_DEV_CERTIFICATE"] = "vendor/myvendor/certs/devkeys/devkey"

tests/single_value_inheritance/inherit2.rbc

@@ -0,0 +1,20 @@
+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("//build/make/core:product_config.rbc", "rblf")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+
+  cfg["PRODUCT_CHARACTERISTICS"] = "nosdcard"

tests/single_value_inheritance/product.rbc

@@ -0,0 +1,24 @@
+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("//build/make/core:product_config.rbc", "rblf")
+load(":inherit1.rbc", _inherit1_init = "init")
+load(":inherit2.rbc", _inherit2_init = "init")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  rblf.inherit(handle, "test/inherit1", _inherit1_init)
+  rblf.inherit(handle, "test/inherit2", _inherit2_init)
+
+  cfg["PRODUCT_DEFAULT_DEV_CERTIFICATE"] = ""

tests/single_value_inheritance/test.rbc

@@ -0,0 +1,27 @@
+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("//build/make/core:product_config.rbc", "rblf")
+load("//build/make/tests/input_variables.rbc", input_variables_init = "init")
+load(":product.rbc", "init")
+
+
+def assert_eq(expected, actual):
+    if expected != actual:
+        fail("Expected '%s', got '%s'" % (expected, actual))
+
+def test():
+    (globals, config, globals_base) = rblf.product_configuration("test/device", init, input_variables_init)
+    assert_eq("tablet", config["PRODUCT_CHARACTERISTICS"])
+    assert_eq("vendor/myvendor/certs/devkeys/devkey", config["PRODUCT_DEFAULT_DEV_CERTIFICATE"])