Make clear_var_list set nonexistant variables to empty strings
Make's clear-var-list causes the variables to exist as empty strings.
Mimic that functionality in starlark for the variable diff and ?=.
Bug: 262303006
Test: ./out/rbcrun ./build/make/tests/run.rbc
Change-Id: I5f9c8cf342d875b1022c5c74906e59fa68fcd6c9
diff --git a/tests/run.rbc b/tests/run.rbc
index 06f56d3..e8c4caa 100644
--- a/tests/run.rbc
+++ b/tests/run.rbc
@@ -164,13 +164,14 @@
g = {"FOO": "a", "BAR": "c", "BAZ": "e"}
cfg = {"FOO": "b", "BAR": "d", "BAZ": "f"}
-rblf.clear_var_list(g, struct(cfg=cfg), "FOO BAR")
+rblf.clear_var_list(g, struct(cfg=cfg), "FOO BAR NEWVAR")
assert_eq("", g["FOO"])
assert_eq("", cfg["FOO"])
assert_eq("", g["BAR"])
assert_eq("", cfg["BAR"])
assert_eq("e", g["BAZ"])
assert_eq("f", cfg["BAZ"])
+assert_eq("", g.get("NEWVAR"))
test_single_value_inheritance()
test_artifact_path_requirements()