expression evaluation: clean up truth values

For historic reasons, we considerd special strings as false values.
Drop that behavior in favor of a clean LISP-like semantics: everything
is true that is not empty.

2 files changed, 1 insertions, 15 deletions

diff --git a/src/buildtool/build_engine/expression/evaluator.cpp b/src/buildtool/build_engine/expression/evaluator.cpp
index e573bf36..a768f43c 100644
--- a/src/buildtool/build_engine/expression/evaluator.cpp
+++ b/src/buildtool/build_engine/expression/evaluator.cpp
@@ -29,7 +29,7 @@ auto ValueIsTrue(ExpressionPtr const& val) -> bool {
         return *val != number_t{0};
     }
     if (val->IsString()) {
-        return *val != ""s and *val != "0"s and *val != "NO"s;
+        return *val != ""s;
     }
     if (val->IsList()) {
         return not val->List().empty();
diff --git a/test/buildtool/build_engine/expression/expression.test.cpp b/test/buildtool/build_engine/expression/expression.test.cpp
index 89ab6e5e..8db88412 100644
--- a/test/buildtool/build_engine/expression/expression.test.cpp
+++ b/test/buildtool/build_engine/expression/expression.test.cpp
@@ -418,20 +418,6 @@ TEST_CASE("Expression Evaluation", "[expression]") {  // NOLINT
             REQUIRE(fail1);
             REQUIRE(fail1->IsString());
             CHECK(fail1 == Expression::FromJson(R"("failure")"_json));
-
-            expr = Replace(expr, "cond", "0"s);
-            REQUIRE(expr);
-            auto fail2 = expr.Evaluate(env, fcts);
-            REQUIRE(fail2);
-            REQUIRE(fail2->IsString());
-            CHECK(fail2 == Expression::FromJson(R"("failure")"_json));
-
-            expr = Replace(expr, "cond", "NO"s);
-            REQUIRE(expr);
-            auto fail3 = expr.Evaluate(env, fcts);
-            REQUIRE(fail3);
-            REQUIRE(fail3->IsString());
-            CHECK(fail3 == Expression::FromJson(R"("failure")"_json));
         }
 
         SECTION("List condition") {