Built-in expressions: add enumerate

Add a function transforming a list into a map. In this way, artifacts
collected positionally in a list can easily be realized as a stage
used for input to an action or output of a target.

1 files changed, 18 insertions, 0 deletions

diff --git a/test/buildtool/build_engine/expression/expression.test.cpp b/test/buildtool/build_engine/expression/expression.test.cpp
index cbc8c7bf..11ff7a43 100644
--- a/test/buildtool/build_engine/expression/expression.test.cpp
+++ b/test/buildtool/build_engine/expression/expression.test.cpp
@@ -890,6 +890,24 @@ TEST_CASE("Expression Evaluation", "[expression]") {  // NOLINT
         CHECK(result == Expression::FromJson(R"("esXcXape me XX")"_json));
     }
 
+    SECTION("enumerate expression") {
+        auto expr = Expression::FromJson(R"(
+          { "type": "enumerate"
+          , "$1": ["foo", "bar", "baz"]
+          }
+        )"_json);
+        REQUIRE(expr);
+
+        auto result = expr.Evaluate(env, fcts);
+        REQUIRE(result);
+        CHECK(result == Expression::FromJson(R"(
+          { "0": "foo"
+          , "1": "bar"
+          , "2": "baz"
+          }
+        )"_json));
+    }
+
     SECTION("keys expression") {
         auto expr = Expression::FromJson(R"(
             { "type": "keys"