From f29dbeddd7d9040898d10b892badd8fc39db0967 Mon Sep 17 00:00:00 2001
From: JT <547158+jntrnr@users.noreply.github.com>
Date: Fri, 4 Feb 2022 16:19:13 -0500
Subject: [PATCH] Allow let-env to be dynamic (#940)

---
 crates/nu-command/src/env/let_env.rs | 6 ++----
 src/tests/test_engine.rs             | 5 +++++
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/crates/nu-command/src/env/let_env.rs b/crates/nu-command/src/env/let_env.rs
index 829abf1cc1..4035959cca 100644
--- a/crates/nu-command/src/env/let_env.rs
+++ b/crates/nu-command/src/env/let_env.rs
@@ -1,4 +1,4 @@
-use nu_engine::{current_dir, eval_expression_with_input};
+use nu_engine::{current_dir, eval_expression_with_input, CallExt};
 use nu_protocol::ast::Call;
 use nu_protocol::engine::{Command, EngineState, Stack};
 use nu_protocol::{Category, PipelineData, Signature, SyntaxShape, Value};
@@ -33,9 +33,7 @@ impl Command for LetEnv {
         call: &Call,
         input: PipelineData,
     ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
-        let env_var = call.positional[0]
-            .as_string()
-            .expect("internal error: missing variable");
+        let env_var = call.req(engine_state, stack, 0)?;
 
         let keyword_expr = call.positional[1]
             .as_keyword()
diff --git a/src/tests/test_engine.rs b/src/tests/test_engine.rs
index aae132b880..eb38281600 100644
--- a/src/tests/test_engine.rs
+++ b/src/tests/test_engine.rs
@@ -230,3 +230,8 @@ fn export_def_env() -> TestResult {
         "BAZ",
     )
 }
+
+#[test]
+fn dynamic_let_env() -> TestResult {
+    run_test(r#"let x = "FOO"; let-env $x = "BAZ"; $env.FOO"#, "BAZ")
+}