From fd41fa31d5917310d8480a6979c1ed4e41ede3ac Mon Sep 17 00:00:00 2001
From: Darren Schroeder <343840+fdncred@users.noreply.github.com>
Date: Tue, 2 Feb 2021 00:23:12 -0600
Subject: [PATCH] add $nothing and tests (#2995)

---
 crates/nu-engine/src/evaluate/evaluator.rs    |  5 ++++
 crates/nu-engine/tests/evaluate/invocation.rs | 23 +++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/crates/nu-engine/src/evaluate/evaluator.rs b/crates/nu-engine/src/evaluate/evaluator.rs
index 9272f3974..930b2ea0a 100644
--- a/crates/nu-engine/src/evaluate/evaluator.rs
+++ b/crates/nu-engine/src/evaluate/evaluator.rs
@@ -253,6 +253,11 @@ fn evaluate_reference(name: &str, ctx: &EvaluationContext, tag: Tag) -> Result<V
             )),
         },
 
+        "$nothing" => Ok(Value {
+            value: UntaggedValue::nothing(),
+            tag,
+        }),
+
         x => match ctx.scope.get_var(x) {
             Some(v) => Ok(v),
             None => Err(ShellError::labeled_error(
diff --git a/crates/nu-engine/tests/evaluate/invocation.rs b/crates/nu-engine/tests/evaluate/invocation.rs
index cb695fd0c..705ddea2c 100644
--- a/crates/nu-engine/tests/evaluate/invocation.rs
+++ b/crates/nu-engine/tests/evaluate/invocation.rs
@@ -11,3 +11,26 @@ fn test_parse_invocation_with_range() {
     );
     assert_eq!(actual.out, "[1,2,3]")
 }
+
+#[test]
+fn create_nothing_in_table() {
+    let actual = nu!(
+        cwd: ".",
+        r#"
+        echo [[column]; [$nothing]] | to json
+        "#
+    );
+    assert_eq!(actual.out, "{\"column\":null}");
+}
+
+#[test]
+fn compare_to_nothing() {
+    let actual = nu!(
+        cwd: ".",
+        r#"
+        let f = $nothing
+        if $f == $nothing {echo $true} {echo $false}
+        "#
+    );
+    assert_eq!(actual.out, "true");
+}