Fix column count to not break on empty tables (#2374)

crates/nu-cli/src/commands/count.rs

@@ -39,23 +39,26 @@ impl WholeStreamCommand for Count {
         let (CountArgs { column }, input) = args.process(&registry).await?;
         let rows: Vec<Value> = input.collect().await;
 
-        if column {
+        let count = if column {
-            if let UntaggedValue::Row(dict) = &rows[0].value {
+            if rows.is_empty() {
-                return Ok(OutputStream::one(
+                0
-                    UntaggedValue::int(dict.length()).into_value(tag),
-                ));
             } else {
-                return Err(ShellError::labeled_error(
+                match &rows[0].value {
-                    "Cannot obtain column count",
+                    UntaggedValue::Row(dictionary) => dictionary.length(),
-                    "cannot obtain column count",
+                    _ => {
-                    tag,
+                        return Err(ShellError::labeled_error(
-                ));
+                            "Cannot obtain column count",
+                            "cannot obtain column count",
+                            tag,
+                        ));
+                    }
+                }
             }
-        }
+        } else {
+            rows.len()
+        };
 
-        Ok(OutputStream::one(
+        Ok(OutputStream::one(UntaggedValue::int(count).into_value(tag)))
-            UntaggedValue::int(rows.len()).into_value(tag),
-        ))
     }
 
     fn examples(&self) -> Vec<Example> {

crates/nu-cli/tests/commands/count.rs

@@ -11,3 +11,15 @@ fn count_columns_in_cal_table() {
 
     assert_eq!(actual.out, "7");
 }
+
+#[test]
+fn count_columns_no_rows() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        echo [] | count -c
+        "#
+    ));
+
+    assert_eq!(actual.out, "0");
+}