Merge env into $nu and simplify table/get (#1463)

crates/nu-protocol/src/lib.rs

@@ -23,4 +23,4 @@ pub use crate::value::evaluate::{Evaluate, EvaluateTrait, Scope};
 pub use crate::value::primitive::Primitive;
 pub use crate::value::primitive::{format_date, format_duration, format_primitive};
 pub use crate::value::range::{Range, RangeInclusion};
-pub use crate::value::{UntaggedValue, Value};
+pub use crate::value::{merge_descriptors, UntaggedValue, Value};

crates/nu-protocol/src/value.rs

@@ -378,3 +378,24 @@ impl From<ShellError> for UntaggedValue {
         UntaggedValue::Error(e)
     }
 }
+
+pub fn merge_descriptors(values: &[Value]) -> Vec<String> {
+    let mut ret: Vec<String> = vec![];
+    let value_column = "<value>".to_string();
+    for value in values {
+        let descs = value.data_descriptors();
+
+        if descs.is_empty() {
+            if !ret.contains(&value_column) {
+                ret.push("<value>".to_string());
+            }
+        } else {
+            for desc in value.data_descriptors() {
+                if !ret.contains(&desc) {
+                    ret.push(desc);
+                }
+            }
+        }
+    }
+    ret
+}