dataframe list command (#4681)

crates/nu-command/src/dataframe/eager/list.rs

@@ -0,0 +1,102 @@
+use nu_protocol::{
+    ast::Call,
+    engine::{Command, EngineState, Stack},
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Value,
+};
+
+use crate::dataframe::values::NuDataFrame;
+
+#[derive(Clone)]
+pub struct ListDF;
+
+impl Command for ListDF {
+    fn name(&self) -> &str {
+        "dfr list"
+    }
+
+    fn usage(&self) -> &str {
+        "Lists stored dataframes"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build(self.name()).category(Category::Custom("dataframe".into()))
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Creates a new dataframe and shows it in the dataframe list",
+            example: r#"let test = ([[a b];[1 2] [3 4]] | dfr to-df);
+    dfr list"#,
+            result: None,
+        }]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        _input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let vals = engine_state
+            .scope
+            .iter()
+            .flat_map(|frame| {
+                frame
+                    .vars
+                    .iter()
+                    .filter_map(|var| {
+                        let value = stack.get_var(*var.1, call.head);
+                        match value {
+                            Ok(value) => {
+                                let name = String::from_utf8_lossy(var.0).to_string();
+                                Some((name, value))
+                            }
+                            Err(_) => None,
+                        }
+                    })
+                    .collect::<Vec<(String, Value)>>()
+            })
+            .filter_map(|(name, value)| match NuDataFrame::try_from_value(value) {
+                Ok(df) => Some((name, df)),
+                Err(_) => None,
+            })
+            .map(|(name, df)| {
+                let name = Value::String {
+                    val: name,
+                    span: call.head,
+                };
+
+                let columns = Value::Int {
+                    val: df.as_ref().width() as i64,
+                    span: call.head,
+                };
+
+                let rows = Value::Int {
+                    val: df.as_ref().height() as i64,
+                    span: call.head,
+                };
+
+                let cols = vec![
+                    "name".to_string(),
+                    "columns".to_string(),
+                    "rows".to_string(),
+                ];
+                let vals = vec![name, columns, rows];
+
+                Value::Record {
+                    cols,
+                    vals,
+                    span: call.head,
+                }
+            })
+            .collect::<Vec<Value>>();
+
+        let list = Value::List {
+            vals,
+            span: call.head,
+        };
+
+        Ok(list.into_pipeline_data())
+    }
+}

crates/nu-command/src/dataframe/eager/mod.rs

@@ -14,6 +14,7 @@ mod get;
 mod groupby;
 mod join;
 mod last;
+mod list;
 mod melt;
 mod open;
 mod pivot;
@@ -47,6 +48,7 @@ pub use get::GetDF;
 pub use groupby::CreateGroupBy;
 pub use join::JoinDF;
 pub use last::LastDF;
+pub use list::ListDF;
 pub use melt::MeltDF;
 pub use open::OpenDataFrame;
 pub use pivot::PivotDF;
@@ -90,6 +92,7 @@ pub fn add_eager_decls(working_set: &mut StateWorkingSet) {
         GetDF,
         JoinDF,
         LastDF,
+        ListDF,
         MeltDF,
         OpenDataFrame,
         PivotDF,