Better representation in nested dataframes (#3875)

* better dataframe representation in nested df

* Error message correction

crates/nu-command/src/commands/filters/reverse.rs

@@ -37,7 +37,10 @@ impl WholeStreamCommand for Reverse {
     }
 }
 
+#[allow(clippy::needless_collect)]
 fn reverse(args: CommandArgs) -> Result<ActionStream, ShellError> {
+    // Clippy warning should be ignored
+    // This collect is needed to apply rev
     let input = args.input.collect::<Vec<_>>();
     Ok((input.into_iter().rev().map(ReturnSuccess::value)).into_action_stream())
 }

crates/nu-data/src/base/shape.rs

@@ -13,6 +13,9 @@ use std::hash::{Hash, Hasher};
 use std::path::PathBuf;
 use sys_locale::get_locale;
 
+#[cfg(feature = "dataframe")]
+use nu_protocol::dataframe::{FrameStruct, NuDataFrame};
+
 #[derive(Debug, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Deserialize, Serialize)]
 pub struct InlineRange {
     from: (InlineShape, RangeInclusion),
@@ -45,9 +48,11 @@ pub enum InlineShape {
     // TODO: Error type
     Error,
 
-    // TODO: Dataframe type
     #[cfg(feature = "dataframe")]
-    DataFrame,
+    DataFrame(String),
+
+    #[cfg(feature = "dataframe")]
+    FrameStruct(String),
 
     // Stream markers (used as bookend markers rather than actual values)
     BeginningOfStream,
@@ -123,6 +128,24 @@ impl InlineShape {
         InlineShape::Table(vec)
     }
 
+    #[cfg(feature = "dataframe")]
+    pub fn from_df(df: &NuDataFrame) -> InlineShape {
+        let msg = format!("{} rows {} cols", df.as_ref().height(), df.as_ref().width());
+
+        InlineShape::DataFrame(msg)
+    }
+
+    #[cfg(feature = "dataframe")]
+    pub fn from_frame_struct(s: &FrameStruct) -> InlineShape {
+        match s {
+            FrameStruct::GroupBy(groupby) => {
+                let msg = groupby.by().join(",");
+                let msg = format!("groupby {}", msg);
+                InlineShape::DataFrame(msg)
+            }
+        }
+    }
+
     pub fn from_value<'a>(value: impl Into<&'a UntaggedValue>) -> InlineShape {
         match value.into() {
             UntaggedValue::Primitive(p) => InlineShape::from_primitive(p),
@@ -131,7 +154,9 @@ impl InlineShape {
             UntaggedValue::Error(_) => InlineShape::Error,
             UntaggedValue::Block(_) => InlineShape::Block,
             #[cfg(feature = "dataframe")]
-            UntaggedValue::DataFrame(_) | UntaggedValue::FrameStruct(_) => InlineShape::DataFrame,
+            UntaggedValue::DataFrame(df) => InlineShape::from_df(df),
+            #[cfg(feature = "dataframe")]
+            UntaggedValue::FrameStruct(s) => InlineShape::from_frame_struct(s),
         }
     }
 
@@ -344,7 +369,16 @@ impl PrettyDebug for FormatInlineShape {
             InlineShape::Block => DbgDocBldr::opaque("block"),
             InlineShape::Error => DbgDocBldr::error("error"),
             #[cfg(feature = "dataframe")]
-            InlineShape::DataFrame => DbgDocBldr::error("dataframe_pretty_formatter"),
+            InlineShape::DataFrame(msg) => DbgDocBldr::delimit(
+                "[",
+                DbgDocBldr::kind("dataframe") + DbgDocBldr::space() + DbgDocBldr::primitive(msg),
+                "]",
+            )
+            .group(),
+            #[cfg(feature = "dataframe")]
+            InlineShape::FrameStruct(msg) => {
+                DbgDocBldr::delimit("[", DbgDocBldr::primitive(msg), "]").group()
+            }
             InlineShape::BeginningOfStream => DbgDocBldr::blank(),
             InlineShape::EndOfStream => DbgDocBldr::blank(),
         }

crates/nu-protocol/src/dataframe/nu_dataframe.rs

@@ -173,7 +173,8 @@ impl NuDataFrame {
                 UntaggedValue::Primitive(Primitive::Int(_))
                 | UntaggedValue::Primitive(Primitive::Decimal(_))
                 | UntaggedValue::Primitive(Primitive::String(_))
-                | UntaggedValue::Primitive(Primitive::Boolean(_)) => {
+                | UntaggedValue::Primitive(Primitive::Boolean(_))
+                | UntaggedValue::DataFrame(_) => {
                     let key = format!("{}", 0);
                     insert_value(value, key, &mut column_values)?
                 }
@@ -286,6 +287,27 @@ impl NuDataFrame {
         Ok(series.clone())
     }
 
+    pub fn get_value(&self, row: usize, span: Span) -> Result<Value, ShellError> {
+        let series = self.as_series(&Span::default())?;
+        let column = create_column(&series, row, row + 1)?;
+
+        if column.len() == 0 {
+            Err(ShellError::labeled_error_with_secondary(
+                "Not a valid row",
+                format!("No value found for index {}", row),
+                span,
+                format!("Note that the column size is {}", series.len()),
+                span,
+            ))
+        } else {
+            let value = column
+                .into_iter()
+                .next()
+                .expect("already checked there is a value");
+            Ok(value)
+        }
+    }
+
     // Print is made out a head and if the dataframe is too large, then a tail
     pub fn print(&self) -> Result<Vec<Value>, ShellError> {
         let df = &self.as_ref();

crates/nu-protocol/src/dataframe/nu_groupby.rs

@@ -23,6 +23,10 @@ impl NuGroupBy {
         }
     }
 
+    pub fn by(&self) -> &[String] {
+        &self.by
+    }
+
     pub fn try_from_stream<T>(input: &mut T, span: &Span) -> Result<NuGroupBy, ShellError>
     where
         T: Iterator<Item = Value>,

crates/nu-value-ext/src/lib.rs

@@ -214,11 +214,17 @@ pub fn get_data_by_member(value: &Value, name: &PathMember) -> Result<Value, She
                     Tag::new(value.anchor(), name.span),
                 ))
             }
-            _ => Err(ShellError::labeled_error(
+            UnspannedPathMember::Int(int) => {
-                "Integer as column",
+                if df.is_series() {
-                "Only string as column name",
+                    df.get_value(*int as usize, name.span)
-                &name.span,
+                } else {
-            )),
+                    Err(ShellError::labeled_error(
+                        "Column not found",
+                        "Column name not found in the dataframe",
+                        name.span,
+                    ))
+                }
+            }
         },
         other => Err(ShellError::type_error(
             "row or table",