Fixing NuLazyFrame/NuDataFrame conversion issues (nushell#12538)

# Description

@maxim-uvarov brought up another case where converting back and forth
between eager and lazy dataframes was not working correctly:

```
> [[a b]; [6 2] [1 4] [4 1]] | polars into-lazy | polars append -c ([[a b]; [6 2] [1 4] [4 1]] | polars into-df)
Error: nu::shell::cant_convert

  × Can't convert to NuDataFrame.
   ╭─[entry nushell#1:1:49]
 1 │ [[a b]; [6 2] [1 4] [4 1]] | polars into-lazy | polars append -c ([[a b]; [6 2] [1 4] [4 1]] | polars into-df)
   ·                                                 ──────┬──────
   ·                                                       ╰── can't convert NuLazyFrameCustomValue to NuDataFrame
   ╰────
```

This pull request fixes this case and glaringly obvious similar cases I
could find.

Co-authored-by: Jack Wright <[email protected]>

crates/nu_plugin_polars/src/dataframe/eager/append.rs

@@ -126,7 +126,7 @@ fn command(
     };
 
     let df_other = NuDataFrame::try_from_value_coerce(plugin, &other, call.head)?;
-    let df = NuDataFrame::try_from_pipeline(plugin, input, call.head)?;
+    let df = NuDataFrame::try_from_pipeline_coerce(plugin, input, call.head)?;
     let df = df.append_df(&df_other, axis, call.head)?;
 
     df.to_pipeline_data(plugin, engine, call.head)

crates/nu_plugin_polars/src/dataframe/eager/first.rs

@@ -1,5 +1,5 @@
 use crate::{
-    values::{Column, CustomValueSupport},
+    values::{Column, CustomValueSupport, NuLazyFrame},
     PolarsPlugin,
 };
 
@@ -98,8 +98,8 @@ impl PluginCommand for FirstDF {
         input: PipelineData,
     ) -> Result<PipelineData, LabeledError> {
         let value = input.into_value(call.head);
-        if NuDataFrame::can_downcast(&value) {
-            let df = NuDataFrame::try_from_value(plugin, &value)?;
+        if NuDataFrame::can_downcast(&value) || NuLazyFrame::can_downcast(&value) {
+            let df = NuDataFrame::try_from_value_coerce(plugin, &value, call.head)?;
             command(plugin, engine, call, df).map_err(|e| e.into())
         } else {
             let expr = NuExpression::try_from_value(plugin, &value)?;

crates/nu_plugin_polars/src/dataframe/eager/get.rs

@@ -72,7 +72,7 @@ fn command(
     let columns: Vec<Value> = call.rest(0)?;
     let (col_string, col_span) = convert_columns_string(columns, call.head)?;
 
-    let df = NuDataFrame::try_from_pipeline(plugin, input, call.head)?;
+    let df = NuDataFrame::try_from_pipeline_coerce(plugin, input, call.head)?;
 
     let df = df
         .as_ref()

crates/nu_plugin_polars/src/dataframe/eager/last.rs

@@ -1,5 +1,5 @@
 use crate::{
-    values::{Column, CustomValueSupport},
+    values::{Column, CustomValueSupport, NuLazyFrame},
     PolarsPlugin,
 };
 
@@ -73,8 +73,8 @@ impl PluginCommand for LastDF {
         input: PipelineData,
     ) -> Result<PipelineData, LabeledError> {
         let value = input.into_value(call.head);
-        if NuDataFrame::can_downcast(&value) {
-            let df = NuDataFrame::try_from_value(plugin, &value)?;
+        if NuDataFrame::can_downcast(&value) || NuLazyFrame::can_downcast(&value) {
+            let df = NuDataFrame::try_from_value_coerce(plugin, &value, call.head)?;
             command(plugin, engine, call, df).map_err(|e| e.into())
         } else {
             let expr = NuExpression::try_from_value(plugin, &value)?;

crates/nu_plugin_polars/src/dataframe/eager/melt.rs

@@ -141,7 +141,7 @@ fn command(
     let (id_col_string, id_col_span) = convert_columns_string(id_col, call.head)?;
     let (val_col_string, val_col_span) = convert_columns_string(val_col, call.head)?;
 
-    let df = NuDataFrame::try_from_pipeline(plugin, input, call.head)?;
+    let df = NuDataFrame::try_from_pipeline_coerce(plugin, input, call.head)?;
 
     check_column_datatypes(df.as_ref(), &id_col_string, id_col_span)?;
     check_column_datatypes(df.as_ref(), &val_col_string, val_col_span)?;

crates/nu_plugin_polars/src/dataframe/eager/sample.rs

@@ -92,7 +92,7 @@ fn command(
     let replace: bool = call.has_flag("replace")?;
     let shuffle: bool = call.has_flag("shuffle")?;
 
-    let df = NuDataFrame::try_from_pipeline(plugin, input, call.head)?;
+    let df = NuDataFrame::try_from_pipeline_coerce(plugin, input, call.head)?;
 
     let df = match (rows, fraction) {
         (Some(rows), None) => df

crates/nu_plugin_polars/src/dataframe/eager/take.rs

@@ -101,7 +101,8 @@ fn command(
 ) -> Result<PipelineData, ShellError> {
     let index_value: Value = call.req(0)?;
     let index_span = index_value.span();
-    let index = NuDataFrame::try_from_value(plugin, &index_value)?.as_series(index_span)?;
+    let index = NuDataFrame::try_from_value_coerce(plugin, &index_value, call.head)?
+        .as_series(index_span)?;
 
     let casted = match index.dtype() {
         DataType::UInt32 | DataType::UInt64 | DataType::Int32 | DataType::Int64 => index

crates/nu_plugin_polars/src/dataframe/eager/to_nu.rs

@@ -4,7 +4,11 @@ use nu_protocol::{
     SyntaxShape, Type, Value,
 };
 
-use crate::{dataframe::values::NuExpression, values::CustomValueSupport, PolarsPlugin};
+use crate::{
+    dataframe::values::NuExpression,
+    values::{CustomValueSupport, NuLazyFrame},
+    PolarsPlugin,
+};
 
 use super::super::values::NuDataFrame;
 
@@ -86,7 +90,7 @@ impl PluginCommand for ToNu {
         input: PipelineData,
     ) -> Result<PipelineData, LabeledError> {
         let value = input.into_value(call.head);
-        if NuDataFrame::can_downcast(&value) {
+        if NuDataFrame::can_downcast(&value) || NuLazyFrame::can_downcast(&value) {
             dataframe_command(plugin, call, value)
         } else {
             expression_command(plugin, call, value)
@@ -103,7 +107,7 @@ fn dataframe_command(
     let rows: Option<usize> = call.get_flag("rows")?;
     let tail: bool = call.has_flag("tail")?;
 
-    let df = NuDataFrame::try_from_value(plugin, &input)?;
+    let df = NuDataFrame::try_from_value_coerce(plugin, &input, call.head)?;
 
     let values = if tail {
         df.tail(rows, call.head)?

crates/nu_plugin_polars/src/dataframe/eager/with_column.rs

@@ -145,7 +145,8 @@ fn command_eager(
         let df = lazy.collect(call.head)?;
         df.to_pipeline_data(plugin, engine, call.head)
     } else {
-        let mut other = NuDataFrame::try_from_value(plugin, &new_column)?.as_series(column_span)?;
+        let mut other = NuDataFrame::try_from_value_coerce(plugin, &new_column, call.head)?
+            .as_series(column_span)?;
 
         let name = match call.get_flag::<String>("name")? {
             Some(name) => name,

crates/nu_plugin_polars/src/dataframe/expressions/is_in.rs

@@ -165,7 +165,7 @@ fn command_df(
 ) -> Result<PipelineData, ShellError> {
     let other_value: Value = call.req(0)?;
     let other_span = other_value.span();
-    let other_df = NuDataFrame::try_from_value(plugin, &other_value)?;
+    let other_df = NuDataFrame::try_from_value_coerce(plugin, &other_value, call.head)?;
     let other = other_df.as_series(other_span)?;
     let series = df.as_series(call.head)?;
 
@@ -181,8 +181,9 @@ fn command_df(
 
     res.rename("is_in");
 
-    let df = NuDataFrame::try_from_series_vec(vec![res.into_series()], call.head)?;
-    df.to_pipeline_data(plugin, engine, call.head)
+    let mut new_df = NuDataFrame::try_from_series_vec(vec![res.into_series()], call.head)?;
+    new_df.from_lazy = df.from_lazy;
+    new_df.to_pipeline_data(plugin, engine, call.head)
 }
 
 #[cfg(test)]