From 6c1c7f95090649b3d73845f9cc81f35a3161161b Mon Sep 17 00:00:00 2001
From: Jack Wright <56345+ayax79@users.noreply.github.com>
Date: Fri, 6 Sep 2024 20:03:51 -0700
Subject: [PATCH] Added expression support for `polars cumulative` (#13799)

# Description
Provides the ability to use `polars cumulative` as an expression:

<img width="1266" alt="Screenshot 2024-09-06 at 17 47 15"
src="https://github.com/user-attachments/assets/73c11f79-598c-4efa-bfcd-755e536ead66">

# User-Facing Changes
- `polars cumulative` can now be used as an expression.
---
 .../command/aggregation/cumulative.rs         | 96 ++++++++++++++++---
 1 file changed, 83 insertions(+), 13 deletions(-)

diff --git a/crates/nu_plugin_polars/src/dataframe/command/aggregation/cumulative.rs b/crates/nu_plugin_polars/src/dataframe/command/aggregation/cumulative.rs
index e745bf5432..db3affbd25 100644
--- a/crates/nu_plugin_polars/src/dataframe/command/aggregation/cumulative.rs
+++ b/crates/nu_plugin_polars/src/dataframe/command/aggregation/cumulative.rs
@@ -1,6 +1,8 @@
 use crate::{values::CustomValueSupport, PolarsPlugin};
 
-use crate::values::{Column, NuDataFrame};
+use crate::values::{
+    cant_convert_err, Column, NuDataFrame, NuExpression, PolarsPluginObject, PolarsPluginType,
+};
 
 use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
 use nu_protocol::{
@@ -52,22 +54,53 @@ impl PluginCommand for Cumulative {
     }
 
     fn description(&self) -> &str {
-        "Cumulative calculation for a series."
+        "Cumulative calculation for a column or series."
     }
 
     fn signature(&self) -> Signature {
         Signature::build(self.name())
-            .required("type", SyntaxShape::String, "rolling operation")
-            .switch("reverse", "Reverse cumulative calculation", Some('r'))
-            .input_output_type(
-                Type::Custom("dataframe".into()),
-                Type::Custom("dataframe".into()),
+            .required(
+                "type",
+                SyntaxShape::String,
+                "rolling operation. Values of min, max, and sum are accepted.",
             )
+            .switch("reverse", "Reverse cumulative calculation", Some('r'))
+            .input_output_types(vec![
+                (
+                    Type::Custom("dataframe".into()),
+                    Type::Custom("dataframe".into()),
+                ),
+                (
+                    Type::Custom("expression".into()),
+                    Type::Custom("expression".into()),
+                ),
+            ])
             .category(Category::Custom("dataframe".into()))
     }
 
     fn examples(&self) -> Vec<Example> {
         vec![
+            Example {
+                description: "Cumulative sum for a column",
+                example: "[[a]; [1] [2] [3] [4] [5]] | polars into-df | polars select (polars col a | polars cumulative sum | polars as cum_a) | polars collect",
+                result: Some(
+                    NuDataFrame::try_from_columns(
+                        vec![Column::new(
+                            "cum_a".to_string(),
+                            vec![
+                                Value::test_int(1),
+                                Value::test_int(3),
+                                Value::test_int(6),
+                                Value::test_int(10),
+                                Value::test_int(15),
+                            ],
+                        )],
+                        None,
+                    )
+                    .expect("simple df for test should not fail")
+                    .into_value(Span::test_data()),
+                ),
+            },
             Example {
                 description: "Cumulative sum for a series",
                 example: "[1 2 3 4 5] | polars into-df | polars cumulative sum",
@@ -120,20 +153,58 @@ impl PluginCommand for Cumulative {
         call: &EvaluatedCall,
         input: PipelineData,
     ) -> Result<PipelineData, LabeledError> {
-        command(plugin, engine, call, input).map_err(LabeledError::from)
+        let value = input.into_value(call.head)?;
+        let cum_type: Spanned<String> = call.req(0)?;
+        let cum_type = CumulativeType::from_str(&cum_type.item, cum_type.span)?;
+        match PolarsPluginObject::try_from_value(plugin, &value)? {
+            PolarsPluginObject::NuDataFrame(df) => command_df(plugin, engine, call, cum_type, df),
+            PolarsPluginObject::NuLazyFrame(lazy) => {
+                command_df(plugin, engine, call, cum_type, lazy.collect(call.head)?)
+            }
+            PolarsPluginObject::NuExpression(expr) => {
+                command_expr(plugin, engine, call, cum_type, expr)
+            }
+            _ => Err(cant_convert_err(
+                &value,
+                &[
+                    PolarsPluginType::NuDataFrame,
+                    PolarsPluginType::NuLazyFrame,
+                    PolarsPluginType::NuExpression,
+                ],
+            )),
+        }
+        .map_err(LabeledError::from)
     }
 }
 
-fn command(
+fn command_expr(
     plugin: &PolarsPlugin,
     engine: &EngineInterface,
     call: &EvaluatedCall,
-    input: PipelineData,
+    cum_type: CumulativeType,
+    expr: NuExpression,
 ) -> Result<PipelineData, ShellError> {
-    let cum_type: Spanned<String> = call.req(0)?;
     let reverse = call.has_flag("reverse")?;
+    let polars = expr.into_polars();
 
-    let df = NuDataFrame::try_from_pipeline_coerce(plugin, input, call.head)?;
+    let res: NuExpression = match cum_type {
+        CumulativeType::Max => polars.cum_max(reverse),
+        CumulativeType::Min => polars.cum_min(reverse),
+        CumulativeType::Sum => polars.cum_sum(reverse),
+    }
+    .into();
+
+    res.to_pipeline_data(plugin, engine, call.head)
+}
+
+fn command_df(
+    plugin: &PolarsPlugin,
+    engine: &EngineInterface,
+    call: &EvaluatedCall,
+    cum_type: CumulativeType,
+    df: NuDataFrame,
+) -> Result<PipelineData, ShellError> {
+    let reverse = call.has_flag("reverse")?;
     let series = df.as_series(call.head)?;
 
     if let DataType::Object(..) = series.dtype() {
@@ -146,7 +217,6 @@ fn command(
         });
     }
 
-    let cum_type = CumulativeType::from_str(&cum_type.item, cum_type.span)?;
     let mut res = match cum_type {
         CumulativeType::Max => cum_max(&series, reverse),
         CumulativeType::Min => cum_min(&series, reverse),