polars: update polars lit to handle nushell Value::Duration and Value::Date types (#15564)

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# Description
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This PR seeks to expand `polars lit` to handle additional nushell types:
Value::Date and Value::Duration. This change is especially relevant to
the `polars filter` command, where expressions would then directly
incorporate Value::Date and Value::Duration types as literals. See one
such example below.

```nushell
#  Filter dataframe for rows where dt is within the last 2 days of the maximum dt value
  > [[dt val]; [2025-04-01 1] [2025-04-02 2] [2025-04-03 3] [2025-04-04 4]] | polars into-df | polars filter ((polars col dt) > ((polars col dt | polars max | $in - 2day)))
  ╭───┬─────────────────────┬─────╮
  │ # │          dt         │ val │
  ├───┼─────────────────────┼─────┤
  │ 0 │ 04/03/25 12:00:00AM │   3 │
  │ 1 │ 04/04/25 12:00:00AM │   4 │
  ╰───┴─────────────────────┴─────╯
```

# User-Facing Changes
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No breaking changes. Users now can directly access Value::Date and
Value::Duration types as literals in polars expressions.

# Tests + Formatting
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Several additional examples added to `polars lit` and `polars filter`

# After Submitting
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crates/nu_plugin_polars/src/dataframe/command/data/filter.rs

@@ -39,7 +39,8 @@ impl PluginCommand for LazyFilter {
     }
 
     fn examples(&self) -> Vec<Example> {
-        vec![Example {
+        vec![
+            Example {
                 description: "Filter dataframe using an expression",
                 example:
                     "[[a b]; [6 2] [4 2] [2 2]] | polars into-df | polars filter ((polars col a) >= 4)",
@@ -60,7 +61,47 @@ impl PluginCommand for LazyFilter {
                     .expect("simple df for test should not fail")
                     .into_value(Span::test_data()),
                 ),
-        }]
+            },
+            Example {
+                description: "Filter dataframe for rows where dt is within the last 2 days of the maximum dt value",
+                example:
+                    "[[dt val]; [2025-04-01 1] [2025-04-02 2] [2025-04-03 3] [2025-04-04 4]] | polars into-df | polars filter ((polars col dt) > ((polars col dt | polars max | $in - 2day)))",
+                result: Some(
+                NuDataFrame::try_from_columns(
+                    vec![
+                        Column::new(
+                            "dt".to_string(),
+                            vec![
+                                Value::date(
+                                    chrono::DateTime::parse_from_str(
+                                        "2025-04-03 00:00:00 +0000",
+                                        "%Y-%m-%d %H:%M:%S %z",
+                                    )
+                                    .expect("date calculation should not fail in test"),
+                                    Span::test_data(),
+                                ),
+                                Value::date(
+                                    chrono::DateTime::parse_from_str(
+                                        "2025-04-04 00:00:00 +0000",
+                                        "%Y-%m-%d %H:%M:%S %z",
+                                    )
+                                    .expect("date calculation should not fail in test"),
+                                    Span::test_data(),
+                                ),
+                            ]
+                        ),
+                        Column::new(
+                            "val".to_string(),
+                            vec![Value::test_int(3), Value::test_int(4)],
+                        ),
+                    ],
+                    None,
+                )
+                .expect("simple df for test should not fail")
+                .into_value(Span::test_data()),
+            ),
+        },
+    ]
     }
 
     fn run(

crates/nu_plugin_polars/src/dataframe/command/data/lit.rs

@@ -30,14 +30,40 @@ impl PluginCommand for ExprLit {
     }
 
     fn examples(&self) -> Vec<Example> {
-        vec![Example {
+        vec![
+            Example {
                 description: "Created a literal expression and converts it to a nu object",
                 example: "polars lit 2 | polars into-nu",
                 result: Some(Value::test_record(record! {
                     "expr" =>  Value::test_string("literal"),
                     "value" => Value::test_string("dyn int: 2"),
                 })),
-        }]
+            },
+            Example {
+                description: "Create a literal expression from date",
+                example: "polars lit 2025-04-13 | polars into-nu",
+                result: Some(Value::test_record(record! {
+                    "expr" => Value::test_record(record! {
+                        "expr" =>  Value::test_string("literal"),
+                        "value" => Value::test_string("dyn int: 1744502400000000000"),
+                    }),
+                    "dtype" => Value::test_string("Datetime(Nanoseconds, None)"),
+                    "cast_options" => Value::test_string("STRICT")
+                })),
+            },
+            Example {
+                description: "Create a literal expression from duration",
+                example: "polars lit 3hr | polars into-nu",
+                result: Some(Value::test_record(record! {
+                    "expr" => Value::test_record(record! {
+                        "expr" =>  Value::test_string("literal"),
+                        "value" => Value::test_string("dyn int: 10800000000000"),
+                    }),
+                    "dtype" => Value::test_string("Duration(Nanoseconds)"),
+                    "cast_options" => Value::test_string("STRICT")
+                })),
+            },
+        ]
     }
 
     fn search_terms(&self) -> Vec<&str> {

crates/nu_plugin_polars/src/dataframe/values/nu_expression/mod.rs

@@ -523,6 +523,32 @@ impl CustomValueSupport for NuExpression {
             Value::Int { val, .. } => Ok(val.to_owned().lit().into()),
             Value::Bool { val, .. } => Ok(val.to_owned().lit().into()),
             Value::Float { val, .. } => Ok(val.to_owned().lit().into()),
+            Value::Date { val, .. } => val
+                .to_owned()
+                .timestamp_nanos_opt()
+                .ok_or_else(|| ShellError::GenericError {
+                    error: "Integer overflow".into(),
+                    msg: "Provided datetime in nanoseconds is too large for i64".into(),
+                    span: Some(value.span()),
+                    help: None,
+                    inner: vec![],
+                })
+                .map(|nanos| -> NuExpression {
+                    nanos
+                        .lit()
+                        .strict_cast(polars::prelude::DataType::Datetime(
+                            polars::prelude::TimeUnit::Nanoseconds,
+                            None,
+                        ))
+                        .into()
+                }),
+            Value::Duration { val, .. } => Ok(val
+                .to_owned()
+                .lit()
+                .strict_cast(polars::prelude::DataType::Duration(
+                    polars::prelude::TimeUnit::Nanoseconds,
+                ))
+                .into()),
             x => Err(ShellError::CantConvert {
                 to_type: "lazy expression".into(),
                 from_type: x.get_type().to_string(),