Using try_from_value for NuSchema

crates/nu_plugin_polars/src/dataframe/command/core/open.rs

@@ -163,7 +163,7 @@ fn command(
         });
     }
 
-    let hive_options = build_hive_options(call)?;
+    let hive_options = build_hive_options(plugin, call)?;
 
     match type_option {
         Some((ext, blamed)) => match PolarsFileType::from(ext.as_str()) {
@@ -388,7 +388,7 @@ fn from_json(
     })?;
     let maybe_schema = call
         .get_flag("schema")?
-        .map(|schema| NuSchema::try_from(&schema))
+        .map(|schema| NuSchema::try_from_value(plugin, &schema))
         .transpose()?;
 
     let buf_reader = BufReader::new(file);
@@ -429,11 +429,7 @@ fn from_ndjson(
             NonZeroUsize::new(DEFAULT_INFER_SCHEMA)
                 .expect("The default infer-schema should be non zero"),
         );
-    let maybe_schema = call
+    let maybe_schema = get_schema(plugin, call)?;
-        .get_flag("schema")?
-        .map(|schema| NuSchema::try_from(&schema))
-        .transpose()?;
-
     if !is_eager {
         let start_time = std::time::Instant::now();
 
@@ -511,10 +507,7 @@ fn from_csv(
         .unwrap_or(DEFAULT_INFER_SCHEMA);
     let skip_rows: Option<usize> = call.get_flag("skip-rows")?;
     let columns: Option<Vec<String>> = call.get_flag("columns")?;
-    let maybe_schema = call
+    let maybe_schema = get_schema(plugin, call)?;
-        .get_flag("schema")?
-        .map(|schema| NuSchema::try_from(&schema))
-        .transpose()?;
     let truncate_ragged_lines: bool = call.has_flag("truncate-ragged-lines")?;
 
     if !is_eager {
@@ -627,12 +620,15 @@ fn cloud_not_supported(file_type: PolarsFileType, span: Span) -> ShellError {
     }
 }
 
-fn build_hive_options(call: &EvaluatedCall) -> Result<HiveOptions, ShellError> {
+fn build_hive_options(
+    plugin: &PolarsPlugin,
+    call: &EvaluatedCall,
+) -> Result<HiveOptions, ShellError> {
     let enabled: Option<bool> = call.get_flag("hive-enabled")?;
     let hive_start_idx: Option<usize> = call.get_flag("hive-start-idx")?;
     let schema: Option<NuSchema> = call
         .get_flag::<Value>("hive-schema")?
-        .map(|schema| NuSchema::try_from(&schema))
+        .map(|schema| NuSchema::try_from_value(plugin, &schema))
         .transpose()?;
     let try_parse_dates: bool = call.has_flag("hive-try-parse-dates")?;
 
@@ -643,3 +639,11 @@ fn build_hive_options(call: &EvaluatedCall) -> Result<HiveOptions, ShellError> {
         try_parse_dates,
     })
 }
+
+fn get_schema(plugin: &PolarsPlugin, call: &EvaluatedCall) -> Result<Option<NuSchema>, ShellError> {
+    let schema: Option<NuSchema> = call
+        .get_flag("schema")?
+        .map(|schema| NuSchema::try_from_value(plugin, &schema))
+        .transpose()?;
+    Ok(schema)
+}

crates/nu_plugin_polars/src/dataframe/command/core/to_df.rs

@@ -206,7 +206,7 @@ impl PluginCommand for ToDataFrame {
     ) -> Result<PipelineData, LabeledError> {
         let maybe_schema = call
             .get_flag("schema")?
-            .map(|schema| NuSchema::try_from(&schema))
+            .map(|schema| NuSchema::try_from_value(plugin, &schema))
             .transpose()?;
 
         debug!("schema: {:?}", maybe_schema);

crates/nu_plugin_polars/src/dataframe/command/core/to_lazy.rs

@@ -54,7 +54,7 @@ impl PluginCommand for ToLazyFrame {
     ) -> Result<PipelineData, LabeledError> {
         let maybe_schema = call
             .get_flag("schema")?
-            .map(|schema| NuSchema::try_from(&schema))
+            .map(|schema| NuSchema::try_from_value(plugin, &schema))
             .transpose()?;
 
         let df = NuDataFrame::try_from_iter(plugin, input.into_iter(), maybe_schema)?;

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

@@ -7,7 +7,7 @@ use nu_protocol::{ShellError, Span, Value};
 use polars::prelude::{DataType, Field, Schema, SchemaExt, SchemaRef};
 use uuid::Uuid;
 
-use crate::Cacheable;
+use crate::{Cacheable, PolarsPlugin};
 
 use super::{str_to_dtype, CustomValueSupport, PolarsPluginObject, PolarsPluginType};
 
@@ -26,14 +26,6 @@ impl NuSchema {
     }
 }
 
-impl TryFrom<&Value> for NuSchema {
-    type Error = ShellError;
-    fn try_from(value: &Value) -> Result<Self, Self::Error> {
-        let schema = value_to_schema(value, Span::unknown())?;
-        Ok(Self::new(Arc::new(schema)))
-    }
-}
-
 impl From<NuSchema> for SchemaRef {
     fn from(val: NuSchema) -> Self {
         Arc::clone(&val.schema)
@@ -86,6 +78,24 @@ impl CustomValueSupport for NuSchema {
     fn base_value(self, span: Span) -> Result<Value, ShellError> {
         Ok(fields_to_value(self.schema.iter_fields(), span))
     }
+
+    fn try_from_value(plugin: &PolarsPlugin, value: &Value) -> Result<Self, ShellError> {
+        if let Value::Custom { val, .. } = value {
+            if let Some(cv) = val.as_any().downcast_ref::<Self::CV>() {
+                Self::try_from_custom_value(plugin, cv)
+            } else {
+                Err(ShellError::CantConvert {
+                    to_type: Self::get_type_static().to_string(),
+                    from_type: value.get_type().to_string(),
+                    span: value.span(),
+                    help: None,
+                })
+            }
+        } else {
+            let schema = value_to_schema(value, Span::unknown())?;
+            Ok(Self::new(Arc::new(schema)))
+        }
+    }
 }
 
 fn fields_to_value(fields: impl Iterator<Item = Field>, span: Span) -> Value {