chore: fix clippy issue that occur with only defaults (#1802)

# Description
Executing `cargo clippy --tests` in `crates/deltalake-core` resulted in
some failures in test_utils due to a dependency on features that only
exist when datafusion is enabled.

Clippy now works with default features and with datafusion enabled.

Co-authored-by: Will Jones <willjones127@gmail.com>

crates/deltalake-core/src/operations/delete.rs

@@ -315,9 +315,9 @@ mod tests {
     use crate::operations::DeltaOps;
     use crate::protocol::*;
     use crate::writer::test_utils::datafusion::get_data;
+    use crate::writer::test_utils::datafusion::write_batch;
     use crate::writer::test_utils::{
         get_arrow_schema, get_delta_schema, get_record_batch, setup_table_with_configuration,
-        write_batch,
     };
     use crate::DeltaConfigKey;
     use crate::DeltaTable;

crates/deltalake-core/src/operations/update.rs

@@ -461,9 +461,9 @@ impl std::future::IntoFuture for UpdateBuilder {
 mod tests {
     use crate::operations::DeltaOps;
     use crate::writer::test_utils::datafusion::get_data;
+    use crate::writer::test_utils::datafusion::write_batch;
     use crate::writer::test_utils::{
         get_arrow_schema, get_delta_schema, get_record_batch, setup_table_with_configuration,
-        write_batch,
     };
     use crate::DeltaConfigKey;
     use crate::DeltaTable;

crates/deltalake-core/src/operations/write.rs

@@ -565,9 +565,10 @@ mod tests {
     use crate::operations::{collect_sendable_stream, DeltaOps};
     use crate::protocol::SaveMode;
     use crate::writer::test_utils::datafusion::get_data;
+    use crate::writer::test_utils::datafusion::write_batch;
     use crate::writer::test_utils::{
         get_delta_schema, get_delta_schema_with_nested_struct, get_record_batch,
-        get_record_batch_with_nested_struct, setup_table_with_configuration, write_batch,
+        get_record_batch_with_nested_struct, setup_table_with_configuration,
     };
     use crate::DeltaConfigKey;
     use arrow::datatypes::Field;

crates/deltalake-core/src/writer/test_utils.rs

@@ -10,7 +10,6 @@ use arrow_schema::{DataType, Field, Schema as ArrowSchema};
 use crate::operations::{create::CreateBuilder, DeltaOps};
 use crate::schema::{Schema, SchemaTypeStruct};
 use crate::table::DeltaTableMetaData;
-use crate::writer::SaveMode;
 use crate::{DeltaConfigKey, DeltaTable, DeltaTableBuilder, SchemaDataType, SchemaField};
 
 pub type TestResult = Result<(), Box<dyn std::error::Error + 'static>>;
@@ -49,14 +48,6 @@ pub fn get_record_batch(part: Option<String>, with_null: bool) -> RecordBatch {
     }
 }
 
-pub async fn write_batch(table: DeltaTable, batch: RecordBatch) -> DeltaTable {
-    DeltaOps(table)
-        .write(vec![batch.clone()])
-        .with_save_mode(SaveMode::Append)
-        .await
-        .expect("Failed to append")
-}
-
 pub fn get_arrow_schema(part: &Option<String>) -> Arc<ArrowSchema> {
     match part {
         Some(key) if key.contains("/id=") => Arc::new(ArrowSchema::new(vec![Field::new(
@@ -331,6 +322,8 @@ pub async fn create_initialized_table(partition_cols: &[String]) -> DeltaTable {
 
 #[cfg(feature = "datafusion")]
 pub mod datafusion {
+    use crate::operations::DeltaOps;
+    use crate::writer::SaveMode;
     use crate::DeltaTable;
     use arrow_array::RecordBatch;
     use datafusion::prelude::SessionContext;
@@ -347,4 +340,12 @@ pub mod datafusion {
             .await
             .unwrap()
     }
+
+    pub async fn write_batch(table: DeltaTable, batch: RecordBatch) -> DeltaTable {
+        DeltaOps(table)
+            .write(vec![batch.clone()])
+            .with_save_mode(SaveMode::Append)
+            .await
+            .expect("Failed to append")
+    }
 }