refactor(rust): Move expression expansion to conversion module

crates/polars-plan/src/dsl/meta.rs

@@ -3,7 +3,7 @@ use std::ops::BitAnd;
 
 use super::*;
 use crate::logical_plan::alp::tree_format::TreeFmtVisitor;
-use crate::logical_plan::expr_expansion::is_regex_projection;
+use crate::logical_plan::conversion::is_regex_projection;
 use crate::logical_plan::visitor::{AexprNode, TreeWalker};
 
 /// Specialized expressions for Categorical dtypes.

crates/polars-plan/src/dsl/struct_.rs

@@ -1,5 +1,5 @@
 use super::*;
-use crate::logical_plan::expr_expansion::is_regex_projection;
+use crate::logical_plan::conversion::is_regex_projection;
 
 /// Specialized expressions for Struct dtypes.
 pub struct StructNameSpace(pub(crate) Expr);

crates/polars-plan/src/logical_plan/builder_dsl.rs

@@ -12,20 +12,10 @@ use polars_io::HiveOptions;
 use polars_io::RowIndex;
 
 use crate::constants::UNLIMITED_CACHE;
-use crate::logical_plan::expr_expansion::rewrite_projections;
 #[cfg(feature = "python")]
 use crate::prelude::python_udf::PythonFunction;
 use crate::prelude::*;
 
-pub(crate) fn prepare_projection(
-    exprs: Vec<Expr>,
-    schema: &Schema,
-) -> PolarsResult<(Vec<Expr>, Schema)> {
-    let exprs = rewrite_projections(exprs, schema, &[])?;
-    let schema = expressions_to_schema(&exprs, schema, Context::Default)?;
-    Ok((exprs, schema))
-}
-
 pub struct DslBuilder(pub DslPlan);
 
 impl From<DslPlan> for DslBuilder {

crates/polars-plan/src/logical_plan/conversion/dsl_to_ir.rs

@@ -1,6 +1,7 @@
+use expr_expansion::{is_regex_projection, rewrite_projections};
+
 use super::stack_opt::ConversionOpt;
 use super::*;
-use crate::logical_plan::expr_expansion::{is_regex_projection, rewrite_projections};
 use crate::logical_plan::projection_expr::ProjectionExprs;
 
 fn expand_expressions(

crates/polars-plan/src/logical_plan/expr_expansion.rs → crates/polars-plan/src/logical_plan/conversion/expr_expansion.rs

@@ -1,6 +1,15 @@
 //! this contains code used for rewriting projections, expanding wildcards, regex selection etc.
 use super::*;
 
+pub(crate) fn prepare_projection(
+    exprs: Vec<Expr>,
+    schema: &Schema,
+) -> PolarsResult<(Vec<Expr>, Schema)> {
+    let exprs = rewrite_projections(exprs, schema, &[])?;
+    let schema = expressions_to_schema(&exprs, schema, Context::Default)?;
+    Ok((exprs, schema))
+}
+
 /// This replaces the wildcard Expr with a Column Expr. It also removes the Exclude Expr from the
 /// expression chain.
 pub(super) fn replace_wildcard_with_column(expr: Expr, column_name: Arc<str>) -> Expr {

crates/polars-plan/src/logical_plan/conversion/mod.rs

@@ -1,5 +1,6 @@
 mod convert_utils;
 mod dsl_to_ir;
+mod expr_expansion;
 mod expr_to_ir;
 mod ir_to_dsl;
 #[cfg(any(feature = "ipc", feature = "parquet", feature = "csv"))]
@@ -16,6 +17,8 @@ use polars_utils::vec::ConvertVec;
 use recursive::recursive;
 pub(crate) mod type_coercion;
 
+pub(crate) use expr_expansion::{is_regex_projection, prepare_projection, rewrite_projections};
+
 use crate::constants::get_len_name;
 use crate::prelude::*;
 

crates/polars-plan/src/logical_plan/functions/dsl.rs

@@ -1,5 +1,5 @@
 use super::*;
-use crate::logical_plan::expr_expansion::rewrite_projections;
+use crate::logical_plan::conversion::rewrite_projections;
 
 // Except for Opaque functions, this only has the DSL name of the function.
 #[derive(Clone)]

crates/polars-plan/src/logical_plan/mod.rs

@@ -6,9 +6,7 @@ use std::sync::Arc;
 use polars_core::prelude::*;
 use recursive::recursive;
 
-use crate::logical_plan::DslPlan::DataFrameScan;
 use crate::prelude::*;
-use crate::utils::{expr_to_leaf_column_names, get_single_leaf};
 
 pub(crate) mod aexpr;
 pub(crate) mod alp;
@@ -20,7 +18,6 @@ mod builder_ir;
 pub(crate) mod conversion;
 #[cfg(feature = "debugging")]
 pub(crate) mod debug;
-pub(crate) mod expr_expansion;
 pub mod expr_ir;
 mod file_scan;
 mod format;
@@ -206,7 +203,7 @@ impl Default for DslPlan {
     fn default() -> Self {
         let df = DataFrame::new::<Series>(vec![]).unwrap();
         let schema = df.schema();
-        DataFrameScan {
+        DslPlan::DataFrameScan {
             df: Arc::new(df),
             schema: Arc::new(schema),
             output_schema: None,