fix: Projection pushdown was ignored by include_file_paths (#19341)

crates/polars-plan/src/plans/optimizer/projection_pushdown/mod.rs

@@ -511,6 +511,21 @@ impl ProjectionPushDown {
                         file_options.row_index = None;
                     }
                 };
+
+                if let Some(col_name) = &file_options.include_file_paths {
+                    if output_schema
+                        .as_ref()
+                        .map_or(false, |schema| !schema.contains(col_name))
+                    {
+                        // Need to remove it from the input schema so
+                        // that projection indices are correct.
+                        let mut file_schema = Arc::unwrap_or_clone(file_info.schema);
+                        file_schema.shift_remove(col_name);
+                        file_info.schema = Arc::new(file_schema);
+                        file_options.include_file_paths = None;
+                    }
+                };
+
                 let lp = Scan {
                     sources,
                     file_info,

py-polars/tests/unit/io/test_scan.py

@@ -801,3 +801,11 @@ def test_scan_double_collect_row_index_invalidates_cached_ir_18892() -> None:
             schema={"index": pl.UInt32, "a": pl.Int64},
         ),
     )
+
+
+def test_scan_include_file_paths_respects_projection_pushdown() -> None:
+    q = pl.scan_csv(b"a,b,c\na1,b1,c1", include_file_paths="path_name").select(
+        ["a", "b"]
+    )
+
+    assert_frame_equal(q.collect(), pl.DataFrame({"a": "a1", "b": "b1"}))