Implement "replace" transformation in Field operation module

python/mlcroissant/mlcroissant/_src/operation_graph/operations/field.py

@@ -63,6 +63,20 @@ def _apply_transform_fn(value: Any, transform: Transform, field: Field) -> Any:
             raise ValueError(f"`format` only applies to dates. Got {field.data_type}")
     elif transform.separator is not None:
         return value.split(transform.separator)
+    elif transform.replace is not None:
+        if isinstance(value, pathlib.PurePath):
+            value = os.fspath(value)
+        # split on unescaped slash
+        parts = re.split(r"(?<!\\)/", transform.replace)
+        if len(parts) != 2:
+            raise ValueError(
+                "`replace` must have exactly one unescaped slash. "
+                f"Got {transform.replace} which has "
+                f"{len(parts) - 1} unescaped slashes."
+            )
+        parts = [part.replace("\\/", "/") for part in parts]
+        pattern, replacement = parts
+        return re.sub(pattern, replacement, value)
     return value
 
 

python/mlcroissant/mlcroissant/_src/operation_graph/operations/field_test.py

@@ -372,6 +372,27 @@ def test_extract_lines(separator):
             "2024-12-10",
             False,
         ],
+        [
+            "foo",
+            Source(transforms=[Transform(replace="foo/bar")]),
+            DataType.TEXT,
+            "bar",
+            False,
+        ],
+        [
+            "path/to/a/file",
+            Source(transforms=[Transform(replace=r"path\/to\/a/some\/new\/path")]),
+            DataType.TEXT,
+            "some/new/path/file",
+            False,
+        ],
+        [
+            "123",
+            Source(transforms=[Transform(replace=r"[0-9]+([0-9])/abc\1")]),
+            DataType.TEXT,
+            "abc3",
+            False,
+        ],
     ],
 )
 def test_apply_transforms_fn(value, source, data_type, expected_value, repeated):