feat(core): drop default value for write disposition (#1057)

* feat(core): drop default value for write disposition

* don't use default value in apply_hints

* applies default write disposition in empty apply hints

---------

Co-authored-by: Marcin Rudolf <[email protected]>

dlt/common/schema/schema.py

@@ -82,7 +82,9 @@ class Schema:
     _imported_version_hash: str  # version hash of recently imported schema
     _schema_description: str  # optional schema description
     _schema_tables: TSchemaTables
-    _settings: TSchemaSettings  # schema settings to hold default hints, preferred types and other settings
+    _settings: (
+        TSchemaSettings  # schema settings to hold default hints, preferred types and other settings
+    )
 
     # list of preferred types: map regex on columns into types
     _compiled_preferred_types: List[Tuple[REPattern, TDataType]]

dlt/extract/hints.py

@@ -82,6 +82,8 @@ def make_hints(
     )
     if not table_name:
         new_template.pop("name")
+    if not write_disposition and "write_disposition" in new_template:
+        new_template.pop("write_disposition")
     # remember original columns
     if columns is not None:
         new_template["original_columns"] = columns
@@ -197,10 +199,11 @@ def apply_hints(
         """
         if not self._hints:
             # if there is no template yet, create and set a new one.
+            default_wd = None if parent_table_name else DEFAULT_WRITE_DISPOSITION
             t = make_hints(
                 table_name,
                 parent_table_name,
-                write_disposition,
+                write_disposition or default_wd,
                 columns,
                 primary_key,
                 merge_key,

tests/extract/test_extract.py

@@ -89,6 +89,14 @@ def table_name_with_lambda(_range):
     assert "table_name_with_lambda" not in schema.tables
 
 
+def test_make_hints_default() -> None:
+    hints = make_hints()
+    assert hints == {"columns": {}}
+
+    hints = make_hints(write_disposition=None)
+    assert hints == {"columns": {}}
+
+
 def test_extract_hints_mark(extract_step: Extract) -> None:
     @dlt.resource
     def with_table_hints():

tests/extract/test_sources.py

@@ -1326,9 +1326,11 @@ def empty_gen():
 
     empty_r = empty()
     with pytest.raises(InconsistentTableTemplate):
-        empty_r.apply_hints(parent_table_name=lambda ev: ev["p"])
+        empty_r.apply_hints(parent_table_name=lambda ev: ev["p"], write_disposition=None)
 
-    empty_r.apply_hints(table_name=lambda ev: ev["t"], parent_table_name=lambda ev: ev["p"])
+    empty_r.apply_hints(
+        table_name=lambda ev: ev["t"], parent_table_name=lambda ev: ev["p"], write_disposition=None
+    )
     assert empty_r._table_name_hint_fun is not None
     assert empty_r._table_has_other_dynamic_hints is True
 
@@ -1360,6 +1362,15 @@ def empty_gen():
     assert table["columns"]["tags"] == {"name": "tags"}
 
 
+def test_resource_no_template() -> None:
+    empty = DltResource.from_data([1, 2, 3], name="table")
+    assert empty.write_disposition == "append"
+    assert empty.compute_table_schema()["write_disposition"] == "append"
+    empty.apply_hints()
+    assert empty.write_disposition == "append"
+    assert empty.compute_table_schema()["write_disposition"] == "append"
+
+
 def test_selected_pipes_with_duplicates():
     def input_gen():
         yield from [1, 2, 3]