Add setters to some provenance fields

Most of the fields of the e3.slsa.provenance classes are read-only.
Some of those may be set at provenance creation time, but (for
instance) the RunDetails started_on and finished_on should be writable.

Here is the list of fields which should be writable
- `Builder.id` if the provenance is created before the build ID is
   actually created
- `BuildMetadata.finished_on`, or the builds needs to be finished when
  the provenance is created
- BuildMetadata.started_on, to allow setting it at real build start
  time.

Closes #43+

Author: grouigrokon

src/e3/slsa/provenance.py

@@ -149,6 +149,10 @@ def id(self) -> TypeURI:
         """  # noqa RST304
         return self.__id
 
+    @id.setter
+    def id(self, value: str | TypeURI) -> None:
+        self.__id = value if isinstance(value, TypeURI) else TypeURI(value)
+
     @property
     def version(self) -> dict[str, str]:
         """Builder version mapping.
@@ -279,6 +283,10 @@ def finished_on(self) -> datetime:
         """The timestamp of when the build completed."""
         return self.__finished_on
 
+    @finished_on.setter
+    def finished_on(self, value: datetime | str) -> None:
+        self.__finished_on = self.__validate_timestamp(value)
+
     @property
     def invocation_id(self) -> str:
         """Build invocation identifier.
@@ -299,6 +307,10 @@ def started_on(self) -> datetime:
         """The timestamp of when the build started."""
         return self.__started_on
 
+    @started_on.setter
+    def started_on(self, value: datetime | str) -> None:
+        self.__started_on = self.__validate_timestamp(value)
+
     # --------------------------- Public methods ---------------------------- #
 
     def as_dict(self) -> dict:
@@ -380,13 +392,20 @@ def load_json(cls, initializer: str) -> BuildMetadata:
     # --------------------------- Private methods --------------------------- #
 
     @staticmethod
-    def __validate_timestamp(timestamp: datetime) -> datetime:
+    def __validate_timestamp(timestamp: datetime | str) -> datetime:
         """Validate a timestamp."""
-        valid_timestamp: datetime
-        if isinstance(timestamp, datetime):
+        valid_timestamp: datetime | None = None
+        if isinstance(timestamp, str):
+            valid_timestamp = date_parser.parse(timestamp)
+        elif isinstance(timestamp, datetime):
+            valid_timestamp = timestamp
+
+        if isinstance(valid_timestamp, datetime):
             # When converting to JSON representation, the microseconds
             # are lost. Just remove them.
-            valid_timestamp = timestamp.astimezone(timezone.utc).replace(microsecond=0)
+            valid_timestamp = valid_timestamp.astimezone(timezone.utc).replace(
+                microsecond=0
+            )
         else:
             raise TypeError(f"Invalid timestamp type {type(timestamp)}")
 

tests/tests_e3/slsa/provenance_test.py

@@ -237,7 +237,7 @@ def test_builder_as_dict() -> None:
     dict_dep: dict = desc.as_dict()
     assert json.dumps(dict_repr, indent="  ") != ""
     assert dict_repr.get(Builder.ATTR_BUILD_ID) == build_id
-    assert dict_repr.get(Builder.ATTR_BUILDER_DEPENDENCIES)[0] == dict_dep
+    assert dict_repr.get(Builder.ATTR_BUILDER_DEPENDENCIES, [])[0] == dict_dep
     assert dict_repr.get(Builder.ATTR_VERSION) == version
 
 
@@ -264,6 +264,13 @@ def test_builder_init() -> None:
     assert builder.version == version
     # Test the __eq__ method with a wrong type.
     assert builder != {}
+    # Test setting the builder ID
+    builder_id: str = "protocol://path/file"
+    builder.id = builder_id
+    builder.id = TypeURI(builder_id)
+    with pytest.raises(ValueError) as invalid_builder_id:
+        builder.id = None
+    assert "Invalid URI None" in invalid_builder_id.value.args[0]
 
 
 def test_builder_load_dict() -> None:
@@ -333,6 +340,20 @@ def test_buildmetadata_init() -> None:
             invocation_id=invocation_id, started_on=None, finished_on=finish_time
         )
     assert "Invalid timestamp type" in invalid_timestamp_type.value.args[0]
+    # Set start and finish times with datetime, string or invalid values.
+    test_time: str = "2025-04-16T07:32:19Z"
+    bm.started_on = test_time
+    bm.started_on = date_parser.parse(test_time)
+    with pytest.raises(TypeError) as invalid_timestamp_type:
+        # noinspection PyTypeChecker
+        bm.started_on = None
+    assert "Invalid timestamp type" in invalid_timestamp_type.value.args[0]
+    bm.finished_on = test_time
+    bm.finished_on = date_parser.parse(test_time)
+    with pytest.raises(TypeError) as invalid_timestamp_type:
+        # noinspection PyTypeChecker
+        bm.finished_on = None
+    assert "Invalid timestamp type" in invalid_timestamp_type.value.args[0]
 
 
 def test_buildmetadata_load_dict() -> None: