Make metadata lazy for table row classes

docs/conf.py

@@ -307,6 +307,7 @@ def handle_item(fieldarg, content):
     ("c:type", "uint32_t"),
     ("c:type", "bool"),
     ("py:class", "tskit.metadata.AbstractMetadataCodec"),
+    ("py:class", "tskit.trees.Site"),
     # TODO these have been triaged here to make the docs compile, but we should
     # sort them out properly. https://github.com/tskit-dev/tskit/issues/336
     ("py:class", "array_like"),

python/CHANGELOG.rst

@@ -4,11 +4,20 @@
 
 **Breaking changes**
 
+- `Mutation.position` and `Mutation.index` which were deprecated in 0.2.2 (Sep '19) have
+  been removed.
+
 **Features**
 
 - SVG visualization of a single tree allows all mutations on an edge to be plotted
   via the ``all_edge_mutations`` param (:user:`hyanwong`,:issue:`1253`, :pr:`1258`).
 
+- Entity classes such as `Mutation`, `Node` are now python dataclasses
+  (:user:`benjeffery`, :pr:`1261`).
+
+- Metadata decoding for table row access is now lazy (:user:`benjeffery`, :pr:`1261`).
+
+
 **Fixes**
 
 --------------------

python/tests/__init__.py

@@ -234,13 +234,13 @@ def __init__(self, tree_sequence, breakpoints=None):
         def make_mutation(id_):
             site, node, derived_state, parent, metadata, time = ll_ts.get_mutation(id_)
             return tskit.Mutation(
-                id_=id_,
+                id=id_,
                 site=site,
                 node=node,
                 time=time,
                 derived_state=derived_state,
                 parent=parent,
-                encoded_metadata=metadata,
+                metadata=metadata,
                 metadata_decoder=tskit.metadata.parse_metadata_schema(
                     ll_ts.get_table_metadata_schemas().mutation
                 ).decode_row,
@@ -250,11 +250,11 @@ def make_mutation(id_):
             pos, ancestral_state, ll_mutations, id_, metadata = ll_ts.get_site(j)
             self._sites.append(
                 tskit.Site(
-                    id_=id_,
+                    id=id_,
                     position=pos,
                     ancestral_state=ancestral_state,
                     mutations=[make_mutation(ll_mut) for ll_mut in ll_mutations],
-                    encoded_metadata=metadata,
+                    metadata=metadata,
                     metadata_decoder=tskit.metadata.parse_metadata_schema(
                         ll_ts.get_table_metadata_schemas().site
                     ).decode_row,

python/tests/test_highlevel.py

@@ -1241,17 +1241,7 @@ def verify_mutations(self, ts):
         assert ts.num_mutations == len(other_mutations)
         assert ts.num_mutations == len(mutations)
         for mut, other_mut in zip(mutations, other_mutations):
-            # We cannot compare these directly as the mutations obtained
-            # from the mutations iterator will have extra deprecated
-            # attributes.
-            assert mut.id == other_mut.id
-            assert mut.site == other_mut.site
-            assert mut.parent == other_mut.parent
-            assert mut.node == other_mut.node
-            assert mut.metadata == other_mut.metadata
-            # Check the deprecated attrs.
-            assert mut.position == ts.site(mut.site).position
-            assert mut.index == mut.site
+            assert mut == other_mut
 
     def test_sites_mutations(self):
         # Check that the mutations iterator returns the correct values.
@@ -2103,17 +2093,7 @@ def verify_mutations(self, tree):
         assert tree.num_mutations == len(other_mutations)
         assert tree.num_mutations == len(mutations)
         for mut, other_mut in zip(mutations, other_mutations):
-            # We cannot compare these directly as the mutations obtained
-            # from the mutations iterator will have extra deprecated
-            # attributes.
-            assert mut.id == other_mut.id
-            assert mut.site == other_mut.site
-            assert mut.parent == other_mut.parent
-            assert mut.node == other_mut.node
-            assert mut.metadata == other_mut.metadata
-            # Check the deprecated attrs.
-            assert mut.position == tree.tree_sequence.site(mut.site).position
-            assert mut.index == mut.site
+            assert mut == other_mut
 
     def test_simple_mutations(self):
         tree = self.get_tree()
@@ -2991,17 +2971,18 @@ def test_metadata(self):
         (inst,) = self.get_instances(1)
         (inst2,) = self.get_instances(1)
         assert inst == inst2
-        inst._metadata_decoder = lambda m: "different decoder"
+        inst.metadata
         assert inst == inst2
-        inst._encoded_metadata = b"different"
-        assert not (inst == inst2)
+        inst._metadata = "different"
+        assert inst != inst2
 
     def test_decoder_run_once(self):
         # For a given instance, the decoded metadata should be cached, with the decoder
         # called once
         (inst,) = self.get_instances(1)
         times_run = 0
 
+        # Hack in a tracing decoder
         def decoder(m):
             nonlocal times_run
             times_run += 1
@@ -3019,12 +3000,12 @@ class TestIndividualContainer(SimpleContainersMixin, SimpleContainersWithMetadat
     def get_instances(self, n):
         return [
             tskit.Individual(
-                id_=j,
+                id=j,
                 flags=j,
                 location=[j],
                 parents=[j],
                 nodes=[j],
-                encoded_metadata=b"x" * j,
+                metadata=b"x" * j,
                 metadata_decoder=lambda m: m.decode() + "decoded",
             )
             for j in range(n)
@@ -3035,12 +3016,12 @@ class TestNodeContainer(SimpleContainersMixin, SimpleContainersWithMetadataMixin
     def get_instances(self, n):
         return [
             tskit.Node(
-                id_=j,
+                id=j,
                 flags=j,
                 time=j,
                 population=j,
                 individual=j,
-                encoded_metadata=b"x" * j,
+                metadata=b"x" * j,
                 metadata_decoder=lambda m: m.decode() + "decoded",
             )
             for j in range(n)
@@ -3055,9 +3036,9 @@ def get_instances(self, n):
                 right=j,
                 parent=j,
                 child=j,
-                encoded_metadata=b"x" * j,
+                metadata=b"x" * j,
                 metadata_decoder=lambda m: m.decode() + "decoded",
-                id_=j,
+                id=j,
             )
             for j in range(n)
         ]
@@ -3067,11 +3048,11 @@ class TestSiteContainer(SimpleContainersMixin, SimpleContainersWithMetadataMixin
     def get_instances(self, n):
         return [
             tskit.Site(
-                id_=j,
+                id=j,
                 position=j,
                 ancestral_state="A" * j,
                 mutations=TestMutationContainer().get_instances(j),
-                encoded_metadata=b"x" * j,
+                metadata=b"x" * j,
                 metadata_decoder=lambda m: m.decode() + "decoded",
             )
             for j in range(n)
@@ -3082,46 +3063,46 @@ class TestMutationContainer(SimpleContainersMixin, SimpleContainersWithMetadataM
     def get_instances(self, n):
         return [
             tskit.Mutation(
-                id_=j,
+                id=j,
                 site=j,
                 node=j,
                 time=j,
                 derived_state="A" * j,
                 parent=j,
-                encoded_metadata=b"x" * j,
+                metadata=b"x" * j,
                 metadata_decoder=lambda m: m.decode() + "decoded",
             )
             for j in range(n)
         ]
 
     def test_nan_equality(self):
         a = tskit.Mutation(
-            id_=42,
+            id=42,
             site=42,
             node=42,
             time=UNKNOWN_TIME,
             derived_state="A" * 42,
             parent=42,
-            encoded_metadata=b"x" * 42,
+            metadata=b"x" * 42,
             metadata_decoder=lambda m: m.decode() + "decoded",
         )
         b = tskit.Mutation(
-            id_=42,
+            id=42,
             site=42,
             node=42,
             derived_state="A" * 42,
             parent=42,
-            encoded_metadata=b"x" * 42,
+            metadata=b"x" * 42,
             metadata_decoder=lambda m: m.decode() + "decoded",
         )
         c = tskit.Mutation(
-            id_=42,
+            id=42,
             site=42,
             node=42,
             time=math.nan,
             derived_state="A" * 42,
             parent=42,
-            encoded_metadata=b"x" * 42,
+            metadata=b"x" * 42,
             metadata_decoder=lambda m: m.decode() + "decoded",
         )
         assert a == a
@@ -3139,13 +3120,14 @@ class TestMigrationContainer(SimpleContainersMixin, SimpleContainersWithMetadata
     def get_instances(self, n):
         return [
             tskit.Migration(
+                id=j,
                 left=j,
                 right=j,
                 node=j,
                 source=j,
                 dest=j,
                 time=j,
-                encoded_metadata=b"x" * j,
+                metadata=b"x" * j,
                 metadata_decoder=lambda m: m.decode() + "decoded",
             )
             for j in range(n)
@@ -3156,8 +3138,8 @@ class TestPopulationContainer(SimpleContainersMixin, SimpleContainersWithMetadat
     def get_instances(self, n):
         return [
             tskit.Population(
-                id_=j,
-                encoded_metadata=b"x" * j,
+                id=j,
+                metadata=b"x" * j,
                 metadata_decoder=lambda m: m.decode() + "decoded",
             )
             for j in range(n)
@@ -3167,7 +3149,7 @@ def get_instances(self, n):
 class TestProvenanceContainer(SimpleContainersMixin):
     def get_instances(self, n):
         return [
-            tskit.Provenance(id_=j, timestamp="x" * j, record="y" * j) for j in range(n)
+            tskit.Provenance(id=j, timestamp="x" * j, record="y" * j) for j in range(n)
         ]
 
 

python/tests/test_stats.py

@@ -108,11 +108,17 @@ def verify_max_distance(self, ts):
         A = ldc.get_r2_matrix()
         j = len(mutations) // 2
         for k in range(j):
-            x = mutations[j + k].position - mutations[j].position
+            x = (
+                ts.site(mutations[j + k].site).position
+                - ts.site(mutations[j].site).position
+            )
             a = ldc.get_r2_array(j, max_distance=x)
             assert a.shape[0] == k
             assert np.allclose(A[j, j + 1 : j + 1 + k], a)
-            x = mutations[j].position - mutations[j - k].position
+            x = (
+                ts.site(mutations[j].site).position
+                - ts.site(mutations[j - k].site).position
+            )
             a = ldc.get_r2_array(j, max_distance=x, direction=tskit.REVERSE)
             assert a.shape[0] == k
             assert np.allclose(A[j, j - k : j], a[::-1])

python/tskit/metadata.py

@@ -23,11 +23,13 @@
 Classes for metadata decoding, encoding and validation
 """
 import abc
+import builtins
 import collections
 import copy
 import json
 import pprint
 import struct
+import types
 from itertools import islice
 from typing import Any
 from typing import Mapping
@@ -39,6 +41,8 @@
 import tskit
 import tskit.exceptions as exceptions
 
+__builtins__object__setattr__ = builtins.object.__setattr__
+
 
 def replace_root_refs(obj):
     if type(obj) == list:
@@ -656,3 +660,56 @@ def parse_metadata_schema(encoded_schema: str) -> MetadataSchema:
         except json.decoder.JSONDecodeError:
             raise ValueError(f"Metadata schema is not JSON, found {encoded_schema}")
         return MetadataSchema(decoded)
+
+
+class _CachedMetadata:
+    """
+    Descriptor for lazy decoding of metadata on attribute access.
+    """
+
+    def __get__(self, row, owner):
+        if row._metadata_decoder is not None:
+            # Some classes that use this are frozen so we need to directly setattr.
+            __builtins__object__setattr__(
+                row, "_metadata", row._metadata_decoder(row._metadata)
+            )
+            # Decoder being None indicates that metadata is decoded
+            __builtins__object__setattr__(row, "_metadata_decoder", None)
+        return row._metadata
+
+    def __set__(self, row, value):
+        __builtins__object__setattr__(row, "_metadata", value)
+
+
+def lazy_decode(cls):
+    """
+    Modifies a dataclass such that it lazily decodes metadata, if it is encoded.
+    If the metadata passed to the constructor is encoded a `metadata_decoder` parameter
+    must be also be passed.
+    """
+    wrapped_init = cls.__init__
+
+    # Intercept the init to record the decoder
+    def new_init(self, *args, metadata_decoder=None, **kwargs):
+        __builtins__object__setattr__(self, "_metadata_decoder", metadata_decoder)
+        wrapped_init(self, *args, **kwargs)
+
+    cls.__init__ = new_init
+
+    # Add a descriptor to the class to decode and cache metadata
+    cls.metadata = _CachedMetadata()
+
+    # Add slots needed to the class
+    slots = cls.__slots__
+    slots.extend(["_metadata", "_metadata_decoder"])
+    dict_ = dict()
+    sloted_members = dict()
+    for k, v in cls.__dict__.items():
+        if k not in slots:
+            dict_[k] = v
+        elif not isinstance(v, types.MemberDescriptorType):
+            sloted_members[k] = v
+    new_cls = type(cls.__name__, cls.__bases__, dict_)
+    for k, v in sloted_members.items():
+        setattr(new_cls, k, v)
+    return new_cls