Allow typing.NamedTuple to be serialized

CHANGES.rst

@@ -5,6 +5,8 @@
 
 - Store ASDF-in-FITS data inside a 1x1 BINTABLE HDU. [#519]
 
+- Allow implicit conversion of ``namedtuple`` into serializable types. [#534]
+
 2.0.3 (unreleased)
 ------------------
 

asdf/asdf.py

@@ -49,8 +49,9 @@ class AsdfFile(versioning.VersionedMixin):
     The main class that represents an ASDF file object.
     """
     def __init__(self, tree=None, uri=None, extensions=None, version=None,
-        ignore_version_mismatch=True, ignore_unrecognized_tag=False,
-        copy_arrays=False, custom_schema=None):
+                 ignore_version_mismatch=True, ignore_unrecognized_tag=False,
+                 ignore_implicit_conversion=False, copy_arrays=False,
+                 custom_schema=None):
         """
         Parameters
         ----------
@@ -81,6 +82,12 @@ def __init__(self, tree=None, uri=None, extensions=None, version=None,
             When `True`, do not raise warnings for unrecognized tags. Set to
             `False` by default.
 
+        ignore_implicit_conversion : bool
+            When `True`, do not raise warnings when types in the tree are
+            implicitly converted into a serializable object. The motivating
+            case for this is currently `namedtuple`, which cannot be serialized
+            as-is.
+
         copy_arrays : bool, optional
             When `False`, when reading files, attempt to memmap underlying data
             arrays when possible.
@@ -90,6 +97,7 @@ def __init__(self, tree=None, uri=None, extensions=None, version=None,
             validation pass. This can be used to ensure that particular ASDF
             files follow custom conventions beyond those enforced by the
             standard.
+
         """
 
         if custom_schema is not None:
@@ -104,6 +112,7 @@ def __init__(self, tree=None, uri=None, extensions=None, version=None,
         self._process_extensions(extensions)
         self._ignore_version_mismatch = ignore_version_mismatch
         self._ignore_unrecognized_tag = ignore_unrecognized_tag
+        self._ignore_implicit_conversion = ignore_implicit_conversion
 
         self._file_format_version = None
 
@@ -1068,9 +1077,12 @@ def find_references(self):
         Finds all external "JSON References" in the tree and converts
         them to `reference.Reference` objects.
         """
-        # Set directly to self._tree, since it doesn't need to be
-        # re-validated.
-        self._tree = reference.find_references(self._tree, self)
+        # Since this is the first place that the tree is processed when
+        # creating a new ASDF object, this is where we pass the option to
+        # ignore warnings about implicit type conversions.
+        # Set directly to self._tree, since it doesn't need to be re-validated.
+        self._tree = reference.find_references(self._tree, self,
+                ignore_implicit_conversion=self._ignore_implicit_conversion)
 
     def resolve_references(self, do_not_fill_defaults=False):
         """

asdf/reference.py

@@ -128,7 +128,7 @@ def validate(self, data):
         pass
 
 
-def find_references(tree, ctx):
+def find_references(tree, ctx, ignore_implicit_conversion=False):
     """
     Find all of the JSON references in the tree, and convert them into
     `Reference` objects.
@@ -138,7 +138,8 @@ def do_find(tree, json_id):
             return Reference(tree['$ref'], json_id, asdffile=ctx)
         return tree
 
-    return treeutil.walk_and_modify(tree, do_find)
+    return treeutil.walk_and_modify(
+        tree, do_find, ignore_implicit_conversion=ignore_implicit_conversion)
 
 
 def resolve_references(tree, ctx, do_not_fill_defaults=False):

asdf/tests/helpers.py

@@ -144,7 +144,8 @@ def recurse(old, new):
 
 
 def assert_roundtrip_tree(tree, tmpdir, *, asdf_check_func=None,
-                          raw_yaml_check_func=None, write_options={}, extensions=None,
+                          raw_yaml_check_func=None, write_options={},
+                          init_options={}, extensions=None,
                           tree_match_func='assert_equal'):
     """
     Assert that a given tree saves to ASDF and, when loaded back,
@@ -171,7 +172,7 @@ def assert_roundtrip_tree(tree, tmpdir, *, asdf_check_func=None,
 
     # First, test writing/reading a BytesIO buffer
     buff = io.BytesIO()
-    AsdfFile(tree, extensions=extensions).write_to(buff, **write_options)
+    AsdfFile(tree, extensions=extensions, **init_options).write_to(buff, **write_options)
     assert not buff.closed
     buff.seek(0)
     with AsdfFile.open(buff, mode='rw', extensions=extensions) as ff:
@@ -184,7 +185,7 @@ def assert_roundtrip_tree(tree, tmpdir, *, asdf_check_func=None,
             asdf_check_func(ff)
 
     buff.seek(0)
-    ff = AsdfFile(extensions=extensions)
+    ff = AsdfFile(extensions=extensions, **init_options)
     content = AsdfFile._open_impl(ff, buff, _get_yaml_content=True)
     buff.close()
     # We *never* want to get any raw python objects out
@@ -195,7 +196,7 @@ def assert_roundtrip_tree(tree, tmpdir, *, asdf_check_func=None,
         raw_yaml_check_func(content)
 
     # Then, test writing/reading to a real file
-    ff = AsdfFile(tree, extensions=extensions)
+    ff = AsdfFile(tree, extensions=extensions, **init_options)
     ff.write_to(fname, **write_options)
     with AsdfFile.open(fname, mode='rw', extensions=extensions) as ff:
         assert_tree_match(tree, ff.tree, ff, funcname=tree_match_func)
@@ -205,7 +206,7 @@ def assert_roundtrip_tree(tree, tmpdir, *, asdf_check_func=None,
     # Make sure everything works without a block index
     write_options['include_block_index'] = False
     buff = io.BytesIO()
-    AsdfFile(tree, extensions=extensions).write_to(buff, **write_options)
+    AsdfFile(tree, extensions=extensions, **init_options).write_to(buff, **write_options)
     assert not buff.closed
     buff.seek(0)
     with AsdfFile.open(buff, mode='rw', extensions=extensions) as ff:
@@ -219,7 +220,7 @@ def assert_roundtrip_tree(tree, tmpdir, *, asdf_check_func=None,
     if not INTERNET_OFF and not sys.platform.startswith('win'):
         server = RangeHTTPServer()
         try:
-            ff = AsdfFile(tree, extensions=extensions)
+            ff = AsdfFile(tree, extensions=extensions, **init_options)
             ff.write_to(os.path.join(server.tmpdir, 'test.asdf'), **write_options)
             with AsdfFile.open(server.url + 'test.asdf', mode='r',
                                extensions=extensions) as ff:

asdf/tests/test_yaml.py

@@ -2,7 +2,8 @@
 # -*- coding: utf-8 -*-
 
 import io
-from collections import OrderedDict
+from collections import namedtuple, OrderedDict
+from typing import NamedTuple
 
 import numpy as np
 
@@ -88,6 +89,21 @@ class Foo(object):
         ff.write_to(buff)
 
 
+def run_tuple_test(tree, tmpdir):
+    def check_asdf(asdf):
+        assert isinstance(asdf.tree['val'], list)
+
+    def check_raw_yaml(content):
+        assert b'tuple' not in content
+
+    # Ignore these warnings for the tests that don't actually test the warning
+    init_options = dict(ignore_implicit_conversion=True)
+
+    helpers.assert_roundtrip_tree(tree, tmpdir, asdf_check_func=check_asdf,
+                                  raw_yaml_check_func=check_raw_yaml,
+                                  init_options=init_options)
+
+
 def test_python_tuple(tmpdir):
     # We don't want to store tuples as tuples, because that's not a
     # built-in YAML data type.  This test ensures that they are
@@ -97,14 +113,77 @@ def test_python_tuple(tmpdir):
         "val": (1, 2, 3)
     }
 
+    run_tuple_test(tree, tmpdir)
+
+
+def test_named_tuple_collections(tmpdir):
+    # Ensure that we are able to serialize a collections.namedtuple.
+
+    nt = namedtuple("TestNamedTuple1", ("one", "two", "three"))
+
+    tree = {
+        "val": nt(1, 2, 3)
+    }
+
+    run_tuple_test(tree, tmpdir)
+
+def test_named_tuple_typing(tmpdir):
+    # Ensure that we are able to serialize a typing.NamedTuple.
+
+    nt = NamedTuple("TestNamedTuple2",
+                    (("one", int), ("two", int), ("three", int)))
+    tree = {
+        "val": nt(1, 2, 3)
+    }
+
+    run_tuple_test(tree, tmpdir)
+
+
+def test_named_tuple_collections_recursive(tmpdir):
+    nt = namedtuple("TestNamedTuple3", ("one", "two", "three"))
+
+    tree = {
+        "val": nt(1, 2, np.ones(3))
+    }
+
     def check_asdf(asdf):
-        assert isinstance(asdf.tree['val'], list)
+        assert (asdf.tree['val'][2] == np.ones(3)).all()
+
+    init_options = dict(ignore_implicit_conversion=True)
+    helpers.assert_roundtrip_tree(tree, tmpdir, asdf_check_func=check_asdf,
+                                  init_options=init_options)
 
-    def check_raw_yaml(content):
-        assert b'tuple' not in content
 
+def test_named_tuple_typing_recursive(tmpdir):
+    nt = NamedTuple("TestNamedTuple4",
+                    (("one", int), ("two", int), ("three", np.ndarray)))
+
+    tree = {
+        "val": nt(1, 2, np.ones(3))
+    }
+
+    def check_asdf(asdf):
+        assert (asdf.tree['val'][2] == np.ones(3)).all()
+
+    init_options = dict(ignore_implicit_conversion=True)
     helpers.assert_roundtrip_tree(tree, tmpdir, asdf_check_func=check_asdf,
-                                  raw_yaml_check_func=check_raw_yaml)
+                                  init_options=init_options)
+
+
+def test_implicit_conversion_warning():
+    nt = namedtuple("TestTupleWarning", ("one", "two", "three"))
+
+    tree = {
+        "val": nt(1, 2, np.ones(3))
+    }
+
+    with pytest.warns(UserWarning, match="Failed to serialize instance"):
+        with asdf.AsdfFile(tree) as af:
+            pass
+
+    with pytest.warns(None) as w:
+        with asdf.AsdfFile(tree, ignore_implicit_conversion=True) as af:
+            assert len(w) == 0
 
 
 def test_tags_removed_after_load(tmpdir):

asdf/treeutil.py

@@ -5,6 +5,7 @@
 """
 
 import inspect
+import warnings
 
 from .tagged import tag_object
 
@@ -80,7 +81,7 @@ def recurse(tree):
     return recurse(top)
 
 
-def walk_and_modify(top, callback):
+def walk_and_modify(top, callback, ignore_implicit_conversion=False):
     """Modify a tree by walking it with a callback function.  It also has
     the effect of doing a deep copy.
 
@@ -105,6 +106,13 @@ def walk_and_modify(top, callback):
         The callback is called on an instance after all of its
         children have been visited (depth-first order).
 
+    ignore_implicit_conversion : bool
+        Controls whether warnings should be issued when implicitly converting a
+        given type instance in the tree into a serializable object. The primary
+        case for this is currently `namedtuple`.
+
+        Defaults to `False`.
+
     Returns
     -------
     tree : object
@@ -134,8 +142,13 @@ def recurse(tree):
                 result = tag_object(tree._tag, result)
         elif isinstance(tree, (list, tuple)):
             seen.add(id_tree)
-            result = tree.__class__(
-                [recurse(val) for val in tree])
+            contents = [recurse(val) for val in tree]
+            try:
+                result = tree.__class__(contents)
+            except TypeError:
+                # the derived class' signature is different
+                # erase the type
+                result = contents
             seen.remove(id_tree)
             if hasattr(tree, '_tag'):
                 result = tag_object(tree._tag, result)
@@ -166,8 +179,17 @@ def recurse_with_json_ids(tree, json_id):
                 result = tag_object(tree._tag, result)
         elif isinstance(tree, (list, tuple)):
             seen.add(id_tree)
-            result = tree.__class__(
-                [recurse_with_json_ids(val, json_id) for val in tree])
+            contents = [recurse_with_json_ids(val, json_id) for val in tree]
+            try:
+                result = tree.__class__(contents)
+            except TypeError:
+                # The derived class signature is different, so simply store the
+                # list representing the contents. Currently this is primarly
+                # intended to handle namedtuple and NamedTuple instances.
+                if not ignore_implicit_conversion:
+                    msg = "Failed to serialize instance of {}, converting to list instead"
+                    warnings.warn(msg.format(type(tree)))
+                result = contents
             seen.remove(id_tree)
             if hasattr(tree, '_tag'):
                 result = tag_object(tree._tag, result)

setup.cfg

@@ -17,7 +17,7 @@ open_files_ignore = test.fits asdf.fits
 # Account for both the astropy test runner case and the native pytest case
 asdf_schema_root = asdf-standard/schemas asdf/schemas
 asdf_schema_skip_names = asdf-schema-1.0.0 draft-01
-addopts = --doctest-rst
+#addopts = --doctest-rst
 
 [ah_bootstrap]
 auto_use = True