Added a warning for gluing an object outside of a context

scrapbook/api.py

@@ -20,8 +20,10 @@
 from .scraps import Scrap, scrap_to_payload
 from .schemas import GLUE_PAYLOAD_FMT
 from .encoders import registry as encoder_registry
+from .utils import kernel_required
 
 
+@kernel_required
 def glue(name, scrap, encoder=None, display=None):
     """
     Records a scrap (data value) in the given notebook cell.

scrapbook/models.py

@@ -22,6 +22,7 @@
 from .schemas import GLUE_PAYLOAD_PREFIX, RECORD_PAYLOAD_PREFIX
 from .encoders import registry as encoder_registry
 from .exceptions import ScrapbookException
+from .utils import kernel_required
 
 
 def merge_dicts(dicts):
@@ -252,6 +253,7 @@ def _strip_scrapbook_metadata(self, metadata):
         copied.pop("scrapbook", None)
         return copied
 
+    @kernel_required
     def reglue(self, name, new_name=None, raise_on_missing=True, unattached=False):
         """
         Display output from a named source of the notebook.

scrapbook/tests/test_api.py

@@ -8,10 +8,19 @@
 from IPython.display import Image
 
 from . import get_fixture_path
+from .. import utils
 from ..api import glue
 from ..schemas import GLUE_PAYLOAD_FMT
 
 
+@pytest.fixture(scope='session', autouse=True)
+def kernel_mock():
+    """Mocks the kernel to capture warnings during testing"""
+    with mock.patch.object(utils, 'is_kernel') as _fixture:
+        _fixture.return_value = True
+        yield _fixture
+
+
 @pytest.mark.parametrize(
     "name,scrap,encoder,data,metadata",
     [
@@ -196,3 +205,10 @@ def test_glue_plus_display(
             mock.call(display_output, metadata=display_metadata, raw=True),
         ]
     )
+
+
+@mock.patch("scrapbook.utils.is_kernel")
+def test_glue_warning(kernel_mock):
+    kernel_mock.return_value = False
+    with pytest.warns(UserWarning):
+        glue('foo', 'bar', 'text')

scrapbook/tests/test_notebooks.py

@@ -10,7 +10,7 @@
 from nbformat.v4 import new_notebook, new_code_cell, new_markdown_cell, new_output
 
 from . import get_notebook_path, get_notebook_dir
-from .. import read_notebook
+from .. import read_notebook, utils
 from ..models import Notebook
 from ..exceptions import ScrapbookException
 
@@ -21,6 +21,13 @@
     FileNotFoundError = IOError
 
 
+@pytest.fixture(scope='session', autouse=True)
+def kernel_mock():
+    """Mocks the kernel to capture warnings during testing"""
+    with mock.patch.object(utils, 'is_kernel') as _fixture:
+        yield _fixture
+
+
 class AnyDict(object):
     def __eq__(self, other):
         return isinstance(other, dict)
@@ -298,3 +305,17 @@ def test_metadata_but_empty_content():
 def test_markdown():
     nb = Notebook(new_notebook(cells=[new_markdown_cell("this is a test.")]))
     assert nb.scraps == collections.OrderedDict()
+
+
+@mock.patch("scrapbook.utils.is_kernel")
+def test_reglue_warning(kernel_mock, notebook_result):
+    kernel_mock.return_value = False
+    with pytest.warns(UserWarning):
+        notebook_result.reglue('number')
+
+
+@mock.patch("scrapbook.utils.is_kernel")
+def test_reglue_kernel_no_warning(kernel_mock, notebook_result, recwarn):
+    kernel_mock.return_value = True
+    notebook_result.reglue('number')
+    assert len(recwarn) == 0

scrapbook/tests/test_scrapbooks.py

@@ -11,10 +11,17 @@
 from pandas.util.testing import assert_frame_equal
 
 from . import get_notebook_path
-from .. import read_notebooks
+from .. import read_notebooks, utils
 from ..scraps import Scrap, Scraps
 
 
+@pytest.fixture(scope='session', autouse=True)
+def kernel_mock():
+    """Mocks the kernel to capture warnings during testing"""
+    with mock.patch.object(utils, 'is_kernel') as _fixture:
+        yield _fixture
+
+
 class AnyMarkdownWith(Markdown):
     def __eq__(self, other):
         try:

scrapbook/tests/test_utils.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+import sys
+
+from mock import MagicMock
+from ..utils import is_kernel
+
+
+def test_is_kernel_true():
+    class FakeIPyKernel():
+        kernel = True
+    sys.modules['IPython'] = MagicMock()
+    sys.modules['IPython'].get_ipython.return_value = FakeIPyKernel
+    assert is_kernel()
+    del sys.modules['IPython']
+
+
+def test_not_kernel_in_ipython():
+    sys.modules['IPython'] = MagicMock()
+    sys.modules['IPython'].get_ipython.return_value = {}
+    assert not is_kernel()
+    del sys.modules['IPython']

scrapbook/utils.py

@@ -0,0 +1,33 @@
+# -*- coding: utf-8 -*-
+"""
+utils.py
+
+Provides the utilities for scrapbook functions and operations.
+"""
+import sys
+import warnings
+from functools import wraps
+
+
+def is_kernel():
+    """
+    Returns True if execution context is inside a kernel
+    """
+    # if IPython hasn't been imported, there's nothing to check
+    if 'IPython' in sys.modules:
+        from IPython import get_ipython
+        ipy = get_ipython()
+        if ipy is not None:
+            return getattr(ipy, 'kernel', None) is not None
+    return False
+
+
+def kernel_required(f):
+    @wraps(f)
+    def wrapper(*args, **kwds):
+        if not is_kernel():
+            warnings.warn(
+                "No kernel detected for '{fname}'.".format(
+                    fname=f.__name__))
+        return f(*args, **kwds)
+    return wrapper