Handling file expiration

* Generate a catalog of the expiration dates for files,
* Detect when a file has expired and raise a ``UserWarning``

CHANGELOG.md

@@ -7,6 +7,8 @@
 * Dropped compatibility with Python 3.3 and 3.4, as skyfield did.
 * Added basic tests for the ``get_skyfield_data_path`` function using `tox`.
 * Added automated tests through Travis CI.
+* Generate a catalog of the expiration dates for files,
+* Detect when a file has expired and raise a ``UserWarning``
 
 ## 0.0.2 (2019-08-23)
 

README.md

@@ -55,6 +55,18 @@ If you want to make sure that the data files would **never** be downloaded, you
 load = Loader(get_skyfield_data_path(), expire=False)
 ```
 
+Whenever a file contained in the catalog has expired, you're going to receive a warning when loading the `skyfield-data` path:
+
+```python
+>>> from skyfield_data import get_skyfield_data_path
+>>> from skyfield.api import Loader
+>>> load = Loader(get_skyfield_data_path())
+/home/[redacted]/skyfield_data/expirations.py:25: RuntimeWarning: The file de421.bsp has expired. Please upgrade your version of `skyfield-data` or expect computation errors
+  RuntimeWarning
+```
+
+By default, the loading isn't blocked, but it's strongly recommended to upgrade to a more recent version, to make sure you're not going to make wrong astronomical computations.
+
 ## Developers
 
 We're providing a ``Makefile`` with basic targets to play around with the toolkit. use ``make help`` to get more details.

download.py

@@ -2,17 +2,17 @@
 import argparse
 from datetime import date
 from datetime import datetime, timedelta
-from os.path import join, exists
+from os.path import join, exists, abspath, dirname
 import shutil
 from urllib.request import urlopen
 from jplephem.spk import DAF, SPK
 
-from skyfield_data import get_skyfield_data_path
-
 JPL = "ftp://ssd.jpl.nasa.gov/pub/eph/planets/bsp"
 USNO = "http://maia.usno.navy.mil/ser7"
 IERS = "https://hpiers.obspm.fr/iers/bul/bulc"
 
+__DATA_PATH = abspath(join(dirname(__file__), "skyfield_data", "data"))
+
 
 def calendar_date(jd_integer):
     """Convert Julian Day `jd_integer` into a Gregorian (year, month, day)."""
@@ -188,14 +188,21 @@ def main(args):
             "expiration_func": leap_seconds_expiration
         },
     }
+    # For expiration date content
+    target_expiration = abspath(
+        join(__DATA_PATH, '..', 'expiration_data.py')
+    )
+    expiration_dates = {}
 
     for filename, params in items.items():
         server = params["server"]
         url = "{}/{}".format(server, filename)
-        target = join(get_skyfield_data_path(), filename)
+        target = join(__DATA_PATH, filename)
+
+        expiration_date = get_expiration_date(target, params)
+        expiration_dates[filename] = expiration_date
 
         if args.check_only:
-            expiration_date = get_expiration_date(target, params)
             print(
                 "File: {} => expiration: {}".format(
                     filename, expiration_date or "`unknown`"
@@ -214,6 +221,13 @@ def main(args):
             download(url, target)
         else:
             print("Skipping {} ({})".format(filename, reason))
+    # Generating the expiration date file.
+    expiration_template = """import datetime
+
+EXPIRATIONS = {}
+"""
+    with open(target_expiration, 'w') as fd:
+        fd.write(expiration_template.format(expiration_dates))
     print("\nDone\n")
 
 

skyfield_data/__init__.py

@@ -1,4 +1,5 @@
 from os.path import dirname, join, abspath
+from .expirations import check_expirations
 
 __DATA_PATH = abspath(join(dirname(__file__), "data"))
 
@@ -14,6 +15,7 @@ def get_skyfield_data_path():
         load = Loader(get_skyfield_data_path())
         planets = load('de421.bsp')
     """
+    check_expirations()
     return __DATA_PATH
 
 

skyfield_data/expiration_data.py

@@ -0,0 +1,3 @@
+import datetime
+
+EXPIRATIONS = {'de421.bsp': datetime.date(2053, 10, 8), 'deltat.data': datetime.date(2020, 6, 1), 'deltat.preds': datetime.date(2021, 1, 1), 'Leap_Second.dat': datetime.date(2020, 7, 28)}

skyfield_data/expirations.py

@@ -0,0 +1,26 @@
+import warnings
+from datetime import date
+from os.path import dirname, join, abspath
+from os import listdir
+from .expiration_data import EXPIRATIONS
+
+
+__DATA_PATH = abspath(join(dirname(__file__), "data"))
+
+
+def get_all():
+    return EXPIRATIONS
+
+
+def check_expirations():
+    expirations = get_all()
+    files = listdir(__DATA_PATH)
+    for filename in files:
+        expiration_date = expirations.get(filename)
+        if expiration_date and date.today() >= expiration_date:
+            warnings.warn(
+                ("The file {} has expired."
+                 " Please upgrade your version of `skyfield-data` or expect"
+                 " computation errors").format(filename),
+                RuntimeWarning
+            )

tests/test_expiration_date.py

@@ -0,0 +1,32 @@
+import mock
+from datetime import date
+from datetime import timedelta
+from skyfield_data import get_skyfield_data_path
+
+
+@mock.patch('skyfield_data.expirations.get_all')
+def test_no_expiration(mocked_exp):
+    mocked_exp.return_value = {}
+    with mock.patch('warnings.warn') as mocked_warn:
+        get_skyfield_data_path()
+    assert mocked_warn.call_count == 0
+
+
+@mock.patch('skyfield_data.expirations.get_all')
+def test_expiration_deltat_distant_future(mocked_exp):
+    mocked_exp.return_value = {
+        'deltat.data': date.today() + timedelta(days=10000)
+    }
+    with mock.patch('warnings.warn') as mocked_warn:
+        get_skyfield_data_path()
+    assert mocked_warn.call_count == 0
+
+
+@mock.patch('skyfield_data.expirations.get_all')
+def test_expiration_deltat_yesterday(mocked_exp):
+    mocked_exp.return_value = {
+        'deltat.data': date.today() - timedelta(days=1)
+    }
+    with mock.patch('warnings.warn') as mocked_warn:
+        get_skyfield_data_path()
+    assert mocked_warn.call_count == 1

tox.ini

@@ -4,7 +4,7 @@ envlist = py27,py35,py36,py37
 
 [testenv]
 commands =
-    pytest -s
+    pytest -s {posargs}
 deps =
     .[tests]