Better error message in case of a non GRIB file. Closes #34 for real.

ecmwf · Nov 30, 2018 · 9389835 · 9389835
1 parent 88b5269
commit 9389835
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diff --git a/cfgrib/messages.py b/cfgrib/messages.py
@@ -207,10 +207,14 @@ class FileStream(collections.Iterable):
     def __iter__(self):
         # type: () -> T.Generator[Message, None, None]
         with open(self.path, 'rb') as file:
+            valid_grib_message_found = False
             while True:
                 try:
                     yield self.message_from_file(file, errors=self.errors)
+                    valid_grib_message_found = True
                 except EOFError:
+                    if not valid_grib_message_found:
+                        raise EOFError("No valid GRIB message found in file: %r" % self.path)
                     break
                 except Exception:
                     if self.errors == 'ignore':

diff --git a/tests/test_20_messages.py b/tests/test_20_messages.py
@@ -207,3 +207,8 @@ def test_FileStream():
     assert len(leader) > 100
     assert sum(1 for _ in res) == leader['count']
     assert len(res.index(['paramId'])) == 1
+
+    # __file__ is not a GRIB, but contains the "GRIB" string, so it is a very tricky corner case
+    res = messages.FileStream(str(__file__))
+    with pytest.raises(EOFError):
+        res.first()