Oracle test failure: Inspecting NullBooleanField

[Shai Berger]

======================================================================
FAIL: test_number_field_types (inspectdb.tests.InspectDBTestCase)
Test introspection of various Django field types
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Traceback (most recent call last):
  File "<.../tests/inspectdb/tests.py",> line 95, in test_number_field_types
    assertFieldType('null_bool_field', "models.BooleanField()")
  File "<.../tests/inspectdb/tests.py",> line 38, in assertFieldType
    self.assertEqual(definition, out_def)
AssertionError: u'models.BooleanField()' != 'models.NullBooleanField()'

----------------------------------------------------------------------
Ran 7008 tests in 11909.588s

FAILED (failures=1, skipped=333, expected failures=8)

The copied report was on master, but 1.7 has it too.
It's probably some minor thing, I'll deal with it later today.

[Shai Berger]

This was introduced by a03d38ddd43957a402b64caddf74a73df72140fb and 5c95a55330bc2531405700a399bfb555bfe80120 on master (342b25449d800ce29ae56ff8285869cbc3133a75 and 1238f92c649ccd4ba99da0ce70be7597c90515d4 on stable/1.7.x). The first commit in each pair introduces a can_introspect_null database-feature, and sets it to False for Oracle; the latter uses the flag in tests for integer and boolean fields.

Oracle has issues introspecting nullability in character fields, because it interprets_empty_strings_as_nulls (so the backend defines all character fields as nullable in order to allow empty strings); but it has no such issues with integer fields or boolean fields.

Unless the can_introspect_null flag serves some 3rd-party backend, I suggest that we simply revert these four commits.

[Shai Berger]

@aaugustin and @manfre have ​confirmed that the flag is needed by django-pymssql, a 3rd-party backend. So, I'm just fixing the Oracle issue.

[Shai Berger <shai@…>]

In 612290400f79fb2293a6a0b0cfa5743ab0cef6b1:

Fixed #22816 -- Corrected Oracle feature flag and fixed introspection test

[Shai Berger <shai@…>]

In 4b922b809413eb9e9d59be0c3b41d0cedefbeb29:

[1.7.x] Fixed #22816 -- Corrected Oracle feature flag and fixed introspection test

Backport of 6122904 from master