fix: use constants to help avoid bugs

Author: beckermr

CHANGES.md

@@ -4,6 +4,12 @@
 
 Changes
 
+- Added support for `rsfitsio` as a backend in addition to `cfitsio`.
+- Added function `fitsio_backend` to return the current backend.
+- Renamed `cfitsio_*` functions to `backend_*` functions for clarity.
+- Added constant `CFITSIO_BACKEND` and `RSFITSIO_BACKEND` which are
+  the return values of `fitsio_backend`.
+
 Bug Fixes
 
 - Added missing memory allocation checks in C layer.

fitsio/__init__.py

@@ -55,4 +55,9 @@
 backend_has_curl_support = cfitsio_has_curl_support
 backend_is_reentrant = cfitsio_is_reentrant
 
+# return values of fitsio_backend, here to help make code
+# clearer and avoid mispelling errors in testing strings
+CFITSIO_BACKEND = "cfitsio"
+RSFITSIO_BACKEND = "rsfitsio"
+
 from .fits_exceptions import FITSFormatError

fitsio/tests/makedata.py

@@ -2,7 +2,12 @@
 import numpy as np
 from functools import lru_cache
 
-from .. import backend_version, fitsio_backend
+from .. import (
+    backend_version,
+    fitsio_backend,
+    CFITSIO_BACKEND,
+    RSFITSIO_BACKEND,
+)
 
 BACKEND_VERSION = backend_version(asfloat=True)
 
@@ -66,8 +71,8 @@ def make_data():
     ]
 
     if (
-        fitsio_backend() == "cfitsio" and BACKEND_VERSION > 4
-    ) or fitsio_backend() == "rsfitsio":
+        fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION > 4
+    ) or fitsio_backend() == RSFITSIO_BACKEND:
         dtype += [
             ('u8scalar', 'u8'),
             ('u8vec', 'u8', nvec),
@@ -78,8 +83,8 @@ def make_data():
     # handle non-space padded strings
     # properly
     if (
-        fitsio_backend() == "cfitsio" and BACKEND_VERSION > 4
-    ) or fitsio_backend() == "rsfitsio":
+        fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION > 4
+    ) or fitsio_backend() == RSFITSIO_BACKEND:
         dtype += [
             ('Sscalar_nopad', Sdtype),
             ('Svec_nopad', Sdtype, nvec),
@@ -97,8 +102,8 @@ def make_data():
         # handle non-space padded strings
         # properly
         if (
-            fitsio_backend() == "cfitsio" and BACKEND_VERSION > 4
-        ) or fitsio_backend() == "rsfitsio":
+            fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION > 4
+        ) or fitsio_backend() == RSFITSIO_BACKEND:
             dtype += [
                 ('Uscalar_nopad', Udtype),
                 ('Uvec_nopad', Udtype, nvec),
@@ -128,8 +133,8 @@ def make_data():
         'c16',
     ]
     if (
-        fitsio_backend() == "cfitsio" and BACKEND_VERSION > 4
-    ) or fitsio_backend() == "rsfitsio":
+        fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION > 4
+    ) or fitsio_backend() == RSFITSIO_BACKEND:
         dtypes += ["u8"]
 
     for t in dtypes:
@@ -184,8 +189,8 @@ def make_data():
     # handle non-space padded strings
     # properly
     if (
-        fitsio_backend() == "cfitsio" and BACKEND_VERSION > 4
-    ) or fitsio_backend() == "rsfitsio":
+        fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION > 4
+    ) or fitsio_backend() == RSFITSIO_BACKEND:
         data['Sscalar_nopad'] = ['hello', 'world', 'good', 'bye']
         data['Svec_nopad'][:, 0] = 'hello'
         data['Svec_nopad'][:, 1] = 'world'
@@ -209,8 +214,8 @@ def make_data():
         # handle non-space padded strings
         # properly
         if (
-            fitsio_backend() == "cfitsio" and BACKEND_VERSION > 4
-        ) or fitsio_backend() == "rsfitsio":
+            fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION > 4
+        ) or fitsio_backend() == RSFITSIO_BACKEND:
             data['Uscalar_nopad'] = ['hello', 'world', 'good', 'bye']
             data['Uvec_nopad'][:, 0] = 'hello'
             data['Uvec_nopad'][:, 1] = 'world'
@@ -356,8 +361,8 @@ def make_data():
         ('Sarr', Sdtype, ashape),
     ]
     if (
-        fitsio_backend() == "cfitsio" and BACKEND_VERSION > 4
-    ) or fitsio_backend() == "rsfitsio":
+        fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION > 4
+    ) or fitsio_backend() == RSFITSIO_BACKEND:
         dtype += [
             ('u8vec', 'u8', nvec),
             ('u8arr', 'u8', ashape),
@@ -377,8 +382,8 @@ def make_data():
 
     _dtypes = ['u1', 'i1', 'u2', 'i2', 'u4', 'i4', 'i8', 'f4', 'f8']
     if (
-        fitsio_backend() == "cfitsio" and BACKEND_VERSION > 4
-    ) or fitsio_backend() == "rsfitsio":
+        fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION > 4
+    ) or fitsio_backend() == RSFITSIO_BACKEND:
         _dtypes += ["u8"]
     for t in _dtypes:
         vardata[t + 'scalar'] = 1 + np.arange(nrows, dtype=t)

fitsio/tests/test_header.py

@@ -10,7 +10,12 @@
 from ..fitslib import FITS, read_header, write
 from ..header import FITSHDR
 from ..hdu.base import INVALID_HDR_CHARS
-from .. import backend_version, fitsio_backend
+from .. import (
+    backend_version,
+    fitsio_backend,
+    CFITSIO_BACKEND,
+    RSFITSIO_BACKEND,
+)
 
 BACKEND_VERSION = backend_version(asfloat=True)
 
@@ -107,8 +112,8 @@ def test_header_write_read():
                 'longs': lorem_ipsum,
             }
             if (
-                fitsio_backend() == "cfitsio" and BACKEND_VERSION > 4.02
-            ) or fitsio_backend() == "rsfitsio":
+                fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION > 4.02
+            ) or fitsio_backend() == RSFITSIO_BACKEND:
                 # force hierarch + continue
                 header["long_keyword_name"] = lorem_ipsum
 

fitsio/tests/test_image.py

@@ -5,15 +5,21 @@
 
 # import warnings
 from .checks import check_header, compare_array
-from .. import backend_version, backend_is_bundled, fitsio_backend
+from .. import (
+    backend_version,
+    backend_is_bundled,
+    fitsio_backend,
+    CFITSIO_BACKEND,
+    RSFITSIO_BACKEND,
+)
 import numpy as np
 from ..fitslib import FITS
 
 BACKEND_VERSION = backend_version(asfloat=True)
 DTYPES = ['u1', 'i1', 'u2', 'i2', '<u4', 'i4', 'i8', '>f4', 'f8']
 if (
-    BACKEND_VERSION > 3.44 and fitsio_backend() == "cfitsio"
-) or fitsio_backend() == "rsfitsio":
+    BACKEND_VERSION > 3.44 and fitsio_backend() == CFITSIO_BACKEND
+) or fitsio_backend() == RSFITSIO_BACKEND:
     DTYPES += ["u8"]
 
 
@@ -77,7 +83,7 @@ def test_image_write_read_unaligned(dtype, with_nan):
     """
 
     if (dtype == ">f4" or ("f" in dtype and with_nan)) and (
-        fitsio_backend() == "cfitsio" and not backend_is_bundled()
+        fitsio_backend() == CFITSIO_BACKEND and not backend_is_bundled()
     ):
         pytest.xfail(
             reason=(
@@ -563,7 +569,7 @@ def test_image_write_subset_2d(
         with_nan
         and with_nan_base_img
         and partial_overlap_str in partial_overlap_str_cases
-        and (fitsio_backend() == "cfitsio" and not backend_is_bundled())
+        and (fitsio_backend() == CFITSIO_BACKEND and not backend_is_bundled())
         and compress_kws
         and compress_kws.get("qlevel", 0) > 0
     ):
@@ -787,7 +793,7 @@ def test_image_read_write_ulonglong():
         with FITS(fname, 'rw') as fits:
             data = np.arange(5 * 20, dtype='u8').reshape(5, 20)
             header = {'DTYPE': 'u8', 'NBYTES': data.dtype.itemsize}
-            if BACKEND_VERSION < 3.45 and fitsio_backend() == "cfitsio":
+            if BACKEND_VERSION < 3.45 and fitsio_backend() == CFITSIO_BACKEND:
                 with pytest.raises(TypeError) as e:
                     fits.write_image(data, header=header)
                 assert (
@@ -804,7 +810,7 @@ def test_image_read_write_ulonglong():
                 check_header(header, rh)
 
         if (
-            BACKEND_VERSION >= 3.45 and fitsio_backend() == "cfitsio"
-        ) or fitsio_backend() == "rsfitsio":
+            BACKEND_VERSION >= 3.45 and fitsio_backend() == CFITSIO_BACKEND
+        ) or fitsio_backend() == RSFITSIO_BACKEND:
             with FITS(fname) as fits:
                 assert not fits[0].is_compressed(), 'not compressed'

fitsio/tests/test_image_compression.py

@@ -16,7 +16,7 @@
     SUBTRACTIVE_DITHER_1,
 )
 from .. import backend_is_bundled, backend_version
-from .. import fitsio_backend
+from .. import fitsio_backend, CFITSIO_BACKEND
 
 BACKEND_VERSION = backend_version(asfloat=True)
 
@@ -125,7 +125,7 @@ def test_compressed_write_read_fitsobj(compress, dtype, with_nan):
     if (
         "gzip" in compress
         and dtype in ["u2", "i2", "u4", "i4"]
-        and (fitsio_backend() == "cfitsio" and not backend_is_bundled())
+        and (fitsio_backend() == CFITSIO_BACKEND and not backend_is_bundled())
     ):
         pytest.xfail(
             reason=(
@@ -202,7 +202,7 @@ def test_compressed_write_read_fitsobj(compress, dtype, with_nan):
 
 @pytest.mark.skipif(sys.version_info < (3, 9), reason='importlib bug in 3.8')
 @pytest.mark.skipif(
-    BACKEND_VERSION < 3.49 and fitsio_backend() == "cfitsio",
+    BACKEND_VERSION < 3.49 and fitsio_backend() == CFITSIO_BACKEND,
     reason='bug in cfitsio < 3.49',
 )
 def test_gzip_tile_compressed_read_lossless_astropy():
@@ -535,7 +535,7 @@ def test_image_compression_raises_on_python_set(kw, val, set_val_to_none):
 )
 @pytest.mark.parametrize("fname", ["mem://", "test.fits"])
 def test_image_compression_inmem_lossess_int(compress, dtype, fname):
-    if fitsio_backend() == "cfitsio" and not backend_is_bundled():
+    if fitsio_backend() == CFITSIO_BACKEND and not backend_is_bundled():
         pytest.xfail(
             reason=(
                 "Non-bundled cfitsio libraries have a bug. "
@@ -629,8 +629,8 @@ def test_image_mem_reopen_noop():
             marks=[
                 pytest.mark.xfail(
                     condition=BACKEND_VERSION < 4.04
-                    and fitsio_backend() == "cfitsio"
-                    and fitsio_backend() == "cfitsio",
+                    and fitsio_backend() == CFITSIO_BACKEND
+                    and fitsio_backend() == CFITSIO_BACKEND,
                     reason=(
                         "Writing compressed binary tables exceeding "
                         "2**32 bytes fails for cfitsio < 4.04!"
@@ -801,7 +801,10 @@ def test_image_compression_nulls_patches_with_subnormal(
                 # however, on read, we send nullcheck=NAN and as a side
                 # effect the subnormal float value in this row gets truncated
                 # to zero
-                if fitsio_backend() == "cfitsio" and not backend_is_bundled():
+                if (
+                    fitsio_backend() == CFITSIO_BACKEND
+                    and not backend_is_bundled()
+                ):
                     np.testing.assert_array_equal(read_data[1, 1:], 0.0)
                     np.testing.assert_array_equal(read_slice1[1:], 0.0)
 
@@ -853,7 +856,9 @@ def test_image_compression_read_chunks():
 
 
 @pytest.mark.xfail(
-    condition=(fitsio_backend() == "cfitsio" and not backend_is_bundled()),
+    condition=(
+        fitsio_backend() == CFITSIO_BACKEND and not backend_is_bundled()
+    ),
     reason=(
         "system cfitsio must be compiled without FMA instructions to "
         "enable reproducible lossy float compression"
@@ -886,7 +891,9 @@ def test_image_compression_write_read_comp_to_osx_arm64():
 
 
 @pytest.mark.xfail(
-    condition=(fitsio_backend() == "cfitsio" and not backend_is_bundled()),
+    condition=(
+        fitsio_backend() == CFITSIO_BACKEND and not backend_is_bundled()
+    ),
     reason=(
         "system cfitsio must be compiled without FMA instructions to "
         "enable reproducible lossy float compression"
@@ -926,7 +933,7 @@ def test_image_compression_gzip_subnormal_cast_to_zero():
             )
 
         back = read(fn)
-        if fitsio_backend() == "cfitsio" and backend_is_bundled():
+        if fitsio_backend() == CFITSIO_BACKEND and backend_is_bundled():
             assert not back.ravel()[0] == 0, back.ravel()
         else:
             assert back.ravel()[0] == 0, back.ravel()

fitsio/tests/test_segfault.py

@@ -4,7 +4,7 @@
 import numpy as np
 
 import fitsio
-from .. import fitsio_backend, backend_is_bundled
+from .. import fitsio_backend, backend_is_bundled, CFITSIO_BACKEND
 
 import pytest
 
@@ -54,7 +54,7 @@ def _run_mixed(n):
 
 @pytest.mark.slow
 @pytest.mark.skipif(
-    (fitsio_backend() == "cfitsio" and not backend_is_bundled()),
+    (fitsio_backend() == CFITSIO_BACKEND and not backend_is_bundled()),
     reason=(
         "small images cause a memory corruption w/ PLIO "
         "compression (see https://github.com/heasarc/cfitsio/issues/136)"

fitsio/tests/test_table.py

@@ -15,13 +15,19 @@
 from .makedata import make_data
 from ..fitslib import FITS, write, read
 from .. import util
-from .. import backend_has_bzip2_support, fitsio_backend, backend_version
+from .. import (
+    backend_has_bzip2_support,
+    fitsio_backend,
+    backend_version,
+    CFITSIO_BACKEND,
+    RSFITSIO_BACKEND,
+)
 
 BACKEND_VERSION = backend_version(asfloat=True)
 DTYPES = ['u1', 'i1', 'u2', 'i2', '<u4', 'i4', 'i8', '>f4', 'f8']
 if (
-    BACKEND_VERSION > 4 and fitsio_backend() == "cfitsio"
-) or fitsio_backend() == "rsfitsio":
+    BACKEND_VERSION > 4 and fitsio_backend() == CFITSIO_BACKEND
+) or fitsio_backend() == RSFITSIO_BACKEND:
     DTYPES += ["u8"]
 
 
@@ -572,9 +578,9 @@ def test_ascii_table_write_read():
     Test write and read for an ascii table
     """
 
-    if fitsio_backend() == "rsfitsio":
+    if fitsio_backend() == RSFITSIO_BACKEND:
         tol = 1e-14
-    elif fitsio_backend() == "cfitsio":
+    elif fitsio_backend() == CFITSIO_BACKEND:
         tol = 2.15e-16
     else:
         assert False, "No valid backend specified! got " + fitsio_backend()
@@ -899,8 +905,8 @@ def test_table_resize():
         add_data['u4vec'] = 2**31
         add_data['u4arr'] = 2**31
         if (
-            BACKEND_VERSION > 4 and fitsio_backend() == "cfitsio"
-        ) or fitsio_backend() == "rsfitsio":
+            BACKEND_VERSION > 4 and fitsio_backend() == CFITSIO_BACKEND
+        ) or fitsio_backend() == RSFITSIO_BACKEND:
             add_data['u8scalar'] = 2**63
             add_data['u8vec'] = 2**63
             add_data['u8arr'] = 2**63
@@ -1583,7 +1589,7 @@ def test_table_big_col(table_type):
         # v3 cfitsio that is not bundled fails for big
         # columns
         if table_type == "ascii" or (
-            fitsio_backend() == "cfitsio" and BACKEND_VERSION < 4
+            fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION < 4
         ):
             with pytest.raises(OSError) as e:
                 write(pth, d, table_type=table_type)
@@ -1600,7 +1606,7 @@ def test_table_big_col(table_type):
 
 
 @pytest.mark.xfail(
-    condition=fitsio_backend() == "cfitsio" and BACKEND_VERSION < 4,
+    condition=fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION < 4,
     reason=(
         "cfitsio versions < 4 do not easily support null-terminated strings"
     ),
@@ -1631,7 +1637,7 @@ def test_table_read_write_ulonglong():
         fname = os.path.join(tmpdir, 'test.fits')
 
         with FITS(fname, 'rw') as fits:
-            if fitsio_backend() == "cfitsio" and BACKEND_VERSION < 3.45:
+            if fitsio_backend() == CFITSIO_BACKEND and BACKEND_VERSION < 3.45:
                 with pytest.raises(IOError) as e:
                     fits.write_table(
                         adata,