Restrict u.spectral equivalency to contexts where it is required

specutils/spectra/spectral_region.py

@@ -155,9 +155,10 @@ def __delitem__(self, item):
     def _valid(self):
 
         # Lower bound < Upper bound for all sub regions in length physical type
-        sub_regions = [(x[0].to('m'), x[1].to('m'))
-                       if x[0].unit.is_equivalent(u.m) else x
-                       for x in self._subregions]
+        with u.set_enabled_equivalencies(u.spectral()):
+            sub_regions = [(x[0].to('m'), x[1].to('m'))
+                           if x[0].unit.is_equivalent(u.m) else x
+                           for x in self._subregions]
 
         if any(x[0] >= x[1] for x in sub_regions):
             raise ValueError('Lower bound must be strictly less than the upper bound')

specutils/spectra/spectrum1d.py

@@ -15,8 +15,6 @@
 
 __doctest_skip__ = ['Spectrum1D.spectral_resolution']
 
-u.set_enabled_equivalencies(u.spectral())
-
 
 class Spectrum1D(OneDSpectrumMixin, NDDataRef):
     """
@@ -111,8 +109,7 @@ def __init__(self, flux=None, spectral_axis=None, wcs=None,
                              "Assuming units of spectral axis ('%s').",
                              spectral_axis.unit)
                 rest_value = u.Quantity(rest_value, spectral_axis.unit)
-            elif not rest_value.unit.is_equivalent(u.AA) \
-                    and not rest_value.unit.is_equivalent(u.Hz):
+            elif not rest_value.unit.is_equivalent(u.AA, equivalencies=u.spectral()):
                 raise u.UnitsError("Rest value must be "
                                    "energy/wavelength/frequency equivalent.")
 

specutils/tests/test_analysis.py

@@ -51,7 +51,7 @@ def test_equivalent_width():
 
     result = equivalent_width(spectrum)
 
-    assert result.unit.is_equivalent(spectrum.wcs.unit)
+    assert result.unit.is_equivalent(spectrum.wcs.unit, equivalencies=u.spectral())
 
     # Since this is an emission line, we expect the equivalent width value to
     # be negative
@@ -92,7 +92,7 @@ def test_equivalent_width_continuum(continuum):
 
     result = equivalent_width(spectrum, continuum=continuum)
 
-    assert result.unit.is_equivalent(spectrum.wcs.unit)
+    assert result.unit.is_equivalent(spectrum.wcs.unit, equivalencies=u.spectral())
 
     # Since this is an emission line, we expect the equivalent width value to
     # be negative
@@ -116,7 +116,7 @@ def test_equivalent_width_absorption():
 
     result = equivalent_width(spectrum)
 
-    assert result.unit.is_equivalent(spectrum.wcs.unit)
+    assert result.unit.is_equivalent(spectrum.wcs.unit, equivalencies=u.spectral())
 
     expected = amplitude*np.sqrt(2*np.pi) * u.GHz
 

specutils/tests/test_spectrum1d.py

@@ -135,6 +135,17 @@ def test_spectral_axis_conversions():
     new_spec = spec.with_spectral_unit(u.GHz)
 
 
+@pytest.mark.parametrize('unit', ['micron', 'GHz', 'cm**-1', 'eV'])
+def test_spectral_axis_equivalencies(unit):
+    """Test that `u.spectral` equivalencies are enabled for `spectral_axis`."""
+
+    spectral_axis=np.array([3400, 5000, 6660]) * u.AA
+    spec = Spectrum1D(flux=np.array([26.0, 30.0, 44.5]) * u.Jy, spectral_axis=spectral_axis)
+
+    new_axis = spectral_axis.to(unit, equivalencies=u.spectral())
+    assert u.allclose(spec.spectral_axis.to(unit), new_axis)
+
+
 def test_redshift():
     spec = Spectrum1D(flux=np.array([26.0, 30., 44.5]) * u.Jy,
                       spectral_axis=np.array([4000, 6000, 8000]) * u.AA,
@@ -387,3 +398,14 @@ def test_str():
 """Spectrum1D (length=1)
 flux:             [ 1.0 Jy ],  mean=1.0 Jy
 spectral axis:    [ 0.0 nm ],  mean=0.0 nm"""
+
+
+def test_equivalencies():
+    """
+    Test that after import `u.spectral` equivalencies are not enabled in the global namespace.
+    """
+    assert u.micron.is_equivalent(u.cm**-1) is False
+    assert u.micron.is_equivalent(u.Hz) is False
+    assert u.micron.is_equivalent(u.eV) is False
+    assert u.Hz.is_equivalent(u.cm**-1) is False
+    assert u.Hz.is_equivalent(u.eV) is False