Raise error early on unrecognised method + add tests

Author: matt-graham

s2fft/precompute_transforms/spherical.py

@@ -62,6 +62,8 @@ def inverse(
         np.ndarray: Pixel-space coefficients with shape.
 
     """
+    if method not in _inverse_functions:
+        raise ValueError(f"Method {method} not recognised.")
     if reality and spin != 0:
         reality = False
         warn(
@@ -81,8 +83,6 @@ def inverse(
         if kernel is None
         else kernel
     )
-    if method not in _inverse_functions:
-        raise ValueError(f"Method {method} not recognised.")
     return _inverse_functions[method](flm, kernel, **common_kwargs)
 
 
@@ -351,6 +351,8 @@ def forward(
         np.ndarray: Spherical harmonic coefficients.
 
     """
+    if method not in _forward_functions:
+        raise ValueError(f"Method {method} not recognised.")
     if reality and spin != 0:
         reality = False
         warn(
@@ -370,8 +372,6 @@ def forward(
         if kernel is None
         else kernel
     )
-    if method not in _forward_functions:
-        raise ValueError(f"Method {method} not recognised.")
     if iter == 0:
         return _forward_functions[method](f, kernel, **common_kwargs)
     else:

tests/test_spherical_precompute.py

@@ -324,3 +324,19 @@ def test_transform_forward_high_spin(
     flm_recov = forward(f, L, spin, kernel, sampling, reality, "numpy")
     tol = 1e-8 if sampling.lower() in ["dh", "gl"] else 1e-12
     np.testing.assert_allclose(flm_recov, flm, atol=tol, rtol=tol)
+
+
+def test_forward_transform_unrecognised_method_raises():
+    method = "invalid_method"
+    L = 32
+    f = np.zeros(samples.f_shape(L))
+    with pytest.raises(ValueError, match=f"{method} not recognised"):
+        forward(f, L, method=method)
+
+
+def test_inverse_transform_unrecognised_method_raises():
+    method = "invalid_method"
+    L = 32
+    flm = np.zeros(samples.flm_shape(L))
+    with pytest.raises(ValueError, match=f"{method} not recognised"):
+        inverse(flm, L, method=method)