Further improve unknown projection error message

proplot/axes/__init__.py

@@ -27,9 +27,14 @@
 # Register projections with package prefix to avoid conflicts
 # NOTE: We integrate with cartopy and basemap rather than using matplotlib's
 # native projection system. Therefore axes names are not part of public API.
-CLASSES = {}  # track valid names
-for _cls in (CartesianAxes, PolarAxes, _BasemapAxes, _CartopyAxes, ThreeAxes):
+_cls_dict = {}  # track valid names
+for _cls in (CartesianAxes, PolarAxes, _CartopyAxes, _BasemapAxes, ThreeAxes):
     for _name in (_cls._name, *_cls._name_aliases):
         with context._state_context(_cls, name='proplot_' + _name):
             mproj.register_projection(_cls)
-            CLASSES[_name] = _cls
+            _cls_dict[_name] = _cls
+_cls_table = '\n'.join(
+    ' ' + key + ' ' * (max(map(len, _cls_dict)) - len(key) + 7)
+    + ('GeoAxes' if cls.__name__[:1] == '_' else cls.__name__)
+    for key, cls in _cls_dict.items()
+)

proplot/axes/geo.py

@@ -406,20 +406,20 @@ def __init__(self, *args, **kwargs):
         *args
             Passed to `matplotlib.axes.Axes`.
         autoextent : bool, optional
-            *For cartopy axes only*. Whether to automatically adjust map bounds based
-            on plotted content or enforce a global map extent (or a map bounded at the
-            equator for polar projections). The extent can subsequently by adjusted
-            with the `~GeoAxes.format` keywords `lonlim`, `latlim`, and `boundinglat`,
-            or with `~cartopy.mpl.geoaxes.GeoAxes.set_extent`.
+            *For cartopy axes only*. Whether to automatically adjust map bounds
+            based on plotted content or enforce a global map extent (or a map bounded
+            at the equator for polar projections). The extent can subsequently by
+            adjusted with the `~GeoAxes.format` keywords `lonlim`, `latlim`, and
+            `boundinglat`, or with `~cartopy.mpl.geoaxes.GeoAxes.set_extent`.
             Default is :rc:`cartopy.autoextent`.
         circular : bool, optional
             *For cartopy axes only*. Whether to bound polar projections with circles
             rather than squares. Note that outer gridline labels cannot be added to
             circularly bounded polar projections. Default is :rc:`cartopy.circular`.
-        map_projection : `~mpl_toolkits.basemap.Basemap` or `~cartopy.crs.Projection`
-            The cartopy or basemap projection instance. This is passed automatically
-            when calling axes-creation commands
-            like `~proplot.figure.Figure.add_subplot`.
+        map_projection : `~cartopy.crs.Projection` or `~mpl_toolkits.basemap.Basemap`
+            The cartopy or basemap projection instance. This is
+            passed automatically when calling axes-creation
+            commands like `~proplot.figure.Figure.add_subplot`.
         %(geo.format)s
 
         Other parameters

proplot/constructor.py

@@ -293,6 +293,13 @@
             + ', '.join(map(repr, PROJS_MISSING))
             + ' . Please consider updating cartopy.'
         )
+    PROJS_TABLE = (
+        'The known cartopy projection classes are:\n'
+        + '\n'.join(
+            ' ' + key + ' ' * (max(map(len, PROJS)) - len(key) + 10) + cls.__name__
+            for key, cls in PROJS.items()
+        )
+    )
 
 # Geographic feature properties
 FEATURES_CARTOPY = {  # positional arguments passed to NaturalEarthFeature
@@ -1393,6 +1400,7 @@ def Proj(name, basemap=None, **kwargs):
     basemap = _not_none(basemap, rc['basemap'])
     is_crs = Projection is not object and isinstance(name, Projection)
     is_basemap = Basemap is not object and isinstance(name, Basemap)
+    include_axes = kwargs.pop('include_axes', False)  # for error message
     if is_crs or is_basemap:
         proj = name
         package = 'cartopy' if is_crs else 'basemap'
@@ -1429,18 +1437,18 @@ def Proj(name, basemap=None, **kwargs):
         if 'latlim' in kwargs:
             kwargs['llcrnrlat'], kwargs['urcrnrlat'] = kwargs.pop('latlim')
         name = PROJ_ALIASES.get(name, name)
-        kwproj = PROJ_DEFAULTS.get(name, {}).copy()
-        kwproj.update(kwargs)
-        kwproj.setdefault('fix_aspect', True)
-        if kwproj.get('lon_0', 0) > 0:
-            kwproj['lon_0'] -= 360
+        proj_kw = PROJ_DEFAULTS.get(name, {}).copy()
+        proj_kw.update(kwargs)
+        proj_kw.setdefault('fix_aspect', True)
+        if proj_kw.get('lon_0', 0) > 0:
+            proj_kw['lon_0'] -= 360
         if name[:2] in ('np', 'sp'):
-            kwproj.setdefault('round', True)
+            proj_kw.setdefault('round', True)
         if name == 'geos':
-            kwproj.setdefault('rsphere', (6378137.00, 6356752.3142))
+            proj_kw.setdefault('rsphere', (6378137.00, 6356752.3142))
         reso = _not_none(
-            reso=kwproj.pop('reso', None),
-            resolution=kwproj.pop('resolution', None),
+            reso=proj_kw.pop('reso', None),
+            resolution=proj_kw.pop('resolution', None),
             default=rc['reso']
         )
         if reso in RESOS_BASEMAP:
@@ -1451,43 +1459,45 @@ def Proj(name, basemap=None, **kwargs):
                 + ', '.join(map(repr, RESOS_BASEMAP))
                 + '.'
             )
-        kwproj.update({'resolution': reso, 'projection': name})
+        proj_kw.update({'resolution': reso, 'projection': name})
         try:
-            proj = mbasemap.Basemap(**kwproj)  # will raise helpful warning
+            proj = mbasemap.Basemap(**proj_kw)  # will raise helpful warning
         except ValueError as err:
-            msg = str(err)
-            msg = msg.replace('projection', 'basemap projection')
-            raise ValueError(msg) from None
+            message = str(err)
+            message = message.strip()
+            message = message.replace('projection', 'basemap projection')
+            message = message.replace('supported', 'known')
+            if include_axes:
+                from . import axes as paxes  # avoid circular imports
+                message = message.replace('projection.', 'projection or axes subclass.')
+                message += '\nThe known axes subclasses are:\n' + paxes._cls_table
+            raise ValueError(message) from None
 
     # Cartopy
     # NOTE: Error message matches basemap invalid projection message
     else:
         import cartopy.crs as ccrs  # noqa: F401
         package = 'cartopy'
-        kwproj = {
-            PROJ_ALIASES_KW.get(key, key): value
-            for key, value in kwargs.items()
-        }
-        if name in PROJS:
+        proj_kw = {PROJ_ALIASES_KW.get(key, key): value for key, value in kwargs.items()}  # noqa: E501
+        if 'boundinglat' in proj_kw:
+            raise ValueError('"boundinglat" must be passed to the ax.format() command for cartopy axes.')  # noqa: E501
+        try:
             crs = PROJS[name]
-        else:
-            maxlen = max(map(len, PROJS))
-            raise ValueError(
-                f'{name!r} is an unknown cartopy projection class.\n'
-                'The known cartopy projection classes are:\n'
-                + '\n'.join(
-                    ' ' + key + ' ' * (maxlen - len(key) + 6) + crs.__name__
-                    for key, crs in PROJS.items()
-                )
+        except KeyError:
+            message = f'{name!r} is an unknown cartopy projection class.\n'
+            message += 'The known cartopy projection classes are:\n'
+            message += '\n'.join(
+                ' ' + key + ' ' * (max(map(len, PROJS)) - len(key) + 10) + cls.__name__
+                for key, cls in PROJS.items()
             )
+            if include_axes:
+                from . import axes as paxes  # avoid circular imports
+                message = message.replace('projection.', 'projection or axes subclass.')
+                message += '\nThe known axes subclasses are:\n' + paxes._cls_table
+            raise ValueError(message) from None
         if name == 'geos':  # fix common mistake
-            kwproj.pop('central_latitude', None)
-        if 'boundinglat' in kwproj:
-            raise ValueError(
-                '"boundinglat" must be passed to the ax.format() command '
-                'for cartopy axes.'
-            )
-        proj = crs(**kwproj)
+            proj_kw.pop('central_latitude', None)
+        proj = crs(**proj_kw)
 
     proj._proj_package = package
     return proj

proplot/figure.py

@@ -789,14 +789,15 @@ def _parse_proj(
             and constructor.Basemap is object
         ):
             raise ValueError(
-                f'Invalid projection name {proj!r}. Valid axes subclasses are '
-                + ', '.join(map(repr, paxes.CLASSES)) + '. If you are trying to '
-                + 'create a geographic axes then cartopy or basemap must be installed.'
+                f'Invalid projection name {proj!r}. If you are trying to create a '
+                'GeoAxes with a cartopy.crs.Projection or mpl_toolkits.basemap.Basemap '
+                'projection then cartopy or basemap must be installed. Otherwise the '
+                f'known axes subclasses are:\n{paxes._cls_table}'
             )
         # Search geographic projections
         # NOTE: Also raises errors due to unexpected projection type
         if name is None:
-            proj = constructor.Proj(proj, basemap=basemap, **proj_kw)
+            proj = constructor.Proj(proj, basemap=basemap, include_axes=True, **proj_kw)
             name = proj._proj_package
             kwargs['map_projection'] = proj