FIX: show bars when the first location is nan

Due to the way we handle units on the bar width having an invalid value in the
first position of the x bar (of y of barh) would effectively poison all of the
widths making all of the bars invisible.

This also renames the cbook function _safe_first_non_none function ->
_safe_first_finite and adjusts the behavior to also drop nans

closes matplotlib#23687

Author: tacaswell

lib/matplotlib/axes/_axes.py

@@ -2179,12 +2179,12 @@ def _convert_dx(dx, x0, xconv, convert):
             # removes the units from unit packages like `pint` that
             # wrap numpy arrays.
             try:
-                x0 = cbook._safe_first_non_none(x0)
+                x0 = cbook._safe_first_finite(x0)
             except (TypeError, IndexError, KeyError):
                 pass
 
             try:
-                x = cbook._safe_first_non_none(xconv)
+                x = cbook._safe_first_finite(xconv)
             except (TypeError, IndexError, KeyError):
                 x = xconv
 
@@ -2801,11 +2801,11 @@ def broken_barh(self, xranges, yrange, **kwargs):
         """
         # process the unit information
         if len(xranges):
-            xdata = cbook._safe_first_non_none(xranges)
+            xdata = cbook._safe_first_finite(xranges)
         else:
             xdata = None
         if len(yrange):
-            ydata = cbook._safe_first_non_none(yrange)
+            ydata = cbook._safe_first_finite(yrange)
         else:
             ydata = None
         self._process_unit_info(
@@ -3447,10 +3447,10 @@ def _upcast_err(err):
                     # safe_first_element because getitem is index-first not
                     # location first on pandas objects so err[0] almost always
                     # fails.
-                    isinstance(cbook._safe_first_non_none(err), np.ndarray)
+                    isinstance(cbook._safe_first_finite(err), np.ndarray)
             ):
                 # Get the type of the first element
-                atype = type(cbook._safe_first_non_none(err))
+                atype = type(cbook._safe_first_finite(err))
                 # Promote the outer container to match the inner container
                 if atype is np.ndarray:
                     # Converts using np.asarray, because data cannot
@@ -4313,7 +4313,7 @@ def _parse_scatter_color_args(c, edgecolors, kwargs, xsize,
         c_is_string_or_strings = (
             isinstance(c, str)
             or (np.iterable(c) and len(c) > 0
-                and isinstance(cbook._safe_first_non_none(c), str)))
+                and isinstance(cbook._safe_first_finite(c), str)))
 
         def invalid_shape_exception(csize, xsize):
             return ValueError(

lib/matplotlib/cbook/__init__.py

@@ -1703,10 +1703,10 @@ def safe_first_element(obj):
     This is an type-independent way of obtaining the first element,
     supporting both index access and the iterator protocol.
     """
-    return _safe_first_non_none(obj, skip_none=False)
+    return _safe_first_finite(obj, skip_nonfinite=False)
 
 
-def _safe_first_non_none(obj, skip_none=True):
+def _safe_first_finite(obj, *, skip_nonfinite=True):
     """
     Return the first non-None element in *obj*.
     This is a method for internal use.
@@ -1715,7 +1715,14 @@ def _safe_first_non_none(obj, skip_none=True):
     supporting both index access and the iterator protocol.
     The first non-None element will be obtained when skip_none is True.
     """
-    if skip_none is False:
+    def safe_isfinite(val):
+        try:
+            return np.isfinite(val) if np.isscalar(val) else True
+        except TypeError:
+            # This is something that numpy can not make heads or tails
+            # of, assume "finite"
+            return True
+    if skip_nonfinite is False:
         if isinstance(obj, collections.abc.Iterator):
             # needed to accept `array.flat` as input.
             # np.flatiter reports as an instance of collections.Iterator
@@ -1730,12 +1737,16 @@ def _safe_first_non_none(obj, skip_none=True):
                                "as input")
         return next(iter(obj))
     elif isinstance(obj, np.flatiter):
+        # TODO do the finite filtering on this
         return obj[0]
     elif isinstance(obj, collections.abc.Iterator):
         raise RuntimeError("matplotlib does not "
                            "support generators as input")
     else:
-        return next(val for val in obj if val is not None)
+        return next(
+            val for val in obj
+            if val is not None and safe_isfinite(val)
+        )
 
 
 def sanitize_sequence(data):

lib/matplotlib/dates.py

@@ -1908,7 +1908,7 @@ def default_units(x, axis):
             x = x.ravel()
 
         try:
-            x = cbook._safe_first_non_none(x)
+            x = cbook._safe_first_finite(x)
         except (TypeError, StopIteration):
             pass
 

lib/matplotlib/tests/test_axes.py

@@ -8109,3 +8109,27 @@ def test_get_xticklabel():
     for ind in range(10):
         assert ax.get_xticklabels()[ind].get_text() == f'{ind}'
         assert ax.get_yticklabels()[ind].get_text() == f'{ind}'
+
+
+def test_bar_leading_nan():
+
+    barx = np.arange(3, dtype=float)
+    barheights = np.array([0.5, 1.5, 2.0])
+    barstarts = np.array([0.77]*3)
+
+    barx[0] = np.NaN
+
+    fig, ax = plt.subplots()
+
+    bars = ax.bar(barx, barheights, bottom=barstarts)
+
+    hbars = ax.barh(barx, barheights, left=barstarts)
+
+    for bar_set in (bars, hbars):
+        # the first bar should have a nan in the location
+        nanful, *rest = bar_set
+        assert (~np.isfinite(nanful.xy)).any()
+        assert np.isfinite(nanful.get_width())
+        for b in rest:
+            assert np.isfinite(b.xy).all()
+            assert np.isfinite(b.get_width())

lib/matplotlib/tests/test_cbook.py

@@ -602,7 +602,7 @@ def test_flatiter():
     it = x.flat
     assert 0 == next(it)
     assert 1 == next(it)
-    ret = cbook._safe_first_non_none(it)
+    ret = cbook._safe_first_finite(it)
     assert ret == 0
 
     assert 0 == next(it)
@@ -758,7 +758,7 @@ def test_contiguous_regions():
 def test_safe_first_element_pandas_series(pd):
     # deliberately create a pandas series with index not starting from 0
     s = pd.Series(range(5), index=range(10, 15))
-    actual = cbook._safe_first_non_none(s)
+    actual = cbook._safe_first_finite(s)
     assert actual == 0
 
 
@@ -893,5 +893,5 @@ def test_format_approx():
 def test_safe_first_element_with_none():
     datetime_lst = [date.today() + timedelta(days=i) for i in range(10)]
     datetime_lst[0] = None
-    actual = cbook._safe_first_non_none(datetime_lst)
+    actual = cbook._safe_first_finite(datetime_lst)
     assert actual is not None and actual == datetime_lst[1]

lib/matplotlib/units.py

@@ -197,7 +197,7 @@ def get_converter(self, x):
             except KeyError:
                 pass
         try:  # If cache lookup fails, look up based on first element...
-            first = cbook._safe_first_non_none(x)
+            first = cbook._safe_first_finite(x)
         except (TypeError, StopIteration):
             pass
         else: