Backport PR matplotlib#31819: FIX: use data values in bar_label

Author: timhoffm

lib/matplotlib/axes/_axes.py

@@ -2907,10 +2907,8 @@ def sign(x):
 
             if orientation == "vertical":
                 extrema = max(y0, y1) if dat >= 0 else min(y0, y1)
-                length = abs(y0 - y1)
             else:  # horizontal
                 extrema = max(x0, x1) if dat >= 0 else min(x0, x1)
-                length = abs(x0 - x1)
 
             if err is None or np.size(err) == 0:
                 endpt = extrema
@@ -2919,11 +2917,6 @@ def sign(x):
             else:  # horizontal
                 endpt = err[:, 0].max() if dat >= 0 else err[:, 0].min()
 
-            if label_type == "center":
-                value = sign(dat) * length
-            else:  # edge
-                value = extrema
-
             if label_type == "center":
                 xy = (0.5, 0.5)
                 kwargs["xycoords"] = (
@@ -2966,9 +2959,9 @@ def sign(x):
 
             if lbl is None:
                 if isinstance(fmt, str):
-                    lbl = cbook._auto_format_str(fmt, value)
+                    lbl = cbook._auto_format_str(fmt, dat)
                 elif callable(fmt):
-                    lbl = fmt(value)
+                    lbl = fmt(dat)
                 else:
                     raise TypeError("fmt must be a str or callable")
             annotation = self.annotate(lbl,

lib/matplotlib/tests/test_axes.py

@@ -13,7 +13,7 @@
 from types import SimpleNamespace
 import unittest.mock
 
-import dateutil.tz
+import dateutil
 
 import numpy as np
 from numpy import ma
@@ -9459,6 +9459,13 @@ def test_nan_barlabels():
     assert np.allclose(ax.get_ylim(), (0.0, 3.0))
 
 
+def test_int_fmt_bar_label():
+    fig, ax = plt.subplots()
+    bars = ax.bar(['foo', 'bar'], [5, 7])
+    labels = ax.bar_label(bars, fmt='{:d}')
+    assert [l.get_text() for l in labels] == ['5', '7']
+
+
 def test_patch_bounds():  # PR 19078
     fig, ax = plt.subplots()
     ax.add_patch(mpatches.Wedge((0, -1), 1.05, 60, 120, width=0.1))