Deprecate old paths for module-availability testers

qiskit/visualization/__init__.py

@@ -114,6 +114,7 @@
 
 import os
 import sys
+import warnings
 
 from qiskit.visualization.counts_visualization import plot_histogram
 from qiskit.visualization.state_visualization import (
@@ -127,9 +128,6 @@
 from qiskit.visualization.transition_visualization import visualize_transition
 from qiskit.visualization.array import array_to_latex
 
-# NOTE (Jake Lishman, 2022-01-12): for backwards compatibility. Deprecate these paths in Terra 0.21.
-from qiskit.utils.optionals import HAS_MATPLOTLIB, HAS_PYLATEX, HAS_PIL, HAS_PDFTOCAIRO
-
 from .circuit_visualization import circuit_drawer
 from .dag_visualization import dag_drawer
 from .exceptions import VisualizationError
@@ -140,3 +138,24 @@
 from .pulse_visualization import pulse_drawer
 from .pulse_v2 import draw as pulse_drawer_v2
 from .timeline import draw as timeline_drawer
+
+_DEPRECATED_NAMES = {
+    "HAS_MATPLOTLIB",
+    "HAS_PYLATEX",
+    "HAS_PIL",
+    "HAS_PDFTOCAIRO",
+}
+
+
+def __getattr__(name):
+    if name in _DEPRECATED_NAMES:
+        from qiskit.utils import optionals
+
+        warnings.warn(
+            f"Accessing '{name}' from '{__name__}' is deprecated since Qiskit Terra 0.21 "
+            "and will be removed in a future release. Use 'qiskit.utils.optionals' instead.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return getattr(optionals, name)
+    raise AttributeError(f"module '{__name__}' has no attribute '{name}'")

releasenotes/notes/deprecate-old-optional-paths-982466a6336e4794.yaml

@@ -0,0 +1,9 @@
+---
+deprecations:
+  - |
+    Accessing several old toggles (``HAS_MATPLOTLIB``, ``HAS_PDFTOCAIRO``,
+    ``HAS_PYLATEX`` and ``HAS_PIL``) from the :mod:`qiskit.visualization` module
+    is now deprecated, and these import paths will be removed in a future
+    version of Qiskit Terra.  The same objects should instead be accessed
+    through :mod:`qiskit.utils.optionals`, which contains testers for almost all
+    of Terra's optional dependencies.