Robustify preview module (#2398)

* make preview module more robust

catch import errors so an existing arviz-xyz
broken installation doesn't affect regular arviz

* add info element and logging

* docs and linters

* use markdown file for docs

arviz/preview.py

@@ -1,17 +1,48 @@
-# pylint: disable=unused-import,unused-wildcard-import,wildcard-import
+# pylint: disable=unused-import,unused-wildcard-import,wildcard-import,invalid-name
 """Expose features from arviz-xyz refactored packages inside ``arviz.preview`` namespace."""
+import logging
+
+_log = logging.getLogger(__name__)
+
+info = ""
 
 try:
     from arviz_base import *
+
+    status = "arviz_base available, exposing its functions as part of arviz.preview"
+    _log.info(status)
 except ModuleNotFoundError:
-    pass
+    status = "arviz_base not installed"
+    _log.info(status)
+except ImportError:
+    status = "Unable to import arviz_base"
+    _log.info(status, exc_info=True)
+
+info += status + "\n"
 
 try:
-    import arviz_stats
+    from arviz_stats import *
+
+    status = "arviz_stats available, exposing its functions as part of arviz.preview"
+    _log.info(status)
 except ModuleNotFoundError:
-    pass
+    status = "arviz_stats not installed"
+    _log.info(status)
+except ImportError:
+    status = "Unable to import arviz_stats"
+    _log.info(status, exc_info=True)
+info += status + "\n"
 
 try:
     from arviz_plots import *
+
+    status = "arviz_plots available, exposing its functions as part of arviz.preview"
+    _log.info(status)
 except ModuleNotFoundError:
-    pass
+    status = "arviz_plots not installed"
+    _log.info(status)
+except ImportError:
+    status = "Unable to import arviz_plots"
+    _log.info(status, exc_info=True)
+
+info += status + "\n"

doc/source/api/index.rst

@@ -18,5 +18,6 @@ API Reference
     plot_utils
     utils
     rcparams
+    preview
     wrappers
     stats_refitting

doc/source/api/preview.md

@@ -0,0 +1,11 @@
+(preview_api)=
+
+# Preview
+This module give access to upcoming refactored features by exposing
+all objects in [arviz-base](https://arviz-base.readthedocs.io/en/latest/),
+[arviz-stats](https://arviz-stats.readthedocs.io/en/latest/) and
+[arviz-plots](https://arviz-plots.readthedocs.io/en/latest/)
+under a single namespace: `arviz.preview`.
+
+In addition, there is also an `arviz.preview.info` to check availability
+of the different sub-libraries.

doc/source/getting_started/Installation.rst

@@ -26,6 +26,9 @@ Use the below pip command to install ArviZ with all of its :ref:`Optional-depend
 
     pip install "arviz[all]"
 
+It is also possible to use ``pip install "arviz[preview]"` to access
+:ref:`upcoming refactored features <preview_api>`.
+
 Using conda-forge
 =================