[FIX] OWRank: Select Attributes fixes and improvements

[thocevar]

• allow change of selection method from All to Manual
• add selection method and selected_rows to context settings

Includes

• Code changes
• Tests
• Documentation

[thocevar]

Loading the manually selected rows from context settings doesn't work. Method autoSelection doesn't seem to successfully select the rows in the view's selection model. As a consequence, on_select overwrites the selected_rows with an empty list.

[codecov-io]

Codecov Report

Merging #3084 into master will increase coverage by 0.01%.
The diff coverage is 60%.

@@            Coverage Diff             @@
##           master    #3084      +/-   ##
==========================================
+ Coverage   82.42%   82.43%   +0.01%     
==========================================
  Files         335      335              
  Lines       58037    58105      +68     
==========================================
+ Hits        47838    47901      +63     
- Misses      10199    10204       +5

[ales-erjavec]

Loading the manually selected rows from context settings doesn't work.

Try

diff --git a/Orange/widgets/data/owrank.py b/Orange/widgets/data/owrank.py
index 83436d3ae..c0a009ff8 100644
--- a/Orange/widgets/data/owrank.py
+++ b/Orange/widgets/data/owrank.py
@@ -339,7 +339,7 @@ class OWRank(OWWidget):
             self.selectionMethod = OWRank.SelectNBest
 
         self.openContext(data)
-        self.setSelectionMethod(self.selectionMethod)
+        self.selectButtons.button(self.selectionMethod).setChecked(True)
 
     def handleNewSignals(self):
         self.setStatusMessage('Running')

setSelectionMethod calls autoSelection, but in set_data the ranksModel is still empty.

[lanzagar]

You can delete the row above as well and use the long version below (it is now only used once)

[lanzagar]

While fixing this, could you also change it so that commit is only called once.