(core) Add ChoiceList type, cell widget, and editor widget.

Summary:
- Adds a new ChoiceList type, and widgets to view and edit it.
- Store in SQLite as a JSON string
- Support conversions between ChoiceList and other types

Test Plan: Added browser tests, and a test for how these values are stored

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2803

sandbox/grist/column.py

@@ -1,3 +1,4 @@
+import json
 import types
 from collections import namedtuple
 
@@ -294,6 +295,26 @@ class PositionColumn(NumericColumn):
     return new_values, [(self._sorted_rows[i], pos) for (i, pos) in adjustments]
 
 
+class ChoiceListColumn(BaseColumn):
+  """
+  ChoiceListColumn's default value is None, but is presented to formulas as the empty list.
+  """
+  def set(self, row_id, value):
+    # When a JSON string is loaded, set it to a tuple parsed from it. When a list is loaded,
+    # convert to a tuple to keep values immutable.
+    if isinstance(value, basestring) and value.startswith('['):
+      try:
+        value = tuple(json.loads(value))
+      except Exception:
+        pass
+    elif isinstance(value, list):
+      value = tuple(value)
+    super(ChoiceListColumn, self).set(row_id, value)
+
+  def _make_rich_value(self, typed_value):
+    return () if typed_value is None else typed_value
+
+
 class BaseReferenceColumn(BaseColumn):
   """
   Base class for ReferenceColumn and ReferenceListColumn.
@@ -386,6 +407,7 @@ class ReferenceListColumn(BaseReferenceColumn):
 usertypes.BaseColumnType.ColType = DataColumn
 usertypes.Reference.ColType = ReferenceColumn
 usertypes.ReferenceList.ColType = ReferenceListColumn
+usertypes.ChoiceList.ColType = ChoiceListColumn
 usertypes.DateTime.ColType = DateTimeColumn
 usertypes.Date.ColType = DateColumn
 usertypes.PositionNumber.ColType = PositionColumn

sandbox/grist/grist.py

@@ -6,7 +6,7 @@ a consistent API accessible with only "import grist".
 
 # These imports are used in processing generated usercode.
 from usertypes import Any, Text, Blob, Int, Bool, Date, DateTime, \
-Numeric, Choice, Id, Attachments, AltText, ifError
+  Numeric, Choice, ChoiceList, Id, Attachments, AltText, ifError
 from usertypes import PositionNumber, ManualSortPos, Reference, ReferenceList, formulaType
 from table import UserTable
 from records import Record, RecordSet

sandbox/grist/usertypes.py

@@ -11,7 +11,10 @@ Python's array.array. However, at least on the Python side, it means that we nee
 data structure for values of the wrong type, and the memory savings aren't that great to be worth
 the extra complexity.
 """
+import csv
+import cStringIO
 import datetime
+import json
 import six
 import objtypes
 from objtypes import AltText
@@ -29,6 +32,7 @@ _type_defaults = {
   'Blob':         None,
   'Bool':         False,
   'Choice':       '',
+  'ChoiceList':   None,
   'Date':         None,
   'DateTime':     None,
   'Id':           0,
@@ -319,6 +323,53 @@ class Choice(Text):
   pass
 
 
+class ChoiceList(BaseColumnType):
+  """
+  ChoiceList is the type for a field holding a list of strings from a set of acceptable choices.
+  """
+  def do_convert(self, value):
+    if not value:
+      return None
+    elif isinstance(value, basestring):
+      # If it's a string that looks like JSON, try to parse it as such.
+      if value.startswith('['):
+        try:
+          return tuple(str(item) for item in json.loads(value))
+        except Exception:
+          pass
+      return value
+    else:
+      # Accepts other kinds of iterables; if that doesn't work, fail the conversion too.
+      return tuple(str(item) for item in value)
+
+  @classmethod
+  def is_right_type(cls, value):
+    return value is None or (isinstance(value, (tuple, list)) and
+                             all(isinstance(item, basestring) for item in value))
+
+  @classmethod
+  def typeConvert(cls, value):
+    if isinstance(value, basestring) and not value.startswith('['):
+      # Try to parse as CSV. If this doesn't work, we'll still try usual conversions later.
+      try:
+        tags = next(csv.reader([value]))
+        return tuple(t.strip() for t in tags if t.strip())
+      except Exception:
+        pass
+    return value
+
+  @classmethod
+  def toString(cls, value):
+    if isinstance(value, (tuple, list)):
+      try:
+        buf = cStringIO.StringIO()
+        csv.writer(buf).writerow(value)
+        return buf.getvalue().strip()
+      except Exception:
+        pass
+    return value
+
+
 class PositionNumber(BaseColumnType):
   """
   PositionNumber is the type for a position field used to order records in record lists.