Add support for multi-flags to flag_dict_to_args helper.

Multi-flags are identified by an optional second argument consisting of a set of multi-flag names.

PiperOrigin-RevId: 305287708
Change-Id: I26f1f1f40771d7e3a2d651812e6b3bf6fe3c5c17

2 files changed, 22 insertions, 3 deletions

diff --git a/absl/flags/_helpers.py b/absl/flags/_helpers.py
index 817daa9..68b8cfc 100644
--- a/absl/flags/_helpers.py
+++ b/absl/flags/_helpers.py
@@ -318,7 +318,7 @@ def text_wrap(text, length=None, indent='', firstline_indent=None):
   return '\n'.join(result)
 
 
-def flag_dict_to_args(flag_map):
+def flag_dict_to_args(flag_map, multi_flags=None):
   """Convert a dict of values into process call parameters.
 
   This method is used to convert a dictionary into a sequence of parameters
@@ -331,8 +331,12 @@ def flag_dict_to_args(flag_map):
         * If value is True, then only the name is emitted.
         * If value is False, then only the name prepended with 'no' is emitted.
         * If value is a string then --name=value is emitted.
-        * If value is a collection, this will emit --name=value1,value2,value3.
+        * If value is a collection, this will emit --name=value1,value2,value3,
+          unless the flag name is in multi_flags, in which case this will emit
+          --name=value1 --name=value2 --name=value3.
         * Everything else is converted to string an passed as such.
+    multi_flags: set, names (strings) of flags that should be treated as
+        multi-flags.
   Yields:
     sequence of string suitable for a subprocess execution.
   """
@@ -350,7 +354,11 @@ def flag_dict_to_args(flag_map):
     else:
       # Now we attempt to deal with collections.
       try:
-        yield '--%s=%s' % (key, ','.join(str(item) for item in value))
+        if multi_flags and key in multi_flags:
+          for item in value:
+            yield '--%s=%s' % (key, str(item))
+        else:
+          yield '--%s=%s' % (key, ','.join(str(item) for item in value))
       except TypeError:
         # Default case.
         yield '--%s=%s' % (key, value)
diff --git a/absl/flags/tests/flags_test.py b/absl/flags/tests/flags_test.py
index 7bb7dca..0a54cd3 100644
--- a/absl/flags/tests/flags_test.py
+++ b/absl/flags/tests/flags_test.py
@@ -67,6 +67,17 @@ class FlagDictToArgsTest(absltest.TestCase):
             '--loadthatstuff=42,hello,goodbye'),
         flags.flag_dict_to_args(arg_dict))
 
+  def test_flatten_google_flag_map_with_multi_flag(self):
+    arg_dict = {
+        'some_list': ['value1', 'value2'],
+        'some_multi_string': ['value3', 'value4'],
+    }
+    self.assertSameElements(
+        (
+            '--some_list=value1,value2', '--some_multi_string=value3',
+            '--some_multi_string=value4'),
+        flags.flag_dict_to_args(arg_dict, multi_flags={'some_multi_string'}))
+
 
 class Fruit(enum.Enum):
   apple = 1