Add support for tuple to collection subjects

`tuple`s are as list-like or more than `depset`s, but previously
resulted in a `fail` when passed to collection subject functions.

Along the way remove an incorrect comment about `str` being iterable,
which it is in Python but not in Starlark.

Author: fmeum

lib/private/truth_common.bzl

@@ -126,11 +126,12 @@ def to_list(obj):
     """Attempt to convert the object to a list, else error.
 
     NOTE: This only supports objects that are typically understood as
-    lists, not any iterable. Types like `dict` and `str` are iterable,
-    but will be rejected.
+    lists, not any iterable. Types like `dict` are iterable, but will
+    be rejected.
 
     Args:
-        obj: ([`list`] | [`depset`]) The object to convert to a list.
+        obj: ([`list`] | [`depset`] | [`tuple`]) The object to convert to a
+            list.
 
     Returns:
         [`list`] of the object
@@ -141,5 +142,7 @@ def to_list(obj):
         return obj
     elif types.is_depset(obj):
         return obj.to_list()
+    elif types.is_tuple(obj):
+        return list(obj)
     else:
         fail("Unable to convert to list: {}".format(repr_with_type(obj)))

tests/truth_tests.bzl

@@ -538,6 +538,34 @@ def _collection_contains_exactly_test(env, _target):
         msg = "check same elements out of order",
     )
 
+    subject = truth.expect(fake_env).that_collection(("one", "four", "three", "two", "five"))
+    order = subject.contains_exactly(("one", "two", "three", "four", "five"))
+    _assert_no_failures(
+        fake_env,
+        env = env,
+        msg = "check same elements with expected in different order",
+    )
+    order.in_order()
+    _assert_failure(
+        fake_env,
+        [
+            "expected values all found, but with incorrect order:",
+            "0: one found at offset 0",
+            "1: two found at offset 3",
+            "2: three found at offset 2",
+            "3: four found at offset 1",
+            "4: five found at offset 4",
+            "actual values:",
+            "0: one",
+            "1: four",
+            "2: three",
+            "3: two",
+            "4: five",
+        ],
+        env = env,
+        msg = "check same elements out of order",
+    )
+
     _end(env, fake_env)
 
 _suite.append(collection_contains_exactly_test)