# HG changeset patch
# User Aurélien Campéas <aurelien.campeas@pythonian.fr>
# Date 1724318343 -7200
#      Thu Aug 22 11:19:03 2024 +0200
# Node ID 17f960c26c57c5d49c3d43f6dbd6252d085dad74
# Parent  928ee34c09fba6c06f7ee6213454cf420ab07416
api/update: fix the documentation

diff --git a/test/test_tsio.py b/test/test_tsio.py
--- a/test/test_tsio.py
+++ b/test/test_tsio.py
@@ -1103,6 +1103,14 @@
     )
 
 
+def test_empty_update(engine, tsh):
+    ts = genserie(datetime(2010, 1, 1), 'D', 11)
+    d1 = tsh.update(engine, ts, 'empty-update', 'Babar')
+    assert len(d1)
+    d2 = tsh.update(engine, ts, 'empty-update', 'Babar')
+    assert not len(d2)
+
+
 def test_point_deletion(engine, tsh):
     ts_begin = genserie(datetime(2010, 1, 1), 'D', 11)
     ts_begin.iloc[-1] = np.nan
diff --git a/tshistory/api.py b/tshistory/api.py
--- a/tshistory/api.py
+++ b/tshistory/api.py
@@ -119,10 +119,12 @@
         the new version.
 
         A series made of the changed points is returned.  If there was
-        no change, None is returned and no new version is created.
+        no change, an empty series is returned and no new version is
+        created.
 
-        New points are added, changed points are changed,
-        points with NaN are _erased_.
+        New points are added, changed points are changed, points with
+        NaN are dropped if `keepnans` is False (by default) or
+        _erased_ if True.
 
         The `author` is mandatory.
         The `metadata` dictionary allows to associate any metadata
@@ -131,10 +133,6 @@
         It is possible to force an `insertion_date`, which can only be
         higher than the previous `insertion_date`.
 
-        The `keepnans` flag will treat, if true, the Nans values as
-        erasures. If false, we do a dropna() call on the series before
-        the actual update.
-
         .. highlight:: python
         .. code-block:: python