ModelTester for recursive tree models

[phil65]

I´m running into a recursive loop when using the ModelTester with recursive tree models.
QAbstractItemModelTester gained an option to not call fetchMore with Qt6.4. ( https://doc.qt.io/qt-6/qabstractitemmodeltester.html#setUseFetchMore )
Since the _qt_tester attribute of ModelTester is only set after calling ModelTester.check(), there is no way to use that option.
Would be nice if that option could get added.
Thank you!

[The-Compiler]

Makes sense to support that option (and backport the logic to our Python reimplementation), yep!

Relevant change: Use QAbstractItemModelTester or QFileSystemModel (Ie5d2e22f) · Gerrit Code Review

No other relevant changes in Qt so far:

df9d882d41 Port from container.count()/length() to size()
76b07b05f0 Doc: add missing "see also"
2f35653a30 Use QAbstractItemModelTester or QFileSystemModel
05fc3aef53 Use SPDX license identifiers
b6759ff81c QAbstractItemModelTester: Fix typos in debug output    # <- Python reimplementation is here

[The-Compiler]

I did some initial work on this:

diff --git i/src/pytestqt/modeltest.py w/src/pytestqt/modeltest.py
index b2df3fe..c3d0340 100644
--- i/src/pytestqt/modeltest.py
+++ w/src/pytestqt/modeltest.py
@@ -71,6 +71,7 @@ class ModelTester:
     def __init__(self, config):
         self._model = None
         self._fetching_more = None
+        self._use_fetch_more = True
         self._insert = None
         self._remove = None
         self._changing = []
@@ -95,7 +96,7 @@ def _modelindex_debug(self, index):
                 id(index),
             )
 
-    def check(self, model, force_py=False):
+    def check(self, model, force_py=False, use_fetch_more=True):
         """Runs a series of checks in the given model.
 
         Connect to all of the models signals.
@@ -106,6 +107,9 @@ def check(self, model, force_py=False):
         :param force_py:
           Force using the Python implementation, even if the C++ implementation
           is available.
+        :param use_fetch_more:
+          Set to ``False`` to disable using ``fetchMore()`` on the model. If
+          using the Qt implementation, this needs Qt 6.4 or newer.
         """
         assert model is not None
 
@@ -116,6 +120,10 @@ def check(self, model, force_py=False):
             self._qt_tester = qt_api.QtTest.QAbstractItemModelTester(
                 model, reporting_mode
             )
+            if not use_fetch_more:
+                # If using use_fetch_more=False with Qt < 6.4, this will raise
+                # an AttributeError, which we let propagate.
+                self._qt_tester.setUseFetchMore(False)
             self._debug("Using Qt C++ tester")
             return
 
@@ -123,6 +131,7 @@ def check(self, model, force_py=False):
 
         self._model = model
         self._fetching_more = False
+        self._use_fetch_more = use_fetch_more
         self._insert = []
         self._remove = []
         self._changing = []
@@ -943,6 +952,8 @@ def _has_children(self, parent=qt_api.QtCore.QModelIndex()):
 
     def _fetch_more(self, parent):
         """Call ``fetchMore`` on the model and set ``self._fetching_more``."""
+        if not self._use_fetch_more:
+            return
         self._fetching_more = True
         self._model.fetchMore(parent)
         self._fetching_more = False
diff --git i/tests/test_modeltest.py w/tests/test_modeltest.py
index 665f125..c32f8de 100644
--- i/tests/test_modeltest.py
+++ w/tests/test_modeltest.py
@@ -302,21 +302,41 @@ def rowCount(self, parent=None):
     assert model.row_count_did_run
 
 
-def test_fetch_more(qtmodeltester):
-    class Model(qt_api.QtGui.QStandardItemModel):
-        def canFetchMore(self, parent):
-            return True
+class FetchMoreModel(qt_api.QtGui.QStandardItemModel):
 
-        def fetchMore(self, parent):
-            """Force a re-check while fetching more."""
-            self.setData(self.index(0, 0), "bar")
+    def __init__(self, fetch_more_allowed=True, parent=None):
+        super().__init__(parent)
+        self._fetch_more_allowed = fetch_more_allowed
 
-    model = Model()
+    def canFetchMore(self, parent):
+        return True
+
+    def fetchMore(self, parent):
+        """Force a re-check while fetching more."""
+        assert self._fetch_more_allowed
+        self.setData(self.index(0, 0), "bar")
+
+
+def test_fetch_more(qtmodeltester):
+    model = FetchMoreModel()
     item = qt_api.QtGui.QStandardItem("foo")
     model.setItem(0, 0, item)
     qtmodeltester.check(model, force_py=True)
 
 
+@pytest.mark.parametrize("force_py", [True, False])
+def test_fetch_more_disabled(qtmodeltester, force_py):
+    model = FetchMoreModel(fetch_more_allowed=False)
+    item = qt_api.QtGui.QStandardItem("foo")
+    model.setItem(0, 0, item)
+    try:
+        # Will raise in the model if fetchMore is called
+        qtmodeltester.check(model, force_py=force_py, use_fetch_more=False)
+    except AttributeError as e:
+        # Qt tester on Qt < 6.4
+        pytest.skip(str(e))
+
+
 def test_invalid_parent(qtmodeltester):
     class Model(qt_api.QtGui.QStandardItemModel):
         def parent(self, index):

but the tests fail:

====================================================== FAILURES ======================================================
__________________________________________ test_fetch_more_disabled[False] ___________________________________________
CALL ERROR: Exceptions caught in Qt event loop:
________________________________________________________________________________
Traceback (most recent call last):
  File "/home/florian/proj/pytest-qt/tests/test_modeltest.py", line 316, in fetchMore
    assert self._fetch_more_allowed
AssertionError: assert False
 +  where False = <test_modeltest.FetchMoreModel object at 0x7f867950e7a0>._fetch_more_allowed
________________________________________________________________________________
Traceback (most recent call last):
  File "/home/florian/proj/pytest-qt/tests/test_modeltest.py", line 316, in fetchMore
    assert self._fetch_more_allowed
AssertionError: assert False
 +  where False = <test_modeltest.FetchMoreModel object at 0x7f867950e7a0>._fetch_more_allowed
________________________________________________________________________________
------------------------------------------------ Captured stdout call ------------------------------------------------
modeltest: Using Qt C++ tester

and I believe this is Qt's fault:

• Given that useFetchMore is only a property, it follows that it needs to be set after creating the model tester and passing a model to it
• However, passing a model to it immediately runs all tests, which calls nonDestructiveBasicTest
• That in turn already calls fetchMore(), before we even had a chance to disable that

Not sure if I should report this as a Qt bug, or just adjust the test so it allows fetchMore to be called exactly once...

[phil65]

Did you try setting the property in the constructor?
QAbstractItemModelTester(model, useFetchMore=False)

(With Qt for Python, all properties can be set via constructor)

[The-Compiler]

That's just syntactic sugar for:

tester = QAbstractItemModelTester(model)
tester.setUseFetchMore(False)

so it shows the same problem as well.

[phil65]

Okay. Thanks for trying!