[ASIM-6921] Keep the details of errors raised by evaluated JS code

src/qmxgraph/_web_view.py

@@ -1,4 +1,5 @@
 # Dynamic dependency that may mess freezing tools if not included
+import json
 from enum import auto
 from enum import Enum
 from typing import Any
@@ -132,7 +133,8 @@ def eval_js(self, script, *, timeout_ms: int = 10_000) -> Any:
         """
         self._check_valid_eval_state()
         with wait_callback_called(timeout_ms=timeout_ms) as callback:
-            self.page().runJavaScript(script, callback)
+            self.page().runJavaScript(_in_page_context(script), callback)
+        # Leaving the block guarantees the callback was called, as it raises on timeout.
         assert callback.args is not None
         return callback.args[0]
 
@@ -150,7 +152,7 @@ def eval_js_async(self, script: str) -> None:
         :param script: A JavaScript statement.
         """
         self._check_valid_eval_state()
-        self.page().runJavaScript(script)
+        self.page().runJavaScript(_in_page_context(script))
 
     def _check_valid_eval_state(self) -> None:
         """Check the view is in a valid state to evaluate JS commands."""
@@ -167,3 +169,11 @@ def dragMoveEvent(self, event):
 
     def dropEvent(self, event):
         self.on_drop_event.emit(event)
+
+
+def _in_page_context(script: str) -> str:
+    """
+    Wrap a script so the page evaluates it as its own code (see `qmxgraphEval`), otherwise
+    its uncaught errors reach the error bridge without any details.
+    """
+    return f"qmxgraphEval({json.dumps(script)})"

src/qmxgraph/page/error_redirect.js

@@ -29,3 +29,19 @@ window.onerror = function (msg, url, lineNo, columnNo, error) {
 
     bridge_error_handler.error_slot(msg, url, lineNo, columnNo);
 };
+
+/**
+ * Evaluates a script on behalf of Python, returning the value of its last statement.
+ *
+ * Chromium reports uncaught errors from scripts injected by `runJavaScript` as a bare
+ * "Script error." with no details. Evaluated from here, the code counts as the page's own,
+ * so `onerror` above receives its message and stack.
+ *
+ * @param {string} source The script to evaluate, in global scope.
+ * @returns {*} The value of the script's last statement.
+ */
+window.qmxgraphEval = function (source) {
+    "use strict";
+    /* jshint evil: true */
+    return (0, eval)(source);
+};

tests/test_qt_js_integration.py

@@ -29,15 +29,12 @@
 from qmxgraph.widget import QmxGraph
 
 
-# TODO(ASIM-6921): Remove once JS errors are no longer muted.
-@pytest.mark.xfail(
-    reason="QtWebEngine 5.15.15 reports JS errors as a bare 'Script error.'", strict=True
-)
-def test_error_redirection(loaded_graph) -> None:
+def test_error_redirection(loaded_graph: QmxGraph) -> None:
     """
     It is possible to redirect errors in JS code to Python/Qt side.
 
-    :type loaded_graph: qmxgraph.widget.qmxgraph
+    The stack is only checked up to the error's position in the evaluated code, as the frames
+    after it belong to the evaluation machinery.
     """
     error_redirection = loaded_graph.error_bridge
 
@@ -46,15 +43,40 @@ def test_error_redirection(loaded_graph) -> None:
 
     assert cb.args is not None
     msg, url, line, column = cb.args
-    expected = textwrap.dedent(
+    expected_start = textwrap.dedent(
         """\
         Uncaught Error: test
         stack:
         Error: test
-            at <anonymous>:1:7"""
+        """
     )
     assert (url, line, column) == ("qrc:/", 1, 1)
-    assert msg == expected
+    assert msg.startswith(expected_start)
+    assert "<anonymous>:1:7" in msg
+
+
+@pytest.mark.parametrize(
+    "statement, expected_error",
+    [
+        ("api.noSuchFunction(1)", "TypeError: api.noSuchFunction is not a function"),
+        ("api.updateTable(", "SyntaxError: Unexpected end of input"),
+    ],
+)
+def test_error_redirection_from_evaluated_code(
+    loaded_graph: QmxGraph, statement: str, expected_error: str
+) -> None:
+    """
+    Regression test for ASIM-6921: errors raised by the evaluated code itself, like calling a
+    function that doesn't exist or a syntax error, reached Python as a bare "Script error.",
+    as Chromium hides the details of errors from scripts injected by `runJavaScript`.
+    """
+    with wait_signals_called(loaded_graph.error_bridge.on_error) as cb:
+        eval_js(loaded_graph, statement)
+
+    assert cb.args is not None
+    msg, url, line, column = cb.args
+    assert msg.startswith(f"Uncaught {expected_error}\nstack:\n")
+    assert (url, line) == ("qrc:/", 1)
 
 
 def test_events_bridge_delayed_signals(graph, qtbot, mocker) -> None: