BigQuery: Hide error traceback in BigQuery cell magic (#8808)

* Hide error traceback in BigQuery cell magic

The traceback is an internal detail of the IPython magic, the users
should only see the relevant error information.

* Output BigQuery cell magic error message to stderr

Author: plamut

bigquery/google/cloud/bigquery/magics.py

@@ -130,6 +130,7 @@
 from __future__ import print_function
 
 import ast
+import sys
 import time
 from concurrent import futures
 
@@ -415,11 +416,20 @@ def _cell_magic(line, query):
     elif args.maximum_bytes_billed is not None:
         value = int(args.maximum_bytes_billed)
         job_config.maximum_bytes_billed = value
-    query_job = _run_query(client, query, job_config)
+
+    error = None
+    try:
+        query_job = _run_query(client, query, job_config)
+    except Exception as ex:
+        error = str(ex)
 
     if not args.verbose:
         display.clear_output()
 
+    if error:
+        print("\nERROR:\n", error, file=sys.stderr)
+        return
+
     result = query_job.to_dataframe(bqstorage_client=bqstorage_client)
     if args.destination_var:
         IPython.get_ipython().push({args.destination_var: result})

bigquery/tests/unit/test_magics.py

@@ -32,6 +32,7 @@
 except ImportError:  # pragma: NO COVER
     IPython = None
 
+from google.api_core import exceptions
 import google.auth.credentials
 
 try:
@@ -862,3 +863,30 @@ def test_bigquery_magic_with_improperly_formatted_params():
 
     with pytest.raises(SyntaxError):
         ip.run_cell_magic("bigquery", "--params {17}", sql)
+
+
+@pytest.mark.usefixtures("ipython_interactive")
+def test_bigquery_magic_omits_tracebacks_from_error_message():
+    ip = IPython.get_ipython()
+    ip.extension_manager.load_extension("google.cloud.bigquery")
+
+    credentials_mock = mock.create_autospec(
+        google.auth.credentials.Credentials, instance=True
+    )
+    default_patch = mock.patch(
+        "google.auth.default", return_value=(credentials_mock, "general-project")
+    )
+
+    run_query_patch = mock.patch(
+        "google.cloud.bigquery.magics._run_query",
+        autospec=True,
+        side_effect=exceptions.BadRequest("Syntax error in SQL query"),
+    )
+
+    with run_query_patch, default_patch, io.capture_output() as captured_io:
+        ip.run_cell_magic("bigquery", "", "SELECT foo FROM WHERE LIMIT bar")
+
+    output = captured_io.stderr
+    assert "400 Syntax error in SQL query" in output
+    assert "Traceback (most recent call last)" not in output
+    assert "Syntax error" not in captured_io.stdout