From 795502e07d66b5516c24ed1668c6e3afd1f73091 Mon Sep 17 00:00:00 2001
From: Peter Lamut <inbox@peterlamut.com>
Date: Mon, 29 Jul 2019 18:12:01 +0200
Subject: [PATCH 1/2] 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.
---
 bigquery/google/cloud/bigquery/magics.py | 11 +++++++++-
 bigquery/tests/unit/test_magics.py       | 27 ++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/bigquery/google/cloud/bigquery/magics.py b/bigquery/google/cloud/bigquery/magics.py
index 9bf2019c5c2e..dc2c0f59278a 100644
--- a/bigquery/google/cloud/bigquery/magics.py
+++ b/bigquery/google/cloud/bigquery/magics.py
@@ -417,11 +417,20 @@ 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)
+        return
+
     result = query_job.to_dataframe(bqstorage_client=bqstorage_client)
     if args.destination_var:
         IPython.get_ipython().push({args.destination_var: result})
diff --git a/bigquery/tests/unit/test_magics.py b/bigquery/tests/unit/test_magics.py
index 44e0571d1ee4..93eeb78f2d4c 100644
--- a/bigquery/tests/unit/test_magics.py
+++ b/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:
@@ -815,3 +816,29 @@ 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.stdout
+    assert "400 Syntax error in SQL query" in output
+    assert "Traceback (most recent call last)" not in output

From 71237531518abc72a55bcc954e4dfcf40930fee0 Mon Sep 17 00:00:00 2001
From: Peter Lamut <inbox@peterlamut.com>
Date: Wed, 31 Jul 2019 09:39:31 +0200
Subject: [PATCH 2/2] Output BigQuery cell magic error message to stderr

---
 bigquery/google/cloud/bigquery/magics.py | 3 ++-
 bigquery/tests/unit/test_magics.py       | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/bigquery/google/cloud/bigquery/magics.py b/bigquery/google/cloud/bigquery/magics.py
index dc2c0f59278a..2eee7e087f30 100644
--- a/bigquery/google/cloud/bigquery/magics.py
+++ b/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
 
@@ -428,7 +429,7 @@ def _cell_magic(line, query):
         display.clear_output()
 
     if error:
-        print("\nERROR:\n", error)
+        print("\nERROR:\n", error, file=sys.stderr)
         return
 
     result = query_job.to_dataframe(bqstorage_client=bqstorage_client)
diff --git a/bigquery/tests/unit/test_magics.py b/bigquery/tests/unit/test_magics.py
index 93eeb78f2d4c..1a896dda0829 100644
--- a/bigquery/tests/unit/test_magics.py
+++ b/bigquery/tests/unit/test_magics.py
@@ -839,6 +839,7 @@ def test_bigquery_magic_omits_tracebacks_from_error_message():
     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.stdout
+    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