From eae103a82b92949189cf718794d2ad0424005460 Mon Sep 17 00:00:00 2001
From: Simon Willison <swillison@gmail.com>
Date: Fri, 4 Dec 2020 21:21:11 -0800
Subject: [PATCH] Write errors to stderr, closes #1131

---
 datasette/database.py   | 10 ++++++----
 datasette/renderer.py   |  1 -
 datasette/views/base.py |  4 +++-
 tests/test_cli.py       |  7 +++++++
 4 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/datasette/database.py b/datasette/database.py
index 71c45ba0..412e0c59 100644
--- a/datasette/database.py
+++ b/datasette/database.py
@@ -1,8 +1,8 @@
 import asyncio
-import contextlib
 from pathlib import Path
 import janus
 import queue
+import sys
 import threading
 import uuid
 
@@ -104,7 +104,8 @@ class Database:
                 try:
                     result = task.fn(conn)
                 except Exception as e:
-                    print(e)
+                    sys.stderr.write("{}\n".format(e))
+                    sys.stderr.flush()
                     result = e
             task.reply_queue.sync_q.put(result)
 
@@ -156,11 +157,12 @@ class Database:
                     if e.args == ("interrupted",):
                         raise QueryInterrupted(e, sql, params)
                     if log_sql_errors:
-                        print(
-                            "ERROR: conn={}, sql = {}, params = {}: {}".format(
+                        sys.stderr.write(
+                            "ERROR: conn={}, sql = {}, params = {}: {}\n".format(
                                 conn, repr(sql), params, e
                             )
                         )
+                        sys.stderr.flush()
                     raise
 
             if truncate:
diff --git a/datasette/renderer.py b/datasette/renderer.py
index d779b44f..258199fc 100644
--- a/datasette/renderer.py
+++ b/datasette/renderer.py
@@ -20,7 +20,6 @@ def convert_specific_columns_to_json(rows, columns, json_cols):
                 try:
                     value = json.loads(value)
                 except (TypeError, ValueError) as e:
-                    print(e)
                     pass
             new_row.append(value)
         new_rows.append(new_row)
diff --git a/datasette/views/base.py b/datasette/views/base.py
index a93a6378..b8860b74 100644
--- a/datasette/views/base.py
+++ b/datasette/views/base.py
@@ -2,6 +2,7 @@ import asyncio
 import csv
 import hashlib
 import re
+import sys
 import time
 import urllib
 
@@ -362,7 +363,8 @@ class DataView(BaseView):
                                     new_row.append(cell)
                             await writer.writerow(new_row)
                 except Exception as e:
-                    print("caught this", e)
+                    sys.stderr.write("Caught this error: {}\n".format(e))
+                    sys.stderr.flush()
                     await r.write(str(e))
                     return
 
diff --git a/tests/test_cli.py b/tests/test_cli.py
index c52960fb..a0ac7d7a 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -214,3 +214,10 @@ def test_config_deprecated(ensure_eventloop):
     assert result.exit_code == 0
     assert not json.loads(result.output)["allow_download"]
     assert "will be deprecated in" in result.stderr
+
+
+def test_sql_errors_logged_to_stderr(ensure_eventloop):
+    runner = CliRunner(mix_stderr=False)
+    result = runner.invoke(cli, ["--get", "/:memory:.json?sql=select+blah"])
+    assert result.exit_code == 1
+    assert "sql = 'select blah', params = {}: no such column: blah\n" in result.stderr