Merge pull request #3097 from freqtrade/parse_config_error

Improve config parse error handling

freqtrade/configuration/load_config.py

@@ -1,13 +1,15 @@
 """
 This module contain functions to load the configuration file
 """
-import rapidjson
 import logging
+import re
 import sys
+from pathlib import Path
 from typing import Any, Dict
 
-from freqtrade.exceptions import OperationalException
+import rapidjson
 
+from freqtrade.exceptions import OperationalException
 
 logger = logging.getLogger(__name__)
 
@@ -15,6 +17,26 @@ logger = logging.getLogger(__name__)
 CONFIG_PARSE_MODE = rapidjson.PM_COMMENTS | rapidjson.PM_TRAILING_COMMAS
 
 
+def log_config_error_range(path: str, errmsg: str) -> str:
+    """
+    Parses configuration file and prints range around error
+    """
+    if path != '-':
+        offsetlist = re.findall(r'(?<=Parse\serror\sat\soffset\s)\d+', errmsg)
+        if offsetlist:
+            offset = int(offsetlist[0])
+            text = Path(path).read_text()
+            # Fetch an offset of 80 characters around the error line
+            subtext = text[offset-min(80, offset):offset+80]
+            segments = subtext.split('\n')
+            if len(segments) > 3:
+                # Remove first and last lines, to avoid odd truncations
+                return '\n'.join(segments[1:-1])
+            else:
+                return subtext
+    return ''
+
+
 def load_config_file(path: str) -> Dict[str, Any]:
     """
     Loads a config file from the given path
@@ -29,5 +51,12 @@ def load_config_file(path: str) -> Dict[str, Any]:
         raise OperationalException(
             f'Config file "{path}" not found!'
             ' Please create a config file or check whether it exists.')
+    except rapidjson.JSONDecodeError as e:
+        err_range = log_config_error_range(path, str(e))
+        raise OperationalException(
+            f'{e}\n'
+            f'Please verify the following segment of your configuration:\n{err_range}'
+            if err_range else 'Please verify your configuration file for syntax errors.'
+        )
 
     return config

tests/test_configuration.py

@@ -18,7 +18,7 @@ from freqtrade.configuration.config_validation import validate_config_schema
 from freqtrade.configuration.deprecated_settings import (
     check_conflicting_settings, process_deprecated_setting,
     process_temporary_deprecated_settings)
-from freqtrade.configuration.load_config import load_config_file
+from freqtrade.configuration.load_config import load_config_file, log_config_error_range
 from freqtrade.constants import DEFAULT_DB_DRYRUN_URL, DEFAULT_DB_PROD_URL
 from freqtrade.exceptions import OperationalException
 from freqtrade.loggers import _set_loggers, setup_logging
@@ -66,6 +66,30 @@ def test_load_config_file(default_conf, mocker, caplog) -> None:
     assert validated_conf.items() >= default_conf.items()
 
 
+def test_load_config_file_error(default_conf, mocker, caplog) -> None:
+    del default_conf['user_data_dir']
+    filedata = json.dumps(default_conf).replace(
+        '"stake_amount": 0.001,', '"stake_amount": .001,')
+    mocker.patch('freqtrade.configuration.load_config.open', mocker.mock_open(read_data=filedata))
+    mocker.patch.object(Path, "read_text", MagicMock(return_value=filedata))
+
+    with pytest.raises(OperationalException, match=f".*Please verify the following segment.*"):
+        load_config_file('somefile')
+
+
+def test_load_config_file_error_range(default_conf, mocker, caplog) -> None:
+    del default_conf['user_data_dir']
+    filedata = json.dumps(default_conf).replace(
+        '"stake_amount": 0.001,', '"stake_amount": .001,')
+    mocker.patch.object(Path, "read_text", MagicMock(return_value=filedata))
+
+    x = log_config_error_range('somefile', 'Parse error at offset 64: Invalid value.')
+    assert isinstance(x, str)
+    assert (x == '{"max_open_trades": 1, "stake_currency": "BTC", '
+            '"stake_amount": .001, "fiat_display_currency": "USD", '
+            '"ticker_interval": "5m", "dry_run": true, ')
+
+
 def test__args_to_config(caplog):
 
     arg_list = ['trade', '--strategy-path', 'TestTest']