fix: surface WARNING/ERROR logs by default instead of suppressing them

[jschoedl]

Problem

Every CLI command calls enable_debug_logging(debug) as its first action. When --debug is off, that function added a logging.NullHandler to the root logger, which disables Python's lastResort handler — so all logging.warning/logging.error calls in the codebase were silent by default.

The primary output of each command was unaffected (it goes through the rich console on stdout), but the logging-channel diagnostics were lost, e.g.:

datacontract import sql --source t.sql --dialect postgres            # no warning shown
datacontract import sql --source t.sql --dialect postgres --debug    # warning appears on stderr

The sql_importer "placeholder connection values" warning (and resolve.py / excel_importer / spark_importer warnings) only appeared with --debug.

Fix

enable_debug_logging now defaults the root level to WARNING on stderr (so stdout stays clean for piped import/export YAML), and raises it to DEBUG with --debug. Noisy third-party loggers (snowflake.connector, py4j, pyspark, urllib3, soda) are pinned to ERROR to preserve the original intent of the NullHandler (muting library chatter) without blanket-suppressing everything.

Why test/ci/lint are gated

Run.log_info/warn/error deliberately emit to two sinks: the structured run.logs record (rendered to the console, exported to JUnit, published) and stdlib logging (the live stream, and the only output for library callers of DataContract(...).test()). For test/ci/lint, which render run.logs to the console themselves, un-suppressing stderr would print the same WARNING/ERROR twice. Those three commands therefore pass otherwise_disable_stderr=True to keep the old NullHandler behavior. Commands that don't render run.logs (import, export, changelog, catalog, dbt, publish) get the WARNING-on-stderr default — a clean win with no duplication.

Verification

Ran every command before/after, capturing stdout and stderr separately:

• import sql: warning now on stderr; piped stdout YAML stays clean (warning not in the file).
• lint/test/ci: failure/warnings shown once (on stdout, as before) — no doubling on stderr.
• --debug: WARNING/ERROR/DEBUG still on stderr for all commands.
• Test suite: 743 passed, 13 skipped (the only errors are Docker-unavailable integration tests, unrelated).

🤖 Generated with Claude Code