[dagster-dbt] log_columns_in_relation macro to to only log table_sche…

…ma if present (#20088)

## Summary & Motivation

When running the `dbt parse` command on a project like
`dagster-open-platform`, the post hook `log_columns_in_relation` macro
produces many empty log statements. This updates the macro to only log
`table_schema` when it is non-null.

```
make manifest
cd dbt && dbt parse && cd ..
15:24:05  Running with dbt=1.7.6
15:24:09  Registered adapter: snowflake=1.7.1
15:24:09  Unable to do partial parsing because profile has changed
15:24:09  Unable to do partial parsing because a project dependency has been added
15:24:09  Unable to do partial parsing because a project config has changed
15:24:09  {}
15:24:09  {}
15:24:09  {}
15:24:09  {}
15:24:09  {}
15:24:09  {}
15:24:09  {}
15:24:09  {}
```

## How I Tested These Changes

Only tested happy-path by updating the macro in the `dbt_modules`
directory and running the project.

I confirmed that the logs were _not_ produced in my project, but I was
unable to test when they _are_ produced.

---------

Co-authored-by: Rex Ledesma <[email protected]>

python_modules/libraries/dagster-dbt/dagster_dbt_tests/core/dbt_packages/test_columns_metadata.py

@@ -1,4 +1,6 @@
+import json
 import os
+import subprocess
 from typing import Any, Dict, cast
 
 from dagster import (
@@ -74,3 +76,29 @@ def assert_columns_metadata(context: AssetExecutionContext, dbt: DbtCliResource)
     )
 
     assert result.success
+
+
+def test_dbt_cli_no_jinja_log_info() -> None:
+    dbt = DbtCliResource(project_dir=os.fspath(test_metadata_path))
+    dbt_cli_parse_invocation = dbt.cli(["parse"])
+
+    assert dbt_cli_parse_invocation.is_successful()
+    assert not any(
+        event.raw_event["info"]["name"] == "JinjaLogInfo"
+        for event in dbt_cli_parse_invocation.stream_raw_events()
+    )
+
+
+def test_dbt_raw_cli_no_empty_jinja_log_info() -> None:
+    # Ensure `log_columns_in_relation.sql` does not produce empty `{}` statements when run outside of the context of `dagster-dbt`
+    result = subprocess.run(
+        ["dbt", "--log-format", "json", "--no-partial-parse", "parse"],
+        capture_output=True,
+        text=True,
+        cwd=test_metadata_path,
+        check=False,
+    )
+
+    assert not any(
+        [json.loads(line)["info"]["name"] == "JinjaLogInfo" for line in result.stdout.splitlines()]
+    )

python_modules/libraries/dagster-dbt/dbt_packages/dagster/macros/log_columns_in_relation.sql

@@ -7,5 +7,7 @@
         {%- set _ = table_schema.update(serializable_column) -%}
     {% endfor %}
 
-    {% do log(tojson(table_schema), info=true) %}
+    {% if table_schema %}
+        {% do log(tojson(table_schema), info=true) %}
+    {% endif %}
 {% endmacro %}