Fix docker discovery for bigquery adapter

Author: Maxteabag

sqlit/domains/connections/providers/bigquery/adapter.py

@@ -127,7 +127,16 @@ def connect(self, config: ConnectionConfig) -> BigQueryConnection:
         credentials = None
         client_options = None
 
+        # Check for emulator: either via env var or by detecting a port in config
+        # (BigQuery doesn't normally use TCP, so any port means emulator)
         emulator_host = os.environ.get("BIGQUERY_EMULATOR_HOST")
+        endpoint = config.tcp_endpoint
+        if not emulator_host and endpoint and endpoint.port:
+            # Any port specified means we're connecting to an emulator
+            # Default to localhost if no explicit host for emulator
+            host = "localhost"
+            emulator_host = f"http://{host}:{endpoint.port}"
+
         if emulator_host:
             if not emulator_host.startswith("http"):
                 emulator_host = f"http://{emulator_host}"

sqlit/domains/connections/providers/bigquery/provider.py

@@ -1,28 +1,62 @@
 """Provider registration."""
 
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
 from sqlit.domains.connections.providers.adapter_provider import build_adapter_provider
 from sqlit.domains.connections.providers.bigquery.schema import SCHEMA
 from sqlit.domains.connections.providers.catalog import register_provider
+from sqlit.domains.connections.providers.docker import DockerCredentials, DockerDetector
 from sqlit.domains.connections.providers.model import DatabaseProvider, ProviderSpec
 
+if TYPE_CHECKING:
+    from collections.abc import Mapping
+
 
 def _provider_factory(spec: ProviderSpec) -> DatabaseProvider:
     from sqlit.domains.connections.providers.bigquery.adapter import BigQueryAdapter
 
     return build_adapter_provider(spec, SCHEMA, BigQueryAdapter())
 
+
+def _bigquery_docker_post_process(
+    creds: DockerCredentials, env_vars: Mapping[str, str]
+) -> DockerCredentials:
+    """Extract project ID from emulator command args or use default."""
+    # The emulator typically uses --project flag, but env vars take precedence
+    # Default to 'test-project' which is common for local development
+    return DockerCredentials(
+        user=creds.user,
+        password=creds.password,
+        database=env_vars.get("BIGQUERY_DATASET", creds.database) or "test_sqlit",
+    )
+
+
 SPEC = ProviderSpec(
     db_type="bigquery",
     display_name="Google BigQuery",
     schema_path=("sqlit.domains.connections.providers.bigquery.schema", "SCHEMA"),
     supports_ssh=False,
     is_file_based=False,
     has_advanced_auth=True,
-    default_port="",
+    default_port="9050",
     requires_auth=False,
     badge_label="BQ",
     url_schemes=("bigquery",),
     provider_factory=_provider_factory,
+    docker_detector=DockerDetector(
+        image_patterns=("bigquery-emulator", "goccy/bigquery-emulator"),
+        env_vars={
+            "user": (),
+            "password": (),
+            "database": ("BIGQUERY_DATASET",),
+        },
+        default_user="",
+        default_database="test_sqlit",
+        preferred_host="test-project",  # Use as project ID, not actual host
+        post_process=_bigquery_docker_post_process,
+    ),
 )
 
 register_provider(SPEC)

sqlit/domains/connections/providers/bigquery/schema.py

@@ -31,6 +31,13 @@ def _bigquery_auth_is_service_account(config: dict[str, str]) -> bool:
             required=False,
             description="GCP Project ID (or infer from environment)",
         ),
+        SchemaField(
+            name="port",
+            label="Emulator Port",
+            placeholder="9050",
+            required=False,
+            description="Port for local BigQuery emulator (leave empty for real BigQuery)",
+        ),
         SchemaField(
             name="database",
             label="Dataset",