Don't make people set the same value in two variables (datacontract#246)

README.md

@@ -390,7 +390,7 @@ models:
 
 | Environment Variable                         | Example                   | Description                                             |
 |----------------------------------------------|---------------------------|---------------------------------------------------------|
-| `DATACONTRACT_BIGQUERY_ACCOUNT_INFO_JSON_PATH` | `~/service-access-key.json` | Service Access key as saved on key creation by BigQuery |
+| `DATACONTRACT_BIGQUERY_ACCOUNT_INFO_JSON_PATH` | `~/service-access-key.json` | Service Access key as saved on key creation by BigQuery. If this environment variable isn't set, the cli tries to use `GOOGLE_APPLICATION_CREDENTIALS` as a fallback, so if you have that set for using their Python library anyway, it should work seamlessly. |
 
 
 

datacontract/engines/soda/connections/bigquery.py

@@ -6,10 +6,17 @@
 # https://docs.soda.io/soda/connect-bigquery.html#authentication-methods
 def to_bigquery_soda_configuration(server):
     # with service account key, using an external json file
+
+    # check for our own environment variable first
+    account_info = os.getenv("DATACONTRACT_BIGQUERY_ACCOUNT_INFO_JSON_PATH")
+    if account_info is None:
+        # but as a fallback look for the default google one
+        account_info = os.getenv("GOOGLE_APPLICATION_CREDENTIALS")
+
     soda_configuration = {
         f"data_source {server.type}": {
             "type": "bigquery",
-            "account_info_json_path": os.getenv("DATACONTRACT_BIGQUERY_ACCOUNT_INFO_JSON_PATH"),
+            "account_info_json_path": account_info,
             "auth_scopes": ["https://www.googleapis.com/auth/bigquery"],
             "project_id": server.project,
             "dataset": server.dataset,