fix: allow default empty vars for conditionals (#2570)

# What does this PR do?

We were not using conditionals correctly, conditionals can only be used
when the env variable is set, so `${env.ENVIRONMENT:+}` would return
None is ENVIRONMENT is not set.

If you want to create a conditional value, you need to do
`${env.ENVIRONMENT:=}`, this will pick the value of ENVIRONMENT if set,
otherwise will return None.

Closes: https://github.com/meta-llama/llama-stack/issues/2564

Signed-off-by: Sébastien Han <seb@redhat.com>

llama_stack/templates/sambanova/run.yaml

@@ -28,15 +28,15 @@ providers:
   - provider_id: ${env.ENABLE_CHROMADB:+chromadb}
     provider_type: remote::chromadb
     config:
-      url: ${env.CHROMADB_URL:+}
+      url: ${env.CHROMADB_URL:=}
   - provider_id: ${env.ENABLE_PGVECTOR:+pgvector}
     provider_type: remote::pgvector
     config:
       host: ${env.PGVECTOR_HOST:=localhost}
       port: ${env.PGVECTOR_PORT:=5432}
-      db: ${env.PGVECTOR_DB:+}
-      user: ${env.PGVECTOR_USER:+}
-      password: ${env.PGVECTOR_PASSWORD:+}
+      db: ${env.PGVECTOR_DB:=}
+      user: ${env.PGVECTOR_USER:=}
+      password: ${env.PGVECTOR_PASSWORD:=}
   safety:
   - provider_id: sambanova
     provider_type: remote::sambanova
@@ -65,12 +65,12 @@ providers:
   - provider_id: brave-search
     provider_type: remote::brave-search
     config:
-      api_key: ${env.BRAVE_SEARCH_API_KEY:+}
+      api_key: ${env.BRAVE_SEARCH_API_KEY:=}
       max_results: 3
   - provider_id: tavily-search
     provider_type: remote::tavily-search
     config:
-      api_key: ${env.TAVILY_SEARCH_API_KEY:+}
+      api_key: ${env.TAVILY_SEARCH_API_KEY:=}
       max_results: 3
   - provider_id: rag-runtime
     provider_type: inline::rag-runtime
@@ -81,7 +81,7 @@ providers:
   - provider_id: wolfram-alpha
     provider_type: remote::wolfram-alpha
     config:
-      api_key: ${env.WOLFRAM_ALPHA_API_KEY:+}
+      api_key: ${env.WOLFRAM_ALPHA_API_KEY:=}
 metadata_store:
   type: sqlite
   db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/sambanova}/registry.db

llama_stack/templates/sambanova/sambanova.py

@@ -75,15 +75,15 @@ def get_distribution_template() -> DistributionTemplate:
         Provider(
             provider_id="${env.ENABLE_CHROMADB:+chromadb}",
             provider_type="remote::chromadb",
-            config=ChromaVectorIOConfig.sample_run_config(url="${env.CHROMADB_URL:+}"),
+            config=ChromaVectorIOConfig.sample_run_config(url="${env.CHROMADB_URL:=}"),
         ),
         Provider(
             provider_id="${env.ENABLE_PGVECTOR:+pgvector}",
             provider_type="remote::pgvector",
             config=PGVectorVectorIOConfig.sample_run_config(
-                db="${env.PGVECTOR_DB:+}",
-                user="${env.PGVECTOR_USER:+}",
-                password="${env.PGVECTOR_PASSWORD:+}",
+                db="${env.PGVECTOR_DB:=}",
+                user="${env.PGVECTOR_USER:=}",
+                password="${env.PGVECTOR_PASSWORD:=}",
             ),
         ),
     ]