build(deps): bump docker/setup-buildx-action from 3 to 4

Bumps [docker/setup-buildx-action](https://github.com/docker/setup-buildx-action) from 3 to 4.
- [Release notes](https://github.com/docker/setup-buildx-action/releases)
- [Commits](https://github.com/docker/setup-buildx-action/compare/v3...v4)

---
updated-dependencies:
- dependency-name: docker/setup-buildx-action
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/release-image.yml

@@ -30,7 +30,7 @@ jobs:
         uses: docker/setup-qemu-action@v3
 
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
+        uses: docker/setup-buildx-action@v4
 
       - name: Log in to GHCR
         uses: docker/login-action@v3

README.md

@@ -39,7 +39,7 @@ uv sync
 
 3. Choose a gateway profile:
 - `config/gateway.yaml` targets a locally running companion backend on `127.0.0.1:8068`.
-- `config/gateway.container.yaml` uses `GATEWAY_UPSTREAM_HOST` for host-container networking and defaults to `host.docker.internal` (set `GATEWAY_UPSTREAM_HOST=host.containers.internal` for Podman), with default `gateway_port: 8067`.
+- `config/gateway.container.yaml` targets the companion backend inside the bundled compose network, with default `gateway_port: 8067`.
 4. Run the gateway with the managed environment:
 
 ```bash
@@ -215,7 +215,6 @@ make stop
 - `CONTAINER_ENGINE=docker` (or `podman`)
 - `PORT=8067`
 - `GATEWAY_PORT=8067`
-- `GATEWAY_UPSTREAM_HOST=host.docker.internal` (set to `host.containers.internal` for Podman host networking)
 - `IMAGE_NAME=openapi-api-gateway`
 - `IMAGE_TAG=latest`
 - `ENV_FILE=.env`

config/gateway.container.yaml

@@ -13,7 +13,7 @@ settings:
 
 upstreams:
   lta_datamall:
-    base_url: http://${GATEWAY_UPSTREAM_HOST:-host.docker.internal}/
+    base_url: http://host.containers.internal/
     port: 8068
     timeout_seconds: 20
 

src/gateway_framework/config.py

@@ -1,9 +1,6 @@
 from __future__ import annotations
 
-import os
-import re
 from pathlib import Path
-from typing import Any
 from typing import Literal
 from urllib.parse import urlsplit, urlunsplit
 
@@ -90,32 +87,6 @@ class GatewayConfig(BaseModel):
     routes: list[RouteConfig]
 
 
-_ENV_PLACEHOLDER_PATTERN = re.compile(r"\$\{([A-Za-z_][A-Za-z0-9_]*)(?::-([^}]*))?\}")
-
-
-def _expand_env_placeholders(value: str) -> str:
-    def replacer(match: re.Match[str]) -> str:
-        var_name = match.group(1)
-        default_value = match.group(2)
-        if var_name in os.environ:
-            return os.environ[var_name]
-        if default_value is not None:
-            return default_value
-        raise ValueError(f"Missing required environment variable: {var_name}")
-
-    return _ENV_PLACEHOLDER_PATTERN.sub(replacer, value)
-
-
-def _resolve_env_placeholders(value: Any) -> Any:
-    if isinstance(value, str):
-        return _expand_env_placeholders(value)
-    if isinstance(value, list):
-        return [_resolve_env_placeholders(item) for item in value]
-    if isinstance(value, dict):
-        return {key: _resolve_env_placeholders(item) for key, item in value.items()}
-    return value
-
-
 def load_gateway_config(config_path: str | Path) -> GatewayConfig:
     path = Path(config_path)
     if not path.exists():
@@ -125,8 +96,6 @@ def load_gateway_config(config_path: str | Path) -> GatewayConfig:
     if not isinstance(raw, dict):
         raise ValueError("Gateway config must be a YAML object")
 
-    raw = _resolve_env_placeholders(raw)
-
     try:
         config = GatewayConfig.model_validate(raw)
     except ValidationError as exc:

tests/test_config.py

@@ -74,68 +74,6 @@ routes:
         load_gateway_config(config_file)
 
 
-def test_load_gateway_config_expands_env_with_default(tmp_path, monkeypatch) -> None:
-    monkeypatch.delenv("GATEWAY_UPSTREAM_HOST", raising=False)
-    config_file = tmp_path / "gateway.yaml"
-    config_file.write_text(
-        """
-upstreams:
-  demo:
-    base_url: http://${GATEWAY_UPSTREAM_HOST:-host.docker.internal}/
-routes:
-  - path: /api/v1/demo
-    methods: [GET]
-    upstream: demo
-""".strip(),
-        encoding="utf-8",
-    )
-
-    config = load_gateway_config(config_file)
-
-    assert str(config.upstreams["demo"].base_url) == "http://host.docker.internal/"
-
-
-def test_load_gateway_config_expands_env_override(tmp_path, monkeypatch) -> None:
-    monkeypatch.setenv("GATEWAY_UPSTREAM_HOST", "host.containers.internal")
-    config_file = tmp_path / "gateway.yaml"
-    config_file.write_text(
-        """
-upstreams:
-  demo:
-    base_url: http://${GATEWAY_UPSTREAM_HOST:-host.docker.internal}/
-routes:
-  - path: /api/v1/demo
-    methods: [GET]
-    upstream: demo
-""".strip(),
-        encoding="utf-8",
-    )
-
-    config = load_gateway_config(config_file)
-
-    assert str(config.upstreams["demo"].base_url) == "http://host.containers.internal/"
-
-
-def test_load_gateway_config_missing_required_env_var_raises(tmp_path, monkeypatch) -> None:
-    monkeypatch.delenv("GATEWAY_UPSTREAM_HOST", raising=False)
-    config_file = tmp_path / "gateway.yaml"
-    config_file.write_text(
-        """
-upstreams:
-  demo:
-    base_url: http://${GATEWAY_UPSTREAM_HOST}/
-routes:
-  - path: /api/v1/demo
-    methods: [GET]
-    upstream: demo
-""".strip(),
-        encoding="utf-8",
-    )
-
-    with pytest.raises(ValueError, match="Missing required environment variable"):
-        load_gateway_config(config_file)
-
-
 def test_sample_gateway_config_matches_companion_backend_route_set() -> None:
   config = load_gateway_config(Path("config/gateway.yaml"))