Separate OpenAPI document generation from build-env stage

Signed-off-by: Yasumasa Suenaga <[email protected]>

src/CarbonAware.WebApi/src/Dockerfile

@@ -1,24 +1,33 @@
+# For OpenAPI document
+FROM --platform=$BUILDPLATFORM mcr.microsoft.com/dotnet/sdk:8.0 AS openapi-env
+WORKDIR /app
+ENV DOTNET_ROLL_FORWARD LatestMajor
+COPY . ./
+RUN dotnet build CarbonAware.WebApi/src/CarbonAware.WebApi.csproj -o build
+WORKDIR /app/CarbonAware.WebApi/src
+RUN dotnet tool restore && \
+    dotnet tool run swagger tofile --output /app/build/swagger.yaml --yaml /app/build/CarbonAware.WebApi.dll v1
+
+
+# Builder
 FROM --platform=$BUILDPLATFORM mcr.microsoft.com/dotnet/sdk:8.0 AS build-env
 ARG TARGETARCH
 WORKDIR /app
-
 ENV DOTNET_ROLL_FORWARD LatestMajor
 # Copy everything from source
 COPY . ./
 # Use implicit restore to build and publish
 RUN dotnet publish CarbonAware.WebApi/src/CarbonAware.WebApi.csproj -a $TARGETARCH -o publish
-# Generate OpenAPI spec
-WORKDIR /app/CarbonAware.WebApi/src
-RUN dotnet tool restore && \
-    mkdir -p /app/publish/wwwroot/api/v1 && \
-    dotnet tool run swagger tofile --output /app/publish/wwwroot/api/v1/swagger.yaml --yaml /app/publish/CarbonAware.WebApi.dll v1
+
 
 # Build runtime image
 FROM mcr.microsoft.com/dotnet/aspnet:8.0
 # Install curl for health check
 RUN apt-get update && \
     apt-get install -y --no-install-recommends curl
-# Copy artifacts from build-env
+# Copy artifacts
 WORKDIR /app
 COPY --from=build-env /app/publish .
+RUN mkdir -p /app/wwwroot/api/v1
+COPY --from=openapi-env /app/build/swagger.yaml /app/wwwroot/api/v1/
 ENTRYPOINT ["dotnet", "CarbonAware.WebApi.dll"]