Incremental builds with Swift Package Manager and Linux / Docker

Using Swift
20

FWIW, I use --mount=type=cache in my docker builds and had zero issues with it so far.

I was worried that I would need to clear the caches all the time because swift build would get confused and require a clean build - but so far it has been quite the soldier. after ~300 changes/builds I had to clear the caches exactly once (after switching git branches)

here is an excerpt of what I use:

ARG SWIFT_VERSION=5.8

FROM swift:$SWIFT_VERSION AS builder
WORKDIR /build

# Resolve all dependencies if there was a change
COPY ./Package.* ./
RUN --mount=type=cache,target=/build/.build swift package resolve

# Copy all sources and build all
COPY . .

# build with caching and copy app out of cached folder
RUN --mount=type=cache,target=/build/.build \
   swift build -c release \
   && cp -a .build/release/ /release


FROM swift:$SWIFT_VERSION-slim

COPY --from=builder /release/${SERVICE_NAME} ./app
ENTRYPOINT ["./app"]
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