GH-42213: [Swift] Use "--warnings-as-errors" only on CI

[abandy]

Rationale for this change

Downstream clients are getting a conflicting options error when building with the "-warnings-as-errors" swift option.

What changes are included in this PR?

This PR disables the "-warnings-as-errors" swift options by default and enables them for CI builds only. The Swift CI script will enable the options in the Package.swift files before running the build.

• GitHub Issue: [CI][Swift] Make a Package.swift file specific for CI build to ensure warnings are handles as errors #42213

[github-actions]

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or

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See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview

[assignUser]

Does swift not have a way of passing additional flags to the compiler similar to the CXX_FLAGS envvar in C++? Or is that an issue with dependencies?

[assignUser]

Also fyi: #42212

[abandy]

Does swift not have a way of passing additional flags to the compiler similar to the CXX_FLAGS envvar in C++? Or is that an issue with dependencies?

I did a search but didn't see this as an option. CMake does support Swift (https://github.com/apple/swift-cmake-examples) so maybe we can switch to CMake (in a future PR) the CI build and it might provide a more flexible way to handle this issue.

[kou]

Oh... How about embedding special marks to Package.swift and using it to enable -warnings-as-error in our CI something like the following?

diff --git a/ci/scripts/swift_test.sh b/ci/scripts/swift_test.sh
index b523e3891d..60ea7bde43 100755
--- a/ci/scripts/swift_test.sh
+++ b/ci/scripts/swift_test.sh
@@ -34,7 +34,9 @@ popd
 
 source_dir=${1}/swift/Arrow
 pushd ${source_dir}
+sed -i.bak -e 's,// build: ,,g' Package.swift
 swift test
+mv Package.swift{.bak,}
 popd
 
 source_dir=${1}/swift/ArrowFlight
diff --git a/swift/Arrow/Package.swift b/swift/Arrow/Package.swift
index 6944d7b910..80c7d78e44 100644
--- a/swift/Arrow/Package.swift
+++ b/swift/Arrow/Package.swift
@@ -46,7 +46,7 @@ let package = Package(
             name: "ArrowC",
             path: "Sources/ArrowC",
             swiftSettings: [
-                .unsafeFlags(["-warnings-as-errors"])
+                // build: .unsafeFlags(["-warnings-as-errors"])
             ]
         ),
         .target(
@@ -56,14 +56,14 @@ let package = Package(
                 .product(name: "Atomics", package: "swift-atomics")
             ],
             swiftSettings: [
-                .unsafeFlags(["-warnings-as-errors"])
+                // build: .unsafeFlags(["-warnings-as-errors"])
             ]
         ),
         .testTarget(
             name: "ArrowTests",
             dependencies: ["Arrow", "ArrowC"],
             swiftSettings: [
-                .unsafeFlags(["-warnings-as-errors"])
+                // build: .unsafeFlags(["-warnings-as-errors"])
             ]
         )
     ]

[raulcd]

Oh... How about embedding special marks to Package.swift and using it to enable -warnings-as-error in our CI something like the following?

Or using some environment variable with the "extra flags", I've found this snippet example for what I had in mind: https://gist.github.com/Sorix/21e61347f478ae2e83ef4d8a92d933af

[abandy]

Oh... How about embedding special marks to Package.swift and using it to enable -warnings-as-error in our CI something like the following?

Or using some environment variable with the "extra flags", I've found this snippet example for what I had in mind: https://gist.github.com/Sorix/21e61347f478ae2e83ef4d8a92d933af

I looked at the snippet above. Cool idea but it seems that it won't work for Xcode based on the last comment:
"Xcode scheme env variables are for app run, not for build time, that's why this doesn't work."

[lukedg97]

reposting here to make sure it is seen:

@abandy

I can confirm that I fail to build on main with the error: Conflicting options '-warnings-as-errors' and '-suppress-warnings'

and with the only change being checking out with the command gh pr checkout 42214 i am able to build with no errors

For those who may find this conversation later make sure to right-click on the package in xcode and select the option "Update Package" to make sure that Xcode picks up the change.

Originally posted by @lukedg97 in #42213 (comment)

[kou]

+1

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 7 benchmarking runs that have been run so far on merge-commit 4a54950.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 11 possible false positives for unstable benchmarks that are known to sometimes produce them.