[SwiftBuild] SwiftPM does not incrementally build when embedded resource files are modified

[bkhouri]

Is it reproducible with SwiftPM command-line tools: swift build, swift test, swift package etc?

• Confirmed reproduction steps with SwiftPM CLI. The description text must include reproduction steps with either of command-line SwiftPM commands, swift build, swift test, swift package etc.

Description

When only a resource file that is embedded in Swift source code is modified, SwiftPM does not rebuild the targets when using SwiftBuild.

Expected behavior

The resource files are considered as inputs to the build graph, causing modification of a resource file to rebuild the appropriate pieces.

Actual behavior

An incremental rebuild does not occur

Steps to reproduce

Option 1:
Search for this GitHub issue in swiftpm code base

Option 2:

1. checkout swiftpm
2. Run the following

❯ swift build  --package-path ./Fixtures/Resources/EmbedInCodeSimple --build-system swiftbuild

❯ $(swift build --show-bin-path --package-path ./Fixtures/Resources/EmbedInCodeSimple)/EmbedInCodeSimple  

❯ echo "This is a new message" > ./Fixtures/Resources/EmbedInCodeSimple/Sources/EmbedInCodeSimple/best.txt

❯ swift build  --package-path ./Fixtures/Resources/EmbedInCodeSimple --build-system swiftbuild

❯ $(swift build --show-bin-path --package-path ./Fixtures/Resources/EmbedInCodeSimple)/EmbedInCodeSimple  

❯ # We expect the new output here

❯ swift package clean --package-path ./Fixtures/Resources/EmbedInCodeSimple)

❯ swift build  --package-path ./Fixtures/Resources/EmbedInCodeSimple --build-system swiftbuild

❯ $(swift build --show-bin-path --package-path ./Fixtures/Resources/EmbedInCodeSimple)/EmbedInCodeSimple  
# This outputs the expected test

Swift Package Manager version/commit hash

branch main (commit ID 52f7c417c2949d9aadd950169c4ae3ab4a74f31c)

Swift & OS version (output of swift --version ; uname -a)

No response

[Viditgupta-official]

I can confirm this is reproducible with SwiftPM CLI using a minimal standalone package.

Setup:

Single library target

Embedded resource via .process("Resources")

Repro steps:

swift build (initial build emits module)

Modify only the embedded resource file

Run swift build again

Observed:

No target rebuild occurs (only swift-version file is written)

Expected:

Resource-only changes should be treated as build inputs and trigger a rebuild

This appears to be an incremental build graph issue in the SwiftBuild backend rather than package layout.