"swift build" command duplicates error messages

[Stiivi]

Description
swift build command prints the same error multiple times. Example output:

% swift build
Building for debugging...
error: emit-module command failed with exit code 1 (use -v to see invocation)
/home/stefan/Dupe/Sources/Dupe/Dupe.swift:4:9: error: consecutive statements on a line must be separated by ';'
let this is error
        ^
        ;
/home/stefan/Dupe/Sources/Dupe/Dupe.swift:4:10: error: expected expression
let this is error
         ^
/home/stefan/Dupe/Sources/Dupe/Dupe.swift:4:5: error: type annotation missing in pattern
let this is error
    ^
/home/stefan/Dupe/Sources/Dupe/Dupe.swift:4:9: error: consecutive statements on a line must be separated by ';'
let this is error
        ^
        ;
/home/stefan/Dupe/Sources/Dupe/Dupe.swift:4:10: error: expected expression
let this is error
         ^
/home/stefan/Dupe/Sources/Dupe/Dupe.swift:4:5: error: type annotation missing in pattern
let this is error
    ^
error: fatalError

EDIT: In one of my projects (can't share the source) the error has been duplicated 16 times.

Steps to reproduce

1. Create a new package:
   • mkdir Dupe
   • cd Dupe
   • swift package init
2. Create an erroneous source file:
   • echo "let this is error" > Sources/Dupe/Dupe.swift
3. Run swift build

Expected behavior

Each error is displayed only once.

[AnthonyLatsis]

Shorter — swiftc -emit-module -enable-batch-mode Dupe.swift where Dupe.swift contains anything that must not parse, e.g. let. The culprit is -enable-batch-mode and the duplication does not reproduce with the old driver.

@hamishknight Please see to the transfer.

[hamishknight]

Interesting, we appear to be creating two -emit-module jobs, one of them seems like an intermediate output that would have previously been used for merge-modules (or I guess maybe it's still required to ensure we type-check function bodies?):

❯ ./swiftc -emit-module -enable-batch-mode ~/src/swift-test-arena/swift-test-arena/main.swift -###
/Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-frontend -frontend -emit-module -primary-file /Users/hamish/src/swift-test-arena/swift-test-arena/main.swift -target x86_64-apple-macosx13.0 -warn-on-potentially-unavailable-enum-case -enable-objc-interop -color-diagnostics -new-driver-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-driver -empty-abi-descriptor -resource-dir /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift -module-name main -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift/host/plugins -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/local/lib/swift/host/plugins -o /var/folders/3m/l5fbv4dn6wz112cw2nhjq69h0000gn/T/TemporaryDirectory.jKvDlg/main-2.swiftmodule
/Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-frontend -frontend -emit-module -experimental-skip-non-inlinable-function-bodies-without-types /Users/hamish/src/swift-test-arena/swift-test-arena/main.swift -target x86_64-apple-macosx13.0 -warn-on-potentially-unavailable-enum-case -enable-objc-interop -color-diagnostics -new-driver-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-driver -empty-abi-descriptor -resource-dir /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift -module-name main -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift/host/plugins -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/local/lib/swift/host/plugins -emit-module-doc-path main.swiftdoc -emit-module-source-info-path main.swiftsourceinfo -o main.swiftmodule -emit-abi-descriptor-path main.abi.json

❯ ./swiftc -enable-batch-mode -emit-module ~/src/swift-test-arena/swift-test-arena/main.swift -v
Swift version 5.9-dev (LLVM dcb09f599ae5aa9, Swift edc003ac9278d7c)
Target: x86_64-apple-macosx13.0
/Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-frontend -frontend -emit-module -primary-file /Users/hamish/src/swift-test-arena/swift-test-arena/main.swift -target x86_64-apple-macosx13.0 -warn-on-potentially-unavailable-enum-case -enable-objc-interop -color-diagnostics -new-driver-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-driver -empty-abi-descriptor -resource-dir /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift -module-name main -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift/host/plugins -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/local/lib/swift/host/plugins -o /var/folders/3m/l5fbv4dn6wz112cw2nhjq69h0000gn/T/TemporaryDirectory.lfL6bi/main-2.swiftmodule
/Users/hamish/src/swift-test-arena/swift-test-arena/main.swift:2365:4: error: expected pattern
var
   ^
/Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-frontend -frontend -emit-module -experimental-skip-non-inlinable-function-bodies-without-types /Users/hamish/src/swift-test-arena/swift-test-arena/main.swift -target x86_64-apple-macosx13.0 -warn-on-potentially-unavailable-enum-case -enable-objc-interop -color-diagnostics -new-driver-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-driver -empty-abi-descriptor -resource-dir /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift -module-name main -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift/host/plugins -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/local/lib/swift/host/plugins -emit-module-doc-path main.swiftdoc -emit-module-source-info-path main.swiftsourceinfo -o main.swiftmodule -emit-abi-descriptor-path main.abi.json
error: emit-module command failed with exit code 1 (use -v to see invocation)
/Users/hamish/src/swift-test-arena/swift-test-arena/main.swift:2365:4: error: expected pattern
var
   ^
error: fatalError

Without -enable-batch-mode, we appear to do the same thing, but the jobs are the other way around, and we appear to bail after the first failure:

❯ ./swiftc -emit-module ~/src/swift-test-arena/swift-test-arena/main.swift -###
/Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-frontend -frontend -emit-module -experimental-skip-non-inlinable-function-bodies-without-types /Users/hamish/src/swift-test-arena/swift-test-arena/main.swift -target x86_64-apple-macosx13.0 -warn-on-potentially-unavailable-enum-case -enable-objc-interop -color-diagnostics -new-driver-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-driver -empty-abi-descriptor -resource-dir /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift -module-name main -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift/host/plugins -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/local/lib/swift/host/plugins -emit-module-doc-path main.swiftdoc -emit-module-source-info-path main.swiftsourceinfo -o main.swiftmodule -emit-abi-descriptor-path main.abi.json
/Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-frontend -frontend -emit-module -primary-file /Users/hamish/src/swift-test-arena/swift-test-arena/main.swift -target x86_64-apple-macosx13.0 -warn-on-potentially-unavailable-enum-case -enable-objc-interop -color-diagnostics -new-driver-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-driver -empty-abi-descriptor -resource-dir /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift -module-name main -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift/host/plugins -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/local/lib/swift/host/plugins -o /var/folders/3m/l5fbv4dn6wz112cw2nhjq69h0000gn/T/TemporaryDirectory.TqvOsn/main-1.swiftmodule

❯ ./swiftc -emit-module ~/src/swift-test-arena/swift-test-arena/main.swift -v
Swift version 5.9-dev (LLVM dcb09f599ae5aa9, Swift edc003ac9278d7c)
Target: x86_64-apple-macosx13.0
/Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-frontend -frontend -emit-module -experimental-skip-non-inlinable-function-bodies-without-types /Users/hamish/src/swift-test-arena/swift-test-arena/main.swift -target x86_64-apple-macosx13.0 -warn-on-potentially-unavailable-enum-case -enable-objc-interop -color-diagnostics -new-driver-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/bin/swift-driver -empty-abi-descriptor -resource-dir /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift -module-name main -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/lib/swift/host/plugins -plugin-path /Users/hamish/src/swift-dev/build/Release/swift-macosx-x86_64/local/lib/swift/host/plugins -emit-module-doc-path main.swiftdoc -emit-module-source-info-path main.swiftsourceinfo -o main.swiftmodule -emit-abi-descriptor-path main.abi.json
error: emit-module command failed with exit code 1 (use -v to see invocation)
/Users/hamish/src/swift-test-arena/swift-test-arena/main.swift:2365:4: error: expected pattern
var
   ^
error: fatalError

[artemcm]

Ugh.
https://github.com/apple/swift-driver/blob/main/Sources/SwiftDriver/Jobs/Planning.swift#L456

[cpisciotta]

Hi @artemcm. I'm seeing a similar issue with xcodebuild and an Xcode project. Is this likely the same issue? Should I file a separate GitHub issue? I already filed a TSI and FB report with the logs for reference.

[artemcm]

@cpisciotta could you please post the FB number here?

[cpisciotta]

@artemcm FB12568959

[cpisciotta]

Hey, @artemcm! Just checking in...

• Should I assume the root cause of this issue is the same as the one I see with xcodebuild? If not, should I create a new GitHub issue?
• Is there any additional context I can provide to help investigate a fix for this issue?

[cpisciotta]

Hey, @artemcm. Checking in on this again...

Is there any progress or update on this issue? It's causing some issues for my team when we use xcodebuild. It'd be helpful to set expectations about the priority and timeline for a possible fix.