Unexpected resolving behavior for non-exist branch dependency

[Kyle-Ye]

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

We using package(url:branch:) API and specify a non-exist branch (existing as a tag) the package resolution is expected to fail.

eg.

  dependencies: [
      .package(url: "https://github.com/swiftlang/swift-markdown.git", branch: "0.5.0"),
  ],

Expected behavior

Fail with error message - No branch named "0.5.0" can be found on swift-markdown repo.

Actual behavior

Resolve and update Package.resolved file successfully.

  {
    "identity" : "swift-markdown",
    "kind" : "remoteSourceControl",
    "location" : "https://github.com/swiftlang/swift-markdown.git",
    "state" : {
      "branch" : "0.5.0",
      "revision" : "8f79cb175981458a0a27e76cb42fee8e17b1a993"
    }
  },

Steps to reproduce

mkdir DemoKit
cd DemoKit
swift package init
# Update the Package.swift file
vim Package.swift

Add the following code after products

    dependencies: [
        .package(url: "https://github.com/swiftlang/swift-markdown.git", branch: "0.5.0"),
    ],

Swift Package Manager version/commit hash

No response

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

swift-driver version: 1.115.1 Apple Swift version 6.0.3 (swiftlang-6.0.3.1.10 clang-1600.0.30.1)
Target: arm64-apple-macosx15.0
Darwin <redacted>.local 24.2.0 Darwin Kernel Version 24.2.0: Fri Dec  6 18:56:34 PST 2024; root:xnu-11215.61.5~2/RELEASE_ARM64_T6020 arm64