Bug: Target merging fails when using swift_library dependency directly in rules_ios framework target

[luispadron]

Description

Given the following BUILD file:

load(
    "@build_bazel_rules_ios//rules:framework.bzl",
    rules_ios_apple_framework = "apple_framework",
)
load(
    "@build_bazel_rules_ios//rules:test.bzl",
    rules_ios_unit_test = "ios_unit_test",
)
load(
    "@build_bazel_rules_swift//swift:swift.bzl",
    "swift_library",
    "swift_library_group",
)

rules_ios_apple_framework(
    name = "LibTwo",
    srcs = ["Sources/LibTwo.swift"],
    platforms = {"ios": "15.0"},
    deps = [
        ":External",
    ],
    visibility = ["@rules_xcodeproj//xcodeproj:generated"],
)

rules_ios_unit_test(
    name = "LibTwoTests",
    srcs = ["Tests/LibTwoTests.swift"],
    minimum_os_version = "15.0",
    deps = [
        ":LibTwo",
    ],
    visibility = ["@rules_xcodeproj//xcodeproj:generated"],
)

swift_library(
    name = "External",
    srcs = ["External/External.swift"],
    module_name = "External",
)

With the following rules_xcodeproj scheme:

xcschemes.scheme(
    name = "LibTwo_Scheme",
    run = xcschemes.run(
        build_targets = [
            "//LibTwo",
        ],
    ),
    test = xcschemes.test(
        build_targets = [
            "//LibTwo",
        ],
        test_targets = [
            "//LibTwo:LibTwoTests",
        ],
    ),
),

When generating the project the LibTwo_Scheme's LibTwo target does not merge and we end up with a scheme that looks like:

With LibTwo making up two targets: LibTwo (Static Framework) and LibTwo (Library). I would expect these to be merged into a single LibTwo target in Xcode as is the case when using apple_framework as deps.

I tested both 2.7.0 and 2.5.2 and both seem to have the same issue.
I added a reproducing example in: #3093

Reproduction steps

1. Checkout Add rules_ios example depending on swift_library #3093

2. cd examples/rules_ios

3. bazel run //:xcodeproj-incremental

4. xed rules_ios.xcodeproj

5. Select the LibTwo_Scheme target

6. Attempt to build the target

7. Observe the failure:

   /path/_CompileStub_.m Build input file cannot be found: '/path/_CompileStub_.m'.
   Did you forget to declare this file as an output of a script phase or custom build rule which produces it?
   

Expected behavior

The LibTwo target is merged into a single target so that building it succeeds.

rules_xcodeproj version

2.7.0

Xcode version

15.4

Bazel version

7.2.0

rules_apple version

3.9.2

rules_swift version

2.1.1

Additional information

No response

[luispadron]

As a workaround (and potentially helps narrow down the issue): manually changing the target in the scheme from LibTwo (Static Framework) to LibTwo (Library) fixes the build.

[luispadron]

If I remove use of transitive_deps from the merging logic then target merging works as expected and the build also passes.

However, indexing seems to fail when making changes:

examples/rules_ios/LibTwo/Sources/LibTwo.swift:1:8 No such module 'External'

[luispadron]

As a workaround we have this rules_ios specific patch right now, working on generalizing it so we can upstream:

diff --git xcodeproj/internal/processed_targets/mergeable_infos.bzl xcodeproj/internal/processed_targets/mergeable_infos.bzl
index f04ccb0c..e98c8b55 100644
--- xcodeproj/internal/processed_targets/mergeable_infos.bzl
+++ xcodeproj/internal/processed_targets/mergeable_infos.bzl
@@ -112,6 +112,32 @@ def _calculate_mergeable_info(
             swift = swift,
         )
 
+    if len(mergeable_infos) > 2:
+        rules_ios_swift_library_info = [info for info in mergeable_infos if info.id and info.id.split(" ")[0].endswith("_swift")]
+        rules_ios_objc_library_info = [info for info in mergeable_infos if info.id and info.id.split(" ")[0].endswith("_objc")]
+        swift = None
+        cc = None
+        if len(rules_ios_swift_library_info) == 1:
+            swift = rules_ios_swift_library_info[0]
+        if len(rules_ios_objc_library_info) == 1:
+            cc = rules_ios_objc_library_info[0]
+
+        if cc and swift:
+            return _handle_mixed_language_mergeable_infos(
+                cc = cc,
+                dynamic_frameworks = dynamic_frameworks,
+                product_type = product_type,
+                swift = swift,
+            )
+        elif cc:
+            return _cc_mergeable_info(mergeable_info = cc)
+        elif swift:
+            return _swift_mergeable_info(
+                dynamic_frameworks = dynamic_frameworks,
+                mergeable_info = swift,
+                product_type = product_type,
+            )
+
     # Unmergeable source target count
     return None