Include the headers from direct dependencies of a Swift target when compiling the explicit module for its generated header.

PiperOrigin-RevId: 372240650

Author: allevato

swift/internal/compiling.bzl

@@ -66,6 +66,7 @@ load(
     ":utils.bzl",
     "collect_cc_libraries",
     "compact",
+    "compilation_context_for_explicit_module_compilation",
     "get_providers",
     "struct_fields",
 )
@@ -1494,12 +1495,18 @@ def compile(
         feature_configuration = feature_configuration,
         feature_name = SWIFT_FEATURE_NO_GENERATED_MODULE_MAP,
     ):
+        compilation_context_to_compile = (
+            compilation_context_for_explicit_module_compilation(
+                compilation_contexts = [cc_common.create_compilation_context(
+                    headers = depset([compile_outputs.generated_header_file]),
+                )],
+                deps = deps,
+            )
+        )
         precompiled_module = _precompile_clang_module(
             actions = actions,
             bin_dir = bin_dir,
-            cc_compilation_context = cc_common.create_compilation_context(
-                headers = depset([compile_outputs.generated_header_file]),
-            ),
+            cc_compilation_context = compilation_context_to_compile,
             feature_configuration = feature_configuration,
             genfiles_dir = genfiles_dir,
             is_swift_generated_header = True,

swift/internal/swift_clang_module_aspect.bzl

@@ -33,7 +33,11 @@ load(
     "create_module",
     "create_swift_info",
 )
-load(":utils.bzl", "get_providers")
+load(
+    ":utils.bzl",
+    "compilation_context_for_explicit_module_compilation",
+    "get_providers",
+)
 
 _MULTIPLE_TARGET_ASPECT_ATTRS = [
     "deps",
@@ -456,34 +460,12 @@ def _handle_module(
     # a framework import rule. For now, we won't support compiling those as
     # explicit modules; fix this.
     if module_name:
-        # We only need to propagate the information from the compilation
-        # contexts, but we can't merge those directly; we can only merge
-        # `CcInfo` objects. So we "unwrap" the compilation context from each
-        # provider and then "rewrap" it in a new provider that lacks the linking
-        # context so that our merge operation does less work.
-        target_and_deps_cc_infos = [
-            CcInfo(compilation_context = compilation_context),
-        ]
-        for dep in getattr(attr, "deps", []):
-            if CcInfo in dep:
-                target_and_deps_cc_infos.append(
-                    CcInfo(
-                        compilation_context = dep[CcInfo].compilation_context,
-                    ),
-                )
-            if apple_common.Objc in dep:
-                target_and_deps_cc_infos.append(
-                    CcInfo(
-                        compilation_context = cc_common.create_compilation_context(
-                            includes = dep[apple_common.Objc].strict_include,
-                        ),
-                    ),
-                )
-
-        compilation_context_to_compile = cc_common.merge_cc_infos(
-            direct_cc_infos = target_and_deps_cc_infos,
-        ).compilation_context
-
+        compilation_context_to_compile = (
+            compilation_context_for_explicit_module_compilation(
+                compilation_contexts = [compilation_context],
+                deps = getattr(attr, "deps", []),
+            )
+        )
         precompiled_module = precompile_clang_module(
             actions = aspect_ctx.actions,
             bin_dir = aspect_ctx.bin_dir,

swift/internal/utils.bzl

@@ -168,6 +168,51 @@ def create_cc_info(
         direct_cc_infos = local_cc_infos,
     )
 
+def compilation_context_for_explicit_module_compilation(
+        compilation_contexts,
+        deps):
+    """Returns a compilation context suitable for compiling an explicit module.
+
+    Args:
+        compilation_contexts: `CcCompilationContext`s that provide information
+            about headers and include paths for the target being compiled.
+        deps: Direct dependencies of the target being compiled.
+
+    Returns:
+        A `CcCompilationContext` containing information needed when compiling an
+        explicit module, such as the headers and search paths of direct
+        dependencies (since Clang needs to find those on the file system in
+        order to map them to a module).
+    """
+    cc_infos = [
+        CcInfo(compilation_context = compilation_context)
+        for compilation_context in compilation_contexts
+    ]
+
+    for dep in deps:
+        if CcInfo in dep:
+            # TODO(b/179692096): We only need to propagate the information from
+            # the compilation contexts, but we can't merge those directly; we
+            # can only merge `CcInfo` objects. So we "unwrap" the compilation
+            # context from each provider and then "rewrap" it in a new provider
+            # that lacks the linking context so that our merge operation does
+            # less work.
+            cc_infos.append(
+                CcInfo(compilation_context = dep[CcInfo].compilation_context),
+            )
+        if apple_common.Objc in dep:
+            cc_infos.append(
+                CcInfo(
+                    compilation_context = cc_common.create_compilation_context(
+                        includes = dep[apple_common.Objc].strict_include,
+                    ),
+                ),
+            )
+
+    return cc_common.merge_cc_infos(
+        direct_cc_infos = cc_infos,
+    ).compilation_context
+
 def expand_locations(ctx, values, targets = []):
     """Expands the `$(location)` placeholders in each of the given values.