feat: support storing Swift dependency files in a sub-package

.bazelrc

@@ -1,7 +1,7 @@
 # To update these lines, execute 
 # `bazel run @contrib_rules_bazel_integration_test//tools:update_deleted_packages`
-build --deleted_packages=examples/http_archive_ext_deps,examples/http_archive_ext_deps/Sources/MyDequeModule,examples/http_archive_ext_deps/Sources/PrintStuff,examples/http_archive_ext_deps/Tests/MyDequeModuleTests,examples/http_archive_ext_deps/third_party,examples/interesting_deps,examples/ios_sim,examples/ios_sim/Sources/Foo,examples/ios_sim/Tests/FooTests,examples/objc_code,examples/pkg_manifest_minimal,examples/pkg_manifest_minimal/Sources/MyExecutable,examples/pkg_manifest_minimal/Sources/MyLibrary,examples/pkg_manifest_minimal/Tests/MyLibraryTests,examples/pkg_manifest_minimal/third_party,examples/vapor_example,examples/vapor_example/Sources/App,examples/vapor_example/Sources/Run,examples/vapor_example/Tests/AppTests,examples/xcmetrics_example
-query --deleted_packages=examples/http_archive_ext_deps,examples/http_archive_ext_deps/Sources/MyDequeModule,examples/http_archive_ext_deps/Sources/PrintStuff,examples/http_archive_ext_deps/Tests/MyDequeModuleTests,examples/http_archive_ext_deps/third_party,examples/interesting_deps,examples/ios_sim,examples/ios_sim/Sources/Foo,examples/ios_sim/Tests/FooTests,examples/objc_code,examples/pkg_manifest_minimal,examples/pkg_manifest_minimal/Sources/MyExecutable,examples/pkg_manifest_minimal/Sources/MyLibrary,examples/pkg_manifest_minimal/Tests/MyLibraryTests,examples/pkg_manifest_minimal/third_party,examples/vapor_example,examples/vapor_example/Sources/App,examples/vapor_example/Sources/Run,examples/vapor_example/Tests/AppTests,examples/xcmetrics_example
+build --deleted_packages=examples/http_archive_ext_deps,examples/http_archive_ext_deps/Sources/MyDequeModule,examples/http_archive_ext_deps/Sources/PrintStuff,examples/http_archive_ext_deps/Tests/MyDequeModuleTests,examples/http_archive_ext_deps/third_party,examples/interesting_deps,examples/ios_sim,examples/ios_sim/Sources/Foo,examples/ios_sim/Tests/FooTests,examples/objc_code,examples/pkg_manifest_minimal,examples/pkg_manifest_minimal/Sources/MyExecutable,examples/pkg_manifest_minimal/Sources/MyLibrary,examples/pkg_manifest_minimal/Tests/MyLibraryTests,examples/pkg_manifest_minimal/third_party,examples/vapor_example,examples/vapor_example/Sources/App,examples/vapor_example/Sources/Run,examples/vapor_example/Tests/AppTests,examples/vapor_example/swift,examples/xcmetrics_example
+query --deleted_packages=examples/http_archive_ext_deps,examples/http_archive_ext_deps/Sources/MyDequeModule,examples/http_archive_ext_deps/Sources/PrintStuff,examples/http_archive_ext_deps/Tests/MyDequeModuleTests,examples/http_archive_ext_deps/third_party,examples/interesting_deps,examples/ios_sim,examples/ios_sim/Sources/Foo,examples/ios_sim/Tests/FooTests,examples/objc_code,examples/pkg_manifest_minimal,examples/pkg_manifest_minimal/Sources/MyExecutable,examples/pkg_manifest_minimal/Sources/MyLibrary,examples/pkg_manifest_minimal/Tests/MyLibraryTests,examples/pkg_manifest_minimal/third_party,examples/vapor_example,examples/vapor_example/Sources/App,examples/vapor_example/Sources/Run,examples/vapor_example/Tests/AppTests,examples/vapor_example/swift,examples/xcmetrics_example
 
 # Import Shared settings
 import %workspace%/shared.bazelrc

docs/faq.md

@@ -12,6 +12,7 @@
 * [Can I just manage my external Swift packages and not generate Bazel build files for my project?](#can-i-just-manage-my-external-swift-packages-and-not-generate-bazel-build-files-for-my-project)
 * [After running //:swift\_update\_pkgs , I see a \.build directory\. What is it? Do I need it?](#after-running-swift_update_pkgs-i-see-a-build-directory-what-is-it-do-i-need-it)
 * [Does the Gazelle plugin run Swift package manager with every execution?](#does-the-gazelle-plugin-run-swift-package-manager-with-every-execution)
+* [Can I store the Swift dependency files in a sub\-package (i\.e\., not in the root of the workspace)?](#can-i-store-the-swift-dependency-files-in-a-sub-package-ie-not-in-the-root-of-the-workspace)
 <!-- MARKDOWN TOC: END -->
 
 ## Why use Gazelle and Go?
@@ -83,9 +84,15 @@ update the version selection for a dependency). The `update` mode for the Gazell
 Bazel build files for your project. It uses information written to the `swift_deps_index.json` and
 the source files that exist in your project to generate the Bazel build files.
 
+## Can I store the Swift dependency files in a sub-package (i.e., not in the root of the workspace)?
+
+Yes. The [vapor example] demonstrates storing the Swift dependency files in a sub-package called
+`swift`.
+
 
 [loading phase]: https://bazel.build/run/build#loading 
 [quickstart]: https://github.com/cgrindel/swift_bazel/blob/main/README.md#quickstart
 [rules_spm]: https://github.com/cgrindel/rules_spm/
 [rules_swift]: https://github.com/bazelbuild/rules_swift
 [Gazelle framework]: https://github.com/bazelbuild/bazel-gazelle/blob/master/extend.md
+[vapor example]: /examples/vapor_example

examples/vapor_example/BUILD.bazel

@@ -1,46 +1,33 @@
 load("@bazel_gazelle//:def.bzl", "gazelle", "gazelle_binary")
-load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
 load("@cgrindel_bazel_starlib//bzltidy:defs.bzl", "tidy")
-load("@cgrindel_swift_bazel//swiftpkg:defs.bzl", "swift_update_packages")
 
 tidy(
     name = "tidy",
     targets = [
-        ":swift_update_pkgs",
+        "//swift:update_pkgs",
         ":update_build_files",
     ],
 )
 
 # MARK: - Gazelle
 
-# Ignore the Swift build folder
-# gazelle:exclude .build
-
 gazelle_binary(
     name = "gazelle_bin",
     languages = [
         "@bazel_skylib//gazelle/bzl",
         "@cgrindel_swift_bazel//gazelle",
     ],
+    visibility = ["//:__subpackages__"],
 )
 
 gazelle(
     name = "update_build_files",
+    args = [
+        "-swift_dependency_index=swift/deps_index.json",
+    ],
     gazelle = ":gazelle_bin",
 )
 
-swift_update_packages(
-    name = "swift_update_pkgs",
-    gazelle = ":gazelle_bin",
-)
-
-bzl_library(
-    name = "swift_deps",
-    srcs = ["swift_deps.bzl"],
-    visibility = ["//visibility:public"],
-    deps = ["@cgrindel_swift_bazel//swiftpkg:defs"],
-)
-
 # Vapor was not happy building under 13.2.1. Fix the version for now.
 # See Keith's article for more details:
 # https://www.smileykeith.com/2021/03/08/locking-xcode-in-bazel/

examples/vapor_example/README.md

@@ -6,6 +6,8 @@ Swift and Clang dependencies. Some of their Clang modules
 have custom module maps. This example exercises the `swift_bazel` code that processes custom module
 maps and handles novel Clang module linking issues.
 
+Also, this example demonstrates how to store the Swift-specific dependency files in a sub-package.
+
 
 ## Linux Prequisites
 

examples/vapor_example/WORKSPACE

@@ -44,9 +44,9 @@ load(
     "@build_bazel_rules_swift//swift:repositories.bzl",
     "swift_rules_dependencies",
 )
-load("//:swift_deps.bzl", "swift_dependencies")
+load("//swift:deps.bzl", "swift_dependencies")
 
-# gazelle:repository_macro swift_deps.bzl%swift_dependencies
+# gazelle:repository_macro swift/deps.bzl%swift_dependencies
 swift_dependencies()
 
 swift_rules_dependencies()

examples/vapor_example/set_up_clean_test

@@ -11,10 +11,10 @@ find "${script_dir}" \
   -exec rm {} \;
 
 # Remove the SPM build folder
-rm -rf .build
+rm -rf "${script_dir}/swift/.build"
 
-# Replace the swift_deps.bzl with no declarations.
-cat > "${script_dir}/swift_deps.bzl"  <<-EOF
+# Replace the swift/deps.bzl with no declarations.
+cat > "${script_dir}/swift/deps.bzl"  <<-EOF
 def swift_dependencies():
     pass
 EOF
@@ -29,37 +29,50 @@ load("@cgrindel_swift_bazel//swiftpkg:defs.bzl", "swift_update_packages")
 tidy(
     name = "tidy",
     targets = [
-        ":swift_update_pkgs",
+        "//swift:update_pkgs",
         ":update_build_files",
     ],
 )
 
 # MARK: - Gazelle
 
-# Ignore the Swift build folder
-# gazelle:exclude .build
-
 gazelle_binary(
     name = "gazelle_bin",
     languages = [
         "@bazel_skylib//gazelle/bzl",
         "@cgrindel_swift_bazel//gazelle",
     ],
+    visibility = ["//:__subpackages__"],
 )
 
 gazelle(
     name = "update_build_files",
+    args = [
+        "-swift_dependency_index=swift/deps_index.json",
+    ],
     gazelle = ":gazelle_bin",
 )
 
+EOF
+
+cat > "${script_dir}/swift/BUILD.bazel"  <<-EOF
+load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
+load("@cgrindel_swift_bazel//swiftpkg:defs.bzl", "swift_update_packages")
+
+# Ignore the Swift build folder
+# gazelle:exclude .build
+
 swift_update_packages(
-    name = "swift_update_pkgs",
-    gazelle = ":gazelle_bin",
+    name = "update_pkgs",
+    gazelle = "//:gazelle_bin",
+    package_manifest = "swift/Package.swift",
+    swift_deps = "swift/deps.bzl",
+    swift_deps_index = "swift/deps_index.json",
 )
 
 bzl_library(
-    name = "swift_deps",
-    srcs = ["swift_deps.bzl"],
+    name = "deps",
+    srcs = ["deps.bzl"],
     visibility = ["//visibility:public"],
     deps = ["@cgrindel_swift_bazel//swiftpkg:defs"],
 )

examples/vapor_example/swift/BUILD.bazel

@@ -0,0 +1,25 @@
+load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
+load("@cgrindel_swift_bazel//swiftpkg:defs.bzl", "swift_update_packages")
+
+# NOTE: If you decide to move the Swift dependency files like this example, do
+# not forget to update the `gazelle` declaration `//:update_build_files` to
+# point at the new location of the Swift dependency index JSON file.  Also, the
+# `//:gazelle_bin target` must be visible to this package.
+
+# Ignore the Swift build folder
+# gazelle:exclude .build
+
+swift_update_packages(
+    name = "update_pkgs",
+    gazelle = "//:gazelle_bin",
+    package_manifest = "swift/Package.swift",
+    swift_deps = "swift/deps.bzl",
+    swift_deps_index = "swift/deps_index.json",
+)
+
+bzl_library(
+    name = "deps",
+    srcs = ["deps.bzl"],
+    visibility = ["//visibility:public"],
+    deps = ["@cgrindel_swift_bazel//swiftpkg:defs"],
+)