[iOS/Mac/GN] The framework_bundle template should not force dependencies to link it.

build/config/mac/rules.gni

Index: build/config/mac/rules.gni
diff --git a/build/config/mac/rules.gni b/build/config/mac/rules.gni
index 11b86c9d6f88f33c8f727afd56a58952ff667e03..9d624a7bac72f4a7744ba5b275492fe10a3d21e3 100644
--- a/build/config/mac/rules.gni
+++ b/build/config/mac/rules.gni
@@ -7,6 +7,12 @@ import("//build/config/mac/mac_sdk.gni")
 
 # This is used as the base template for both iOS and Mac frameworks..
 #
+# By default, the bundle target this template generates does not link the
+# resulting framework into anything that depends on it. If a dependency wants
+# a link-time (as well as build-time) dependency on the framework bundle,
+# depend against "$target_name+link". If only the build-time dependency is
+# required (e.g., for copying into another bundle), then use "$target_name".
+#
 # Arguments
 #
 #     output_name:
@@ -19,6 +25,70 @@ import("//build/config/mac/mac_sdk.gni")
 #         structure will not be created, and build output will go directly
 #         into the framework subdirectory.
 #
+# This template provides two targets for the resulting framework bundle. The
+# link-time behavior varies depending on which of the two targets below is
+# added as a dependency:
+#   - $target_name only adds a build-time dependency. Targets that depend on
+#     it will not link against the framework.
+#   - $target_name+link adds a build-time and link-time dependency. Targets
+#     that depend on it will link against the framework.
+#
+# The build-time-only dependency is used for when a target needs to use the
+# framework either only for resources, or because the target loads it at run-
+# time, via dlopen() or NSBundle. The link-time dependency will cause the
+# dependee to have the framework loaded by dyld at launch.
+#
+# Example of build-time only dependency:
+#
+#     framework_bundle("CoreTeleportation") {
+#       sources = [ ... ]
+#     }
+#
+#     bundle_data("core_teleportation_bundle_data") {
+#       deps = [ ":CoreTeleportation" ]
+#       sources = [ "$root_out_dir/CoreTeleportation.framework" ]
+#       outputs = [ "{{bundle_root_dir}}/Frameworks/{{source_file_part}}" ]
+#     }
+#
+#     app_bundle("GoatTeleporter") {
+#       sources = [ ... ]
+#       deps = [
+#         ":core_teleportation_bundle_data",
+#       ]
+#     }
+#
+# The GoatTeleporter.app will not directly link against
+# CoreTeleportation.framework, but it will be included in the bundle's
+# Frameworks directory.
+#
+# Example of link-time dependency:
+#
+#     framework_bundle("CoreTeleportation") {
+#       sources = [ ... ]
+#       ldflags = [
+#         "-install_name",
+#         "@executable_path/../Frameworks/$target_name.framework"
+#       ]
+#     }
+#
+#     bundle_data("core_teleportation_bundle_data") {
+#       deps = [ ":CoreTeleportation+link" ]
+#       sources = [ "$root_out_dir/CoreTeleportation.framework" ]
+#       outputs = [ "{{bundle_root_dir}}/Frameworks/{{source_file_part}}" ]
+#     }
+#
+#     app_bundle("GoatTeleporter") {
+#       sources = [ ... ]
+#       deps = [
+#         ":core_teleportation_bundle_data",
+#       ]
+#     }
+#
+# Note that the framework is still copied to the app's bundle, but dyld will
+# load this library when the app is launched because it uses the "+link"
+# target as a dependency. This also requires that the framework set its
+# install_name so that dyld can locate it.
+#
 # See "gn help shared_library" for more information on arguments supported
 # by shared library target.
 template("framework_bundle") {
@@ -80,10 +150,7 @@ template("framework_bundle") {
     # TODO(sdefresne): should we have a framework_dirs similar to lib_dirs
     # and include_dirs to avoid duplicate values on the command-line.
     visibility = [ ":$_framework_target" ]
-    common_flags = [ "-F" + rebase_path("$root_out_dir/.", root_out_dir) ]
-    cflags_objc = common_flags
-    cflags_objcc = common_flags
-    ldflags = common_flags
+    ldflags = [ "-F" + rebase_path("$root_out_dir/.", root_out_dir) ]
     lib_dirs = [ root_out_dir ]
     libs = [ _framework_name ]
   }
@@ -100,7 +167,10 @@ template("framework_bundle") {
     if (defined(_framework_version)) {
       visibility = [ ":$_target_name" ]
     } else {
-      forward_variables_from(invoker, [ "visibility" ])
+      if (defined(invoker.visibility)) {
+        visibility = invoker.visibility
+        visibility += [ ":$_target_name+link" ]
+      }
     }
 
     if (!defined(public_deps)) {
@@ -108,8 +178,6 @@ template("framework_bundle") {
     }
     public_deps += [ ":$_shared_library_bundle_data" ]
 
-    public_configs = [ ":$_framework_public_config" ]
-
     bundle_root_dir = _framework_root_dir
     bundle_resources_dir = "$bundle_root_dir/Resources"
     bundle_executable_dir = "$bundle_root_dir"
@@ -117,11 +185,13 @@ template("framework_bundle") {
 
   if (defined(_framework_version)) {
     action(_target_name) {
-      forward_variables_from(invoker,
-                             [
-                               "visibility",
-                               "testonly",
-                             ])
+      forward_variables_from(invoker, [ "testonly" ])
+
+      if (defined(invoker.visibility)) {
+        visibility = invoker.visibility
+        visibility += [ ":$_target_name+link" ]
+      }
+
       script = "$root_out_dir/gyp-mac-tool"
       outputs = [
         "$root_out_dir/$_framework_name/Versions/Current",
@@ -136,6 +206,18 @@ template("framework_bundle") {
       ]
     }
   }
+
+  group(_target_name + "+link") {
+    forward_variables_from(invoker,
+                           [
+                             "visibility",
+                             "testonly",
+                           ])
+    public_deps = [
+      ":$_target_name",
+    ]
+    public_configs = [ ":$_framework_public_config" ]
+  }
 }
 
 # Template to combile .xib or .storyboard files.
@@ -228,6 +310,13 @@ template("mac_xib_bundle_data") {
 
 # Template to package a shared library into a Mac framework bundle.
 #
+# This template provides two targets to control whether the framework is
+# merely built when targets depend on it, or whether it is linked as well:
+# "$target_name" and "$target_name+link".
+#
+# See the //build/config/mac/rules.gni:framework_bundle for a discussion
+# and examples.
+#
 # Arguments
 #
 #     info_plist: