Add features support

swiftpkg/internal/pkginfos.bzl

@@ -1437,24 +1437,29 @@ def _new_swift_settings(build_settings):
     defines = []
     unsafe_flags = []
     experimental_features = []
+    upcoming_features = []
     for bs in build_settings:
         if bs.kind == build_setting_kinds.define:
             defines.append(bs)
         elif bs.kind == build_setting_kinds.unsafe_flags:
             unsafe_flags.append(bs)
         elif bs.kind == build_setting_kinds.experimental_features:
             experimental_features.append(bs)
+        elif bs.kind == build_setting_kinds.upcoming_features:
+            upcoming_features.append(bs)
         else:
             # We do not recognize the setting.
             pass
     if len(defines) == 0 and \
        len(unsafe_flags) == 0 and \
-       len(experimental_features) == 0:
+       len(experimental_features) == 0 and \
+       len(upcoming_features) == 0:
         return None
     return struct(
         defines = defines,
         unsafe_flags = unsafe_flags,
         experimental_features = experimental_features,
+        upcoming_features = upcoming_features,
     )
 
 def _new_linker_settings(build_settings):
@@ -1640,6 +1645,7 @@ build_setting_kinds = struct(
     linked_library = "linkedLibrary",
     unsafe_flags = "unsafeFlags",
     experimental_features = "enableExperimentalFeature",
+    upcoming_features = "enableUpcomingFeature",
 )
 
 # MARK: - API Definition

swiftpkg/internal/swiftpkg_build_files.bzl

@@ -114,9 +114,10 @@ def _swift_target_build_file(pkg_ctx, target):
 
     # Check if any of the sources indicate that the module will be used by
     # Objective-C code. If so, generate the bridge header file.
+    features = []
     if target.swift_src_info.has_objc_directive and is_library_target:
         attrs["generates_header"] = True
-        attrs["features"] = ["swift.propagate_generated_module_map"]
+        features.append("swift.propagate_generated_module_map")
 
     if target.swift_settings != None:
         if len(target.swift_settings.defines) > 0:
@@ -134,8 +135,15 @@ def _swift_target_build_file(pkg_ctx, target):
             ]))
         if len(target.swift_settings.experimental_features) > 0:
             for bs in target.swift_settings.experimental_features:
-                copts.append("-enable-experimental-feature")
-                copts.extend(lists.flatten(bzl_selects.new_from_build_setting(bs)))
+                for experimental_feature in lists.flatten(bzl_selects.new_from_build_setting(bs)):
+                    features.append("swift.experimental_feature." + experimental_feature)
+        if len(target.swift_settings.upcoming_features) > 0:
+            for bs in target.swift_settings.upcoming_features:
+                for upcoming_feature in lists.flatten(bzl_selects.new_from_build_setting(bs)):
+                    features.append("swift.upcoming_feature." + upcoming_feature)
+
+    if len(features) > 0:
+        attrs["features"] = features
 
     if len(copts) > 0:
         attrs["copts"] = bzl_selects.to_starlark(copts, mutually_inclusive = True)