Handle swift toolchain and platform placeholds in swift worker.

PiperOrigin-RevId: 462733373

tools/common/BUILD

@@ -56,6 +56,18 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "swift_substitutions",
+    srcs = ["swift_substitutions.cc"],
+    hdrs = ["swift_substitutions.h"],
+    deps = [
+        ":bazel_substitutions",
+        "@com_google_absl//absl/container:flat_hash_map",
+        "@com_google_absl//absl/strings",
+        "@com_google_absl//absl/types:optional",
+    ],
+)
+
 cc_library(
     name = "temp_file",
     hdrs = ["temp_file.h"],

tools/common/swift_substitutions.cc

@@ -0,0 +1,65 @@
+// Copyright 2021 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "tools/common/swift_substitutions.h"
+
+#include "absl/strings/str_replace.h"
+#include "absl/strings/substitute.h"
+#include "absl/types/optional.h"
+
+namespace bazel_rules_swift {
+namespace {
+// Returns the value of the given environment variable, or nullopt if it wasn't
+// set.
+absl::optional<std::string> GetEnvironmentVariable(absl::string_view name) {
+  std::string null_terminated_name(name.data(), name.length());
+  char* env_value = getenv(null_terminated_name.c_str());
+  if (env_value == nullptr) {
+    return absl::nullopt;
+  }
+  return env_value;
+}
+
+}  // namespace
+
+SwiftPlaceholderSubstitutions::SwiftPlaceholderSubstitutions() {
+  if (absl::optional<std::string> swift_toolchain_override =
+          GetEnvironmentVariable("SWIFT_TOOLCHAIN_OVERRIDE");
+      swift_toolchain_override.has_value()) {
+    substitutions_[kSwiftToolchainDir] = *swift_toolchain_override;
+  } else {
+    substitutions_[kSwiftToolchainDir] =
+        "__BAZEL_XCODE_DEVELOPER_DIR__/Toolchains/XcodeDefault.xctoolchain";
+  }
+
+  if (absl::optional<std::string> swift_platform_override =
+          GetEnvironmentVariable("SWIFT_PLATFORM_OVERRIDE");
+      swift_platform_override.has_value()) {
+    substitutions_[kSwiftPlatformDir] = *swift_platform_override;
+  } else if (absl::optional<std::string> apple_sdk_platform =
+                 GetEnvironmentVariable("APPLE_SDK_PLATFORM");
+             apple_sdk_platform.has_value()) {
+    substitutions_[kSwiftPlatformDir] =
+        absl::Substitute("__BAZEL_XCODE_DEVELOPER_DIR__/Platforms/$0.platform",
+                         *apple_sdk_platform);
+  }
+}
+
+bool SwiftPlaceholderSubstitutions::Apply(std::string& arg) {
+  // Order here matters. Swift substitutions must be applied first.
+  // They can produce bazel substitutions that require further substitution.
+  bool swift_changed = absl::StrReplaceAll(substitutions_, &arg) > 0;
+  return bazel_substitutions_.Apply(arg) > 0 || swift_changed;
+}
+}  // namespace bazel_rules_swift

tools/common/swift_substitutions.h

@@ -0,0 +1,50 @@
+// Copyright 2021 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef THIRD_PARTY_BAZEL_RULES_RULES_SWIFT_TOOLS_COMMON_SWIFT_SUBSTITUTIONS_H_
+#define THIRD_PARTY_BAZEL_RULES_RULES_SWIFT_TOOLS_COMMON_SWIFT_SUBSTITUTIONS_H_
+
+#include "absl/container/flat_hash_map.h"
+#include "absl/strings/string_view.h"
+#include "tools/common/bazel_substitutions.h"
+
+namespace bazel_rules_swift {
+
+// Manages the substitution of special Swift placeholder strings in command line
+// arguments that are used to defer the determination of toolchain and platform
+// paths until execution time.
+class SwiftPlaceholderSubstitutions {
+ public:
+  SwiftPlaceholderSubstitutions();
+
+  // Applies any necessary substitutions to `arg` and returns true if this
+  // caused the string to change.
+  bool Apply(std::string &arg);
+
+  inline static constexpr absl::string_view kSwiftToolchainDir =
+      "__SWIFT_TOOLCHAIN_DIR__";
+  inline static constexpr absl::string_view kSwiftPlatformDir =
+      "__SWIFT_PLATFORM_DIR__";
+
+ private:
+  // A mapping from bazel substitutes to their values.
+  BazelPlaceholderSubstitutions bazel_substitutions_;
+
+  // A mapping from swift toolchain to their substituted values.
+  absl::flat_hash_map<std::string, std::string> substitutions_;
+};
+
+}  // namespace bazel_rules_swift
+
+#endif  // THIRD_PARTY_BAZEL_RULES_RULES_SWIFT_TOOLS_COMMON_SWIFT_SUBSTITUTIONS_H_

tools/worker/BUILD

@@ -52,9 +52,9 @@ cc_library(
     srcs = ["swift_runner.cc"],
     hdrs = ["swift_runner.h"],
     deps = [
-        "//tools/common:bazel_substitutions",
         "//tools/common:file_system",
         "//tools/common:process",
+        "//tools/common:swift_substitutions",
         "//tools/common:temp_file",
         "@com_google_absl//absl/strings",
     ],

tools/worker/swift_runner.cc

@@ -19,9 +19,9 @@
 #include "absl/strings/str_cat.h"
 #include "absl/strings/string_view.h"
 #include "absl/strings/strip.h"
-#include "tools/common/bazel_substitutions.h"
 #include "tools/common/file_system.h"
 #include "tools/common/process.h"
+#include "tools/common/swift_substitutions.h"
 #include "tools/common/temp_file.h"
 
 namespace bazel_rules_swift {
@@ -226,7 +226,7 @@ bool SwiftRunner::ProcessArgument(
   // ensure that our defensive quoting kicks in if an argument contains a
   // space, even if no other changes would have been made.
   std::string new_arg(arg);
-  bool changed = bazel_placeholder_substitutions_.Apply(new_arg) ||
+  bool changed = swift_placeholder_substitutions_.Apply(new_arg) ||
                  absl::StrContains(new_arg, ' ');
   consumer(new_arg);
   return changed;

tools/worker/swift_runner.h

@@ -22,7 +22,7 @@
 #include <vector>
 
 #include "absl/strings/string_view.h"
-#include "tools/common/bazel_substitutions.h"
+#include "tools/common/swift_substitutions.h"
 #include "tools/common/temp_file.h"
 
 namespace bazel_rules_swift {
@@ -108,8 +108,8 @@ class SwiftRunner {
 
   // A mapping of Bazel placeholder strings to the actual paths that should be
   // substituted for them. Supports Xcode resolution on Apple OSes.
-  bazel_rules_swift::BazelPlaceholderSubstitutions
-      bazel_placeholder_substitutions_;
+  bazel_rules_swift::SwiftPlaceholderSubstitutions
+      swift_placeholder_substitutions_;
 
   // The arguments, post-substitution, passed to the spawner.
   std::vector<std::string> args_;