Roll forward of commit deeeb31f8ba0f196fbc9ca2a177d59d57ea50b32.

* Fixed breakage in shell tools with an old bazel binary.

Rollback of commit deeeb31f8ba0f196fbc9ca2a177d59d57ea50b32.

*** Reason for rollback ***

Breaks builds with current blaze

*** Original change description ***

Add a way to select non-default Xcode toolchain

* Adds a flag --xcode_toolchain which sets TOOLCHAINS env variable for xcrun.
* Updates swift_library to work with this flag when selecting Swift runtime
location.
* By default the flag has a null value and is not set in env.

--
MOS_MIGRATED_REVID=135238820

4 files changed, 70 insertions, 17 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/apple/AppleCommandLineOptions.java b/src/main/java/com/google/devtools/build/lib/rules/apple/AppleCommandLineOptions.java
index 5d2830a049..3d71ca5ad8 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/apple/AppleCommandLineOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/apple/AppleCommandLineOptions.java
@@ -227,6 +227,17 @@ public class AppleCommandLineOptions extends FragmentOptions {
     }
   }
 
+  @Option(
+    name = "xcode_toolchain",
+    defaultValue = "null",
+    category = "flags",
+    help = "The identifier of an Xcode toolchain to use for builds. Currently only the toolchains "
+           + "that ship with Xcode are supported. For example, in addition to the default toolchain"
+           + " Xcode 8 has 'com.apple.dt.toolchain.Swift_2_3' which can be used for building legacy"
+           + " Swift code."
+  )
+  public String xcodeToolchain;
+
   @Option(name = "apple_bitcode",
       converter = AppleBitcodeMode.Converter.class,
       // TODO(blaze-team): Default to embedded_markers when fully implemented.
diff --git a/src/main/java/com/google/devtools/build/lib/rules/apple/AppleConfiguration.java b/src/main/java/com/google/devtools/build/lib/rules/apple/AppleConfiguration.java
index 59a6fc1403..e0d242703f 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/apple/AppleConfiguration.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/apple/AppleConfiguration.java
@@ -84,6 +84,7 @@ public class AppleConfiguration extends BuildConfiguration.Fragment {
   private final ImmutableList<String> tvosCpus;
   private final AppleBitcodeMode bitcodeMode;
   private final Label xcodeConfigLabel;
+  @Nullable private final String xcodeToolchain;
   @Nullable private final Label defaultProvisioningProfileLabel;
   private final boolean disableNativeSwiftRules;
 
@@ -127,6 +128,7 @@ public class AppleConfiguration extends BuildConfiguration.Fragment {
     this.xcodeConfigLabel =
         Preconditions.checkNotNull(appleOptions.xcodeVersionConfig, "xcodeConfigLabel");
     this.defaultProvisioningProfileLabel = appleOptions.defaultProvisioningProfile;
+    this.xcodeToolchain = appleOptions.xcodeToolchain;
     this.disableNativeSwiftRules = appleOptions.disableNativeSwiftRules;
   }
 
@@ -519,6 +521,17 @@ public class AppleConfiguration extends BuildConfiguration.Fragment {
     return Joiner.on('-').join(components);
   }
 
+  /** Returns the identifier for an Xcode toolchain to use with tools. */
+  @SkylarkCallable(
+    name = "xcode_toolchain",
+    doc = "Identifier for the custom Xcode toolchain to use in build or None if not specified",
+    allowReturnNones = true,
+    structField = true
+  )
+  public String getXcodeToolchain() {
+    return xcodeToolchain;
+  }
+
   /**
    * Whether the native Swift support should be disabled. Used to deprecate said functionality.
    */
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java b/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java
index fa16aaf3f9..8136e837ca 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java
@@ -1445,9 +1445,22 @@ public final class CompilationSupport {
     }
 
     if (objcProvider.is(USES_SWIFT)) {
-      commandLine
-          .add("-L")
-          .add(AppleToolchain.swiftLibDir(appleConfiguration.getSingleArchPlatform()));
+      // Check if there's a swift library path already. If that's not the case - fall back to
+      // the default one. This is for backwards compatibility with Swift native rules.
+      // TODO(b/30281236): Remove when native Swift is deprecated.
+      boolean swiftLibDirSet = false;
+      for (String arg : objcProvider.get(ObjcProvider.LINKOPT)) {
+        if (arg.startsWith("-L") && arg.contains("usr/lib/swift")) {
+          swiftLibDirSet = true;
+          break;
+        }
+      }
+
+      if (!swiftLibDirSet) {
+        commandLine
+            .add("-L")
+            .add(AppleToolchain.swiftLibDir(appleConfiguration.getSingleArchPlatform()));
+      }
     }
 
     for (String linkopt : attributes.linkopts()) {
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/ReleaseBundlingSupport.java b/src/main/java/com/google/devtools/build/lib/rules/objc/ReleaseBundlingSupport.java
index 009b3fddfe..4cf8e6264f 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/ReleaseBundlingSupport.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/ReleaseBundlingSupport.java
@@ -1058,13 +1058,21 @@ public final class ReleaseBundlingSupport {
       return;
     }
 
-    CustomCommandLine.Builder commandLine =
-        CustomCommandLine.builder()
-            .addPath(intermediateArtifacts.swiftFrameworksFileZip().getExecPath())
-            .add("Frameworks")
-            .add("--platform")
-            .add(platform.getLowerCaseNameInPlist())
-            .addExecPath("--scan-executable", combinedArchBinary);
+    AppleConfiguration appleConfiguration = ruleContext.getFragment(AppleConfiguration.class);
+
+    CustomCommandLine.Builder commandLine = CustomCommandLine.builder();
+    if (appleConfiguration.getXcodeToolchain() != null) {
+      commandLine.add("--toolchain").add(appleConfiguration.getXcodeToolchain());
+    }
+
+    commandLine
+        .add("--output_zip_path")
+        .addPath(intermediateArtifacts.swiftFrameworksFileZip().getExecPath())
+        .add("--bundle_path")
+        .add("Frameworks")
+        .add("--platform")
+        .add(platform.getLowerCaseNameInPlist())
+        .addExecPath("--scan-executable", combinedArchBinary);
 
     ruleContext.registerAction(
         ObjcRuleClasses.spawnAppleEnvActionBuilder(ruleContext, platform)
@@ -1082,13 +1090,21 @@ public final class ReleaseBundlingSupport {
       return;
     }
 
-    CustomCommandLine.Builder commandLine =
-        CustomCommandLine.builder()
-            .addPath(intermediateArtifacts.swiftSupportZip().getExecPath())
-            .add("SwiftSupport/" + platform.getLowerCaseNameInPlist())
-            .add("--platform")
-            .add(platform.getLowerCaseNameInPlist())
-            .addExecPath("--scan-executable", combinedArchBinary);
+    AppleConfiguration configuration = ruleContext.getFragment(AppleConfiguration.class);
+
+    CustomCommandLine.Builder commandLine = CustomCommandLine.builder();
+    if (configuration.getXcodeToolchain() != null) {
+      commandLine.add("--toolchain").add(configuration.getXcodeToolchain());
+    }
+
+    commandLine
+        .add("--output_zip_path")
+        .addPath(intermediateArtifacts.swiftSupportZip().getExecPath())
+        .add("--bundle_path")
+        .add("SwiftSupport/" + platform.getLowerCaseNameInPlist())
+        .add("--platform")
+        .add(platform.getLowerCaseNameInPlist())
+        .addExecPath("--scan-executable", combinedArchBinary);
 
     ruleContext.registerAction(
         ObjcRuleClasses.spawnAppleEnvActionBuilder(ruleContext, platform)