SpawnAction.setShellCommand: expect shell path

    SpawnAction.setShellCommand(String) now expects
    the shell interpreter's path as an argument. This
    change enables two things:
    - rules can report an error if the shell is
      missing
    - SpawnAction no longer has to know about a
      default shell

    The new ShToolchain class will later also be
    responsible for retrieving the active shell
    toolchain (added in bazelbuild/bazel@81ed3ad).

    This change brings Bazel closer to not depend on
    the shell unless it has to (e.g. to run shell
    scripts).

    See bazelbuild/bazel#4319

    RELNOTES: none
    PiperOrigin-RevId: 193885943

dataset/GitHub_Java/bazelbuild.bazel/src/main/java/com/google/devtools/build/lib/analysis/CommandHelper.java

@@ -34,6 +34,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Map.Entry;
 import javax.annotation.Nullable;
 
 /**
@@ -129,7 +130,7 @@ public CommandHelper(
     this.toolsRunfilesSuppliers = SkylarkList.createImmutable(toolsRunfilesBuilder.build());
     ImmutableMap.Builder<Label, ImmutableCollection<Artifact>> labelMapBuilder =
         ImmutableMap.builder();
-    for (Map.Entry<Label, Collection<Artifact>> entry : tempLabelMap.entrySet()) {
+    for (Entry<Label, Collection<Artifact>> entry : tempLabelMap.entrySet()) {
       labelMapBuilder.put(entry.getKey(), ImmutableList.copyOf(entry.getValue()));
     }
     this.labelMap = labelMapBuilder.build();

dataset/GitHub_Java/bazelbuild.bazel/src/main/java/com/google/devtools/build/lib/analysis/ShToolchain.java

@@ -0,0 +1,62 @@
+// Copyright 2018 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.
+
+package com.google.devtools.build.lib.analysis;
+
+import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
+import com.google.devtools.build.lib.vfs.PathFragment;
+
+/** Class to work with the shell toolchain, e.g. get the shell interpreter's path. */
+public final class ShToolchain {
+
+  /**
+   * Returns the shell executable's path, or an empty path if not set.
+   *
+   * <p>This method checks the configuration's {@link ShellConfiguration} fragment.
+   */
+  public static PathFragment getPath(BuildConfiguration config) {
+    PathFragment result = PathFragment.EMPTY_FRAGMENT;
+
+    ShellConfiguration configFragment =
+        (ShellConfiguration) config.getFragment(ShellConfiguration.class);
+    if (configFragment != null) {
+      PathFragment path = configFragment.getShellExecutable();
+      if (path != null) {
+        result = path;
+      }
+    }
+
+    return result;
+  }
+
+  /**
+   * Returns the shell executable's path, or reports a rule error if the path is empty.
+   *
+   * <p>This method checks the rule's configuration's {@link ShellConfiguration} fragment for the
+   * shell executable's path. If null or empty, the method reports an error against the rule.
+   */
+  public static PathFragment getPathOrError(RuleContext ctx) {
+    PathFragment result = getPath(ctx.getConfiguration());
+
+    if (result.isEmpty()) {
+      ctx.ruleError(
+          "This rule needs a shell interpreter. Use the --shell_executable=<path> flag to specify"
+              + " the interpreter's path, e.g. --shell_executable=/usr/local/bin/bash");
+    }
+
+    return result;
+  }
+
+  private ShToolchain() {}
+}