Introduce a Skyframe function: ActionEnvironmentFunction

ActionEnvironmentFunction returns the list of environment
variable with the one overwritten by --action_env being
replaced. This let other Skyframe function declares
dependency to any value of the environment and being
influenced by the --action_env flag.

This will be used to declare dependency of remote repositories
on environment variables (step 3 of
https://bazel.build/designs/2016/10/18/repository-invalidation.html)

--
Change-Id: I1ed3fb6f48e8e17d4d64c903fccecb6ed7596350
Reviewed-on: https://cr.bazel.build/7974
PiperOrigin-RevId: 146918603
MOS_MIGRATED_REVID=146918603

1 files changed, 78 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/ActionEnvironmentFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/ActionEnvironmentFunction.java
new file mode 100644
index 0000000000..ea4cde03df
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/ActionEnvironmentFunction.java
@@ -0,0 +1,78 @@
+// Copyright 2017 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.skyframe;
+
+import com.google.common.collect.ImmutableList;
+import com.google.devtools.build.skyframe.SkyFunction;
+import com.google.devtools.build.skyframe.SkyKey;
+import com.google.devtools.build.skyframe.SkyValue;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import javax.annotation.Nullable;
+
+/**
+ * Skyframe function that provides the effective value for a client environment variable. This will
+ * either be the value coming from the default client environment, or the value coming from the
+ * --action_env flag, if the variable's value is explicitly set.
+ */
+public final class ActionEnvironmentFunction implements SkyFunction {
+
+  @Nullable
+  @Override
+  public String extractTag(SkyKey skyKey) {
+    return null;
+  }
+
+  @Nullable
+  @Override
+  public SkyValue compute(SkyKey skyKey, Environment env) throws InterruptedException {
+    Map<String, String> actionEnv = PrecomputedValue.ACTION_ENV.get(env);
+    String key = (String) skyKey.argument();
+    if (actionEnv.containsKey(key) && actionEnv.get(key) != null) {
+      return new ClientEnvironmentValue(actionEnv.get(key));
+    }
+    return env.getValue(SkyKey.create(SkyFunctions.CLIENT_ENVIRONMENT_VARIABLE, key));
+  }
+
+  /** @return the SkyKey to invoke this function for the environment variable {@code variable}. */
+  public static SkyKey key(String variable) {
+    return SkyKey.create(SkyFunctions.ACTION_ENVIRONMENT_VARIABLE, variable);
+  }
+
+  /**
+   * Returns a map of environment variable key => values, getting them from Skyframe. Returns null
+   * if and only if some dependencies from Skyframe still need to be resolved.
+   */
+  public static Map<String, String> getEnvironmentView(Environment env, Iterable<String> keys)
+      throws InterruptedException {
+    ImmutableList.Builder<SkyKey> skyframeKeysBuilder = ImmutableList.builder();
+    for (String key : keys) {
+      skyframeKeysBuilder.add(key(key));
+    }
+    ImmutableList<SkyKey> skyframeKeys = skyframeKeysBuilder.build();
+    Map<SkyKey, SkyValue> values = env.getValues(skyframeKeys);
+    if (env.valuesMissing()) {
+      return null;
+    }
+    // To return the initial order and support null values, we use a LinkedHashMap.
+    LinkedHashMap<String, String> result = new LinkedHashMap<>();
+    for (SkyKey key : skyframeKeys) {
+      ClientEnvironmentValue value = (ClientEnvironmentValue) values.get(key);
+      result.put(key.argument().toString(), value.getValue());
+    }
+    return Collections.unmodifiableMap(result);
+  }
+}