Add environ attribute to repository_rule

This environ attribute let the repository rule implementor describes
on which environment variable change a repository should be refetched.

RELNOTES[NEW]: environ parameter to the repository_rule function let
defines a list of environment variables for which a change of value
will trigger a repository refetching.

Design doc: https://bazel.build/designs/2016/10/18/repository-invalidation.html [step 3 & 4]

Fixes #1595.

--
Change-Id: Ibc2f93e69cb08baf86107cc9a9428b7a0eba1bac
Reviewed-on: https://cr.bazel.build/8139
PiperOrigin-RevId: 147345203
MOS_MIGRATED_REVID=147345203

1 files changed, 55 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/repository/RepositoryFunction.java b/src/main/java/com/google/devtools/build/lib/rules/repository/RepositoryFunction.java
index 354d30f4c3..f0ad02a67c 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/repository/RepositoryFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/repository/RepositoryFunction.java
@@ -26,6 +26,7 @@ import com.google.devtools.build.lib.packages.BuildFileContainsErrorsException;
 import com.google.devtools.build.lib.packages.NoSuchPackageException;
 import com.google.devtools.build.lib.packages.Package;
 import com.google.devtools.build.lib.packages.Rule;
+import com.google.devtools.build.lib.skyframe.ActionEnvironmentFunction;
 import com.google.devtools.build.lib.skyframe.FileSymlinkException;
 import com.google.devtools.build.lib.skyframe.FileValue;
 import com.google.devtools.build.lib.skyframe.InconsistentFilesystemException;
@@ -47,6 +48,7 @@ import com.google.devtools.build.skyframe.SkyKey;
 import java.io.IOException;
 import java.nio.charset.Charset;
 import java.util.Map;
+import java.util.Objects;
 import javax.annotation.Nullable;
 
 /**
@@ -164,6 +166,59 @@ public abstract class RepositoryFunction {
   }
 
   /**
+   * A method that can be called from a implementation of
+   * {@link #fetch(Rule, Path, BlazeDirectories, Environment, Map)} to declare a list of Skyframe
+   * dependencies on environment variable. It also add the information to the marker file. It
+   * returns the list of environment variable on which the function depends, or null if the skyframe
+   * function needs to be restarted.
+   */
+  protected Map<String, String> declareEnvironmentDependencies(Map<String, String> markerData,
+      Environment env, Iterable<String> keys) throws InterruptedException {
+    Map<String, String> environ = ActionEnvironmentFunction.getEnvironmentView(env, keys);
+
+    // Returns true if there is a null value and we need to wait for some dependencies.
+    if (environ == null) {
+      return null;
+    }
+    // Add the dependencies to the marker file
+    for (Map.Entry<String, String> value : environ.entrySet()) {
+      markerData.put("ENV:" + value.getKey(), value.getValue());
+    }
+    return environ;
+  }
+
+  /**
+   * Verify marker data previously saved by
+   * {@link #declareEnvironmentDependencies(Map, Environment, Iterable)}. This function is to be
+   * called from a {@link #verifyMarkerData(Rule, Map, Environment)} function to verify the values
+   * for environment variables.
+   */
+  protected boolean verifyEnvironMarkerData(Map<String, String> markerData, Environment env,
+      Iterable<String> keys) throws InterruptedException {
+    Map<String, String> environ = ActionEnvironmentFunction.getEnvironmentView(env, keys);
+    if (env.valuesMissing()) {
+      return false; // Returns false so caller knows to return immediately
+    }
+    // Verify that all environment variable in the marker file are also in keys
+    for (String key : markerData.keySet()) {
+      if (key.startsWith("ENV:") && !environ.containsKey(key.substring(4))) {
+        return false;
+      }
+    }
+    // Now verify the values of the marker data
+    for (Map.Entry<String, String> value : environ.entrySet()) {
+      if (!markerData.containsKey("ENV:" + value.getKey())) {
+        return false;
+      }
+      String markerValue = markerData.get("ENV:" + value.getKey());
+      if (!Objects.equals(markerValue, value.getValue())) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  /**
    * Whether fetching is done using local operations only.
    *
    * <p>If this is false, Bazel may decide not to re-fetch the repository, for example when the