1 files changed, 253 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/SkylarkEnvironment.java b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkEnvironment.java
new file mode 100644
index 0000000000..7e6f4140a4
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+++ b/src/main/java/com/google/devtools/build/lib/syntax/SkylarkEnvironment.java
@@ -0,0 +1,253 @@
+// Copyright 2014 Google Inc. 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.syntax;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.events.Event;
+import com.google.devtools.build.lib.events.EventHandler;
+import com.google.devtools.build.lib.util.Fingerprint;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+
+import javax.annotation.Nullable;
+
+/**
+ * The environment for Skylark.
+ */
+public class SkylarkEnvironment extends Environment {
+
+  /**
+   * This set contains the variable names of all the successful lookups from the global
+   * environment. This is necessary because if in a function definition something
+   * reads a global variable after which a local variable with the same name is assigned an
+   * Exception needs to be thrown.
+   */
+  private final Set<String> readGlobalVariables = new HashSet<>();
+
+  private ImmutableList<String> stackTrace;
+
+  @Nullable private String fileContentHashCode;
+
+  /**
+   * Creates a Skylark Environment for function calling, from the global Environment of the
+   * caller Environment (which must be a Skylark Environment).
+   */
+  public static SkylarkEnvironment createEnvironmentForFunctionCalling(
+      Environment callerEnv, SkylarkEnvironment definitionEnv,
+      UserDefinedFunction function) throws EvalException {
+    if (callerEnv.getStackTrace().contains(function.getName())) {
+      throw new EvalException(function.getLocation(), "Recursion was detected when calling '"
+          + function.getName() + "' from '" + Iterables.getLast(callerEnv.getStackTrace()) + "'");
+    }
+    ImmutableList<String> stackTrace = new ImmutableList.Builder<String>()
+        .addAll(callerEnv.getStackTrace())
+        .add(function.getName())
+        .build();
+    SkylarkEnvironment childEnv =
+        // Always use the caller Environment's EventHandler. We cannot assume that the
+        // definition Environment's EventHandler is still working properly.
+        new SkylarkEnvironment(definitionEnv, stackTrace, callerEnv.eventHandler);
+    try {
+      for (String varname : callerEnv.propagatingVariables) {
+        childEnv.updateAndPropagate(varname, callerEnv.lookup(varname));
+      }
+    } catch (NoSuchVariableException e) {
+      // This should never happen.
+      throw new IllegalStateException(e);
+    }
+    childEnv.disabledVariables = callerEnv.disabledVariables;
+    childEnv.disabledNameSpaces = callerEnv.disabledNameSpaces;
+    return childEnv;
+  }
+
+  private SkylarkEnvironment(SkylarkEnvironment definitionEnv, ImmutableList<String> stackTrace,
+      EventHandler eventHandler) {
+    super(definitionEnv.getGlobalEnvironment());
+    this.stackTrace = stackTrace;
+    this.eventHandler = Preconditions.checkNotNull(eventHandler,
+        "EventHandler cannot be null in an Environment which calls into Skylark");
+  }
+
+  /**
+   * Creates a global SkylarkEnvironment.
+   */
+  public SkylarkEnvironment(EventHandler eventHandler, String astFileContentHashCode) {
+    super();
+    stackTrace = ImmutableList.of();
+    this.eventHandler = eventHandler;
+    this.fileContentHashCode = astFileContentHashCode;
+  }
+
+  @VisibleForTesting
+  public SkylarkEnvironment(EventHandler eventHandler) {
+    this(eventHandler, null);
+  }
+
+  public SkylarkEnvironment(SkylarkEnvironment globalEnv) {
+    super(globalEnv);
+    stackTrace = ImmutableList.of();
+    this.eventHandler = globalEnv.eventHandler;
+  }
+
+  @Override
+  public ImmutableList<String> getStackTrace() {
+    return stackTrace;
+  }
+
+  /**
+   * Clones this Skylark global environment.
+   */
+  public SkylarkEnvironment cloneEnv(EventHandler eventHandler) {
+    Preconditions.checkArgument(isGlobalEnvironment());
+    SkylarkEnvironment newEnv = new SkylarkEnvironment(eventHandler, this.fileContentHashCode);
+    for (Entry<String, Object> entry : env.entrySet()) {
+      newEnv.env.put(entry.getKey(), entry.getValue());
+    }
+    for (Map.Entry<Class<?>, Map<String, Function>> functionMap : functions.entrySet()) {
+      newEnv.functions.put(functionMap.getKey(), functionMap.getValue());
+    }
+    return newEnv;
+  }
+
+  /**
+   * Returns the global environment. Only works for Skylark environments. For the global Skylark
+   * environment this method returns this Environment.
+   */
+  public SkylarkEnvironment getGlobalEnvironment() {
+    // If there's a parent that's the global environment, otherwise this is.
+    return parent != null ? (SkylarkEnvironment) parent : this;
+  }
+
+  /**
+   * Returns true if this is a Skylark global environment.
+   */
+  public boolean isGlobalEnvironment() {
+    return parent == null;
+  }
+
+  /**
+   * Returns true if varname has been read as a global variable.
+   */
+  public boolean hasBeenReadGlobalVariable(String varname) {
+    return readGlobalVariables.contains(varname);
+  }
+
+  @Override
+  public boolean isSkylarkEnabled() {
+    return true;
+  }
+
+  /**
+   * @return the value from the environment whose name is "varname".
+   * @throws NoSuchVariableException if the variable is not defined in the environment.
+   */
+  @Override
+  public Object lookup(String varname) throws NoSuchVariableException {
+    if (disabledVariables.contains(varname)) {
+      throw new NoSuchVariableException(varname);
+    }
+    Object value = env.get(varname);
+    if (value == null) {
+      if (parent != null && parent.hasVariable(varname)) {
+        readGlobalVariables.add(varname);
+        return parent.lookup(varname);
+      }
+      throw new NoSuchVariableException(varname);
+    }
+    return value;
+  }
+
+  /**
+   * Like <code>lookup(String)</code>, but instead of throwing an exception in
+   * the case where "varname" is not defined, "defaultValue" is returned instead.
+   */
+  @Override
+  public Object lookup(String varname, Object defaultValue) {
+    throw new UnsupportedOperationException();
+  }
+
+  /**
+   * Updates the value of variable "varname" in the environment, corresponding
+   * to an AssignmentStatement.
+   */
+  @Override
+  public void update(String varname, Object value) {
+    Preconditions.checkNotNull(value, "update(value == null)");
+    env.put(varname, value);
+  }
+
+  /**
+   * Returns the class of the variable or null if the variable does not exist. This function
+   * works only in the local Environment, it doesn't check the global Environment.
+   */
+  public Class<?> getVariableType(String varname) {
+    Object variable = env.get(varname);
+    return variable != null ? EvalUtils.getSkylarkType(variable.getClass()) : null;
+  }
+
+  /**
+   * Removes the functions and the modules (i.e. the symbol of the module from the top level
+   * Environment and the functions attached to it) from the Environment which should be present
+   * only during the loading phase.
+   */
+  public void disableOnlyLoadingPhaseObjects() {
+    List<String> objectsToRemove = new ArrayList<>();
+    List<Class<?>> modulesToRemove = new ArrayList<>();
+    for (Map.Entry<String, Object> entry : env.entrySet()) {
+      Object object = entry.getValue();
+      if (object instanceof SkylarkFunction) {
+        if (((SkylarkFunction) object).isOnlyLoadingPhase()) {
+          objectsToRemove.add(entry.getKey());
+        }
+      } else if (object.getClass().isAnnotationPresent(SkylarkModule.class)) {
+        if (object.getClass().getAnnotation(SkylarkModule.class).onlyLoadingPhase()) {
+          objectsToRemove.add(entry.getKey());
+          modulesToRemove.add(entry.getValue().getClass());
+        }
+      }
+    }
+    for (String symbol : objectsToRemove) {
+      disabledVariables.add(symbol);
+    }
+    for (Class<?> moduleClass : modulesToRemove) {
+      disabledNameSpaces.add(moduleClass);
+    }
+  }
+
+  public void handleEvent(Event event) {
+    eventHandler.handle(event);
+  }
+
+  /**
+   * Returns a hash code calculated from the hash code of this Environment and the
+   * transitive closure of other Environments it loads.
+   */
+  public String getTransitiveFileContentHashCode() {
+    Fingerprint fingerprint = new Fingerprint();
+    fingerprint.addString(Preconditions.checkNotNull(fileContentHashCode));
+    // Calculate a new hash from the hash of the loaded Environments.
+    for (SkylarkEnvironment env : importedExtensions.values()) {
+      fingerprint.addString(env.getTransitiveFileContentHashCode());
+    }
+    return fingerprint.hexDigestAndReset();
+  }
+}