src/main/java/com/google/devtools/build/lib/rules/python/PyRuleClasses.java

// Copyright 2014 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.rules.python;

import com.google.devtools.build.lib.analysis.LanguageDependentFragment.LibraryLanguage;
import com.google.devtools.build.lib.packages.RawAttributeMapper;
import com.google.devtools.build.lib.packages.RuleClass;
import com.google.devtools.build.lib.packages.RuleTransitionFactory;
import com.google.devtools.build.lib.syntax.Type;
import com.google.devtools.build.lib.util.FileType;

/**
 * Rule definitions for Python rules.
 */
public class PyRuleClasses {

  public static final FileType PYTHON_SOURCE = FileType.of(".py");
  public static final LibraryLanguage LANGUAGE = new LibraryLanguage("Python");

  /**
   * Input for {@link RuleClass.Builder#cfg(RuleTransitionFactory)}: if
   * {@link PythonOptions#forcePython} is unset, sets the Python version according to the rule's
   * default Python version. Assumes the rule has the expected attribute for this setting.
   *
   * <p>Since this is a configuration transition, this propagates to the rules' transitive deps.
   */
  public static final RuleTransitionFactory DEFAULT_PYTHON_VERSION_TRANSITION =
      (rule) ->
          new PythonVersionTransition(
              PythonVersion.parse(
                  RawAttributeMapper.of(rule).get("default_python_version", Type.STRING),
                  PythonVersion.ALL_VALUES));
}