src/main/java/com/google/devtools/build/lib/analysis/ShToolchain.java

// 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 static com.google.devtools.build.lib.packages.Attribute.attr;
import static com.google.devtools.build.lib.packages.BuildType.LABEL;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.devtools.build.lib.analysis.ToolchainContext.ResolvedToolchainProviders;
import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
import com.google.devtools.build.lib.analysis.platform.ToolchainInfo;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.packages.Attribute;
import com.google.devtools.build.lib.packages.RuleClass;
import com.google.devtools.build.lib.syntax.EvalException;
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 {

  private static final String TOOLCHAIN_TYPE_ATTR = "$sh_toolchain_type";
  private static final String TOOLCHAIN_TYPE_LABEL = "//tools/sh:toolchain_type";
  private static final String TOOLCHAIN_TYPE_PACKAGE = "tools/sh";

  public static RuleClass.Builder addDependency(
      RuleClass.Builder builder, RuleDefinitionEnvironment env) {
    return addDependency(builder, env.getToolsLabel(TOOLCHAIN_TYPE_LABEL));
  }

  private static RuleClass.Builder addDependency(RuleClass.Builder builder, Label toolchainType) {
    return builder.addRequiredToolchains(toolchainType).add(createAttribute(toolchainType));
  }

  private static Attribute.Builder createAttribute(Label toolchainType) {
    return attr(TOOLCHAIN_TYPE_ATTR, LABEL).value(toolchainType);
  }

  /**
   * 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>DO NOT USE THIS METHOD, use {@link #getToolchainPathOrError} instead. This method exists to
   * allow incremental migration to {@link #getToolchainPathOrError}.
   */
  // TODO(laszlocsomor): update every rule that calls getPathOrError to depend on the shell
  // toolchain, and change their use of getPathOrError to getToolchainPathOrError.
  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;
  }

  /**
   * 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, this method gets the path from the selected shell
   * toolchain. If the path is still null or empty, the method reports an error against the rule.
   *
   * @throws IllegalArgumentException if the rule does not depend on the shell toolchain
   */
  public static PathFragment getToolchainPathOrError(RuleContext ctx) {
    // TODO(laszlocsomor): update every rule that calls getPathOrError to depend on the shell
    // toolchain, and change their use of getPathOrError to getToolchainPathOrError.
    Preconditions.checkState(ctx.attributes().has(TOOLCHAIN_TYPE_ATTR, LABEL));

    PathFragment result = getPath(ctx.getConfiguration());

    if (result.isEmpty()) {
      ResolvedToolchainProviders toolchains =
          (ResolvedToolchainProviders) ctx.getToolchainContext().getResolvedToolchainProviders();

      ToolchainInfo activeToolchain =
          toolchains.getForToolchainType(ctx.attributes().get(TOOLCHAIN_TYPE_ATTR, LABEL));

      if (activeToolchain != null) {
        String path = null;
        try {
          path = (String) activeToolchain.getValue("path");
        } catch (EvalException e) {
          throw new IllegalStateException(e);
        }

        if (path != null && !path.isEmpty()) {
          result = PathFragment.create(path);
        }
      }
    }

    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() {}

  @VisibleForTesting
  public static String getToolchainTypeLabelForTesting() {
    return TOOLCHAIN_TYPE_LABEL;
  }

  @VisibleForTesting
  public static String getToolchainTypePackageForTesting() {
    return TOOLCHAIN_TYPE_PACKAGE;
  }
}