src/main/java/com/google/devtools/build/lib/rules/genquery/GenQueryRule.java

// Copyright 2015 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.genquery;

import static com.google.devtools.build.lib.packages.Attribute.attr;
import static com.google.devtools.build.lib.packages.BuildType.LABEL_LIST;
import static com.google.devtools.build.lib.syntax.Type.BOOLEAN;
import static com.google.devtools.build.lib.syntax.Type.STRING;
import static com.google.devtools.build.lib.syntax.Type.STRING_LIST;

import com.google.devtools.build.lib.analysis.BaseRuleClasses;
import com.google.devtools.build.lib.analysis.RuleDefinition;
import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
import com.google.devtools.build.lib.packages.RuleClass;
import com.google.devtools.build.lib.packages.RuleClass.Builder;

/**
 * Rule definition for genquery the rule.
 */
public final class GenQueryRule implements RuleDefinition {
  @Override
  public RuleClass build(Builder builder, RuleDefinitionEnvironment env) {
    return builder
        /* <!-- #BLAZE_RULE(genquery).ATTRIBUTE(scope) -->
        The scope of the query. The query is not allowed to
        touch targets outside the transitive closure of these targets.
        <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
        .add(attr("scope", LABEL_LIST).mandatory().legacyAllowAnyFileType())
        /* <!-- #BLAZE_RULE(genquery).ATTRIBUTE(strict) -->
        If true, targets whose queries escape the transitive closure of their
        scopes will fail to build. If false, Blaze will print a warning and skip
        whatever query path led it outside of the scope, while completing the rest
        of the query.
        <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
        .add(attr("strict", BOOLEAN).value(true))
        /* <!-- #BLAZE_RULE(genquery).ATTRIBUTE(expression) -->
        The query to be executed.
        <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
        .add(attr("expression", STRING).mandatory())
        /* <!-- #BLAZE_RULE(genquery).ATTRIBUTE(opts) -->
        The options that are passed to the query engine.
        These correspond to the command line options that can be passed to
        <code>blaze query</code>. The only query options that are not allowed here
        are <code>--keep_going</code> and <code>--order_output</code>.
        <!-- #END_BLAZE_RULE.ATTRIBUTE --> */
        .add(attr("opts", STRING_LIST))
        .build();
  }

  @Override
  public Metadata getMetadata() {
    return RuleDefinition.Metadata.builder()
        .name("genquery")
        .ancestors(BaseRuleClasses.RuleBase.class)
        .factoryClass(GenQuery.class)
        .build();
  }
}

/*<!-- #BLAZE_RULE (NAME = genquery, TYPE = LIBRARY, FAMILY = General)[GENERIC_RULE] -->

  <p>
  <code>genquery()</code> runs a query specified in the
    <a href="../query.html">Blaze query language</a> and dumps the result
    into a file.
  </p>
  <p>
    In order to keep the build consistent, the query is allowed only to visit
    the transitive closure of the targets specified in the <code>scope</code>
    attribute. Queries violating this rule will fail during execution if
    <code>strict</code> is unspecified or true (if <code>strict</code> is false,
    the out of scope targets will simply be skipped with a warning). The
    easiest way to make sure this does not happen is to mention the same labels
    in the scope as in the query expression.
  </p>
  <p>
    The only difference between the queries allowed here and on the command
    line is that queries containing wildcard target specifications (e.g.
    <code>//pkg:*</code> or <code>//pkg:all</code>) are not allowed here.
    The reasons for this are two-fold: first, because <code>genquery</code> has
    to specify a scope to prevent targets outside the transitive closure of the
    query to influence its output; and, second, because <code>BUILD</code> files
    do not support wildcard dependencies (e.g. <code>deps=["//a/..."]</code>
    is not allowed).
  </p>
  <p>
    The genquery's output is ordered using <code>--order_output=full</code> in
    order to enforce deterministic output.
  <p>
    The name of the output file is the name of the rule.
  </p>

<h4 id="genquery_examples">Examples</h4>
  <p>
    This example writes the list of the labels in the transitive closure of the
    specified target to a file.
  </p>

<pre class="code">
genquery(
    name = "kiwi-deps",
    expression = "deps(//kiwi:kiwi_lib)",
    scope = ["//kiwi:kiwi_lib"],
)
</pre>

<!-- #END_BLAZE_RULE -->*/