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// 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.rules.workspace;
import static com.google.devtools.build.lib.packages.Attribute.attr;
import static com.google.devtools.build.lib.packages.Type.LABEL;
import com.google.devtools.build.lib.analysis.BaseRuleClasses.BaseRule;
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.RuleClassType;
/**
* Binds an existing target to a target in the virtual //external package.
*/
public final class BindRule implements RuleDefinition {
@Override
public RuleClass build(RuleClass.Builder builder, RuleDefinitionEnvironment environment) {
return builder
/* <!-- #BLAZE_RULE(bind).ATTRIBUTE(actual) -->
The target to be aliased.
${SYNOPSIS}
<p>This target must exist, but can be any type of rule (including bind).</p>
<!-- #END_BLAZE_RULE.ATTRIBUTE --> */
.add(attr("actual", LABEL).allowedFileTypes())
.setWorkspaceOnly()
.build();
}
@Override
public Metadata getMetadata() {
return RuleDefinition.Metadata.builder()
.name("bind")
.type(RuleClassType.WORKSPACE)
.ancestors(BaseRule.class)
.factoryClass(Bind.class)
.build();
}
}
/*<!-- #BLAZE_RULE (NAME = bind, TYPE = OTHER, FAMILY = General)[GENERIC_RULE] -->
${ATTRIBUTE_SIGNATURE}
<p>Gives a target an alias in the <code>//external</code> package.</p>
${ATTRIBUTE_DEFINITION}
<p>The <code>//external</code> package is not a "normal" package: there is no external/ directory,
so it can be thought of as a "virtual package" that contains all bound targets.</p>
<h4 id="bind_examples">Examples</h4>
<p>To give a target an alias, bind it in the <i>WORKSPACE</i> file. For example, suppose there is
a <code>java_library</code> target called <code>//third_party/javacc-v2</code>. This could be
aliased by adding the following to the <i>WORKSPACE</i> file:</p>
<pre class="code">
bind(
name = "javacc-latest",
actual = "//third_party/javacc-v2",
)
</pre>
<p>Now targets can depend on <code>//external:javacc-latest</code> instead of
<code>//third_party/javacc-v2</code>. If javacc-v3 is released, the binding can be updated and
all of the BUILD files depending on <code>//external:javacc-latest</code> will now depend on
javacc-v3 without needing to be edited.</p>
<p>Bind can also be used to refer to external repositories' targets. For example, if there is a
remote repository named <code>@my-ssl</code> imported in the WORKSPACE file. If the
<code>@my-ssl</code> repository has a cc_library target <code>//src:openssl-lib</code>, you
could make this target accessible for your program to depend on by using <code>bind</code>:</p>
<pre class="code">
bind(
name = "openssl",
actual = "@my-ssl//src:openssl-lib",
)
</pre>
<p>BUILD files cannot use labels that include a repository name
("@repository-name//package-name:target-name"), so the only way to depend on a target from
another repository is to <code>bind</code> it in the WORKSPACE file and then refer to it by its
aliased name in <code>//external</code> from a BUILD file.</p>
<p>For example, in a BUILD file, the bound target could be used as follows:</p>
<pre class="code">
cc_library(
name = "sign-in",
srcs = ["sign_in.cc"],
hdrs = ["sign_in.h"],
deps = ["//external:openssl"],
)
</pre>
<p>Within <code>sign_in.cc</code> and <code>sign_in.h</code>, the header files exposed by
<code>//external:openssl</code> can be referred to by their path relative to their repository
root. For example, if the rule definition for <code>@my-ssl//src:openssl-lib</code> looks like
this:</p>
<pre class="code">
cc_library(
name = "openssl-lib",
srcs = ["openssl.cc"],
hdrs = ["openssl.h"],
)
</pre>
<p>Then <code>sign_in.cc</code>'s first lines might look like this:</p>
<pre class="code">
#include "sign_in.h"
#include "src/openssl.h"
</pre>
<!-- #END_BLAZE_RULE -->*/
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