巴泽尔的$地点扩张

我想添加$(location)扩展到rules_scala for jvm_flags我在其中设置依赖项的属性data属性，但失败了：
label '//src/java/com/google/devtools/build/lib:worker' in $(location) expression is not a declared prerequisite of this rule.
我在目标中定义了对该标签的依赖关系data像这样的属性：

scala_specs2_junit_test(
    ...
    data = ["//src/java/com/google/devtools/build/lib:worker"],
    jvm_flags = ["-XX:HeapDumpPath=/some/custom/path", "-Dlocation.expanded=$(location //src/java/com/google/devtools/build/lib:worker)"],
)

当我添加时我看到了ctx.attr.data to the expand_location呼叫扩展有效，但我不太确定为什么这不是黑客。是data确实是特殊情况？

    location_expanded_jvm_flags = []
    for jvm_flag in jvm_flags:
        location_expanded_jvm_flags.append(ctx.expand_location(jvm_flag, ctx.attr.data))

还尝试在java_*规则来源来看看它是如何工作的（因为$(location)那里的扩展支持data属性）但找不到相关的地方。

完整目标：

scala_specs2_junit_test(
    name = "Specs2Tests",
    srcs = ["src/main/scala/scala/test/junit/specs2/Specs2Tests.scala"],
    deps = [":JUnitCompileTimeDep"],
    size = "small",
    suffixes = ["Test"],
    data = ["//src/java/com/google/devtools/build/lib:worker"],
    jvm_flags = ["-XX:HeapDumpPath=/some/custom/path", "-Dlocation.expanded=$(location //src/java/com/google/devtools/build/lib:worker)"],
)

你做对了。

我看了源码，你是对的：srcs, deps, and tools（如果在规则中定义）被添加到标签集中expand_locations明白了。data仅当添加LocationExpander https://github.com/bazelbuild/bazel/blob/7184b6f55a8cb72094a481d056fe89bc7be80c76/src/main/java/com/google/devtools/build/lib/rules/SkylarkRuleImplementationFunctions.java#L375-L378是用创建的allowDataAttributeEntriesInLabel=true，但事实并非如此。这就是为什么你必须将其添加到expand_locations(targets).