Allow Label instances as keys in select

site/docs/skylark/macros.md

@@ -143,6 +143,38 @@ macro), use the function [native.package_name()](lib/native.html#package_name).
 Note that `native` can only be used in `.bzl` files, and not in `WORKSPACE` or
 `BUILD` files.
 
+## Label resolution in macros
+
+Since macros are evaluated in the [loading phase](concepts.md#evaluation-model),
+label strings such as `"//foo:bar"` that occur in a macro are interpreted
+relative to the `BUILD` file in which the macro is used rather than relative to
+the `.bzl` file in which it is defined. This behavior is generally undesirable
+for macros that are meant to be used in other repositories, e.g. because they
+are part of a published Starlark ruleset.
+
+To get the same behavior as for Starlark rules, wrap the label strings with the
+[`Label`](lib/Label.html#Label) constructor:
+
+```python
+# @my_ruleset//rules:defs.bzl
+def my_cc_wrapper(name, deps = [], **kwargs):
+ native.cc_library(
+ name = name,
+ deps = deps + select({
+ # Due to the use of Label, this label is resolved within @my_ruleset,
+ # regardless of its site of use.
+ Label("//config:needs_foo"): [
+ # Due to the use of Label, this label will resolve to the correct target
+ # even if the canonical name of @dep_of_my_ruleset should be different
+ # in the main workspace, e.g. due to repo mappings.
+ Label("@dep_of_my_ruleset//tools:foo"),
+ ],
+ "//conditions:default": [],
+ }),
+ **kwargs,
+ )
+```
+
 ## Debugging
 
 * `bazel query --output=build //my/path:all` will show you how the `BUILD` file

src/main/java/com/google/devtools/build/lib/packages/SelectorList.java

@@ -16,6 +16,7 @@
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.collect.nestedset.Depset;
 import java.util.Arrays;
 import java.util.List;
@@ -84,9 +85,9 @@ public static Object select(Dict<?, ?> dict, String noMatchError) throws EvalExc
  + " to match");
  }
  for (Object key : dict.keySet()) {
- if (!(key instanceof String)) {
+ if (!(key instanceof String || key instanceof Label)) {
  throw Starlark.errorf(
- "select: got %s for dict key, want a label string", Starlark.type(key));
+ "select: got %s for dict key, want a Label or label string", Starlark.type(key));
  }
  }
  return SelectorList.of(new SelectorValue(dict, noMatchError));

src/main/java/com/google/devtools/build/lib/packages/StarlarkLibrary.java

@@ -330,8 +330,10 @@ public Depset depset(
  name = "x",
  positional = true,
  doc =
- "A dict that maps configuration conditions to values. Each key is a label string"
- + " that identifies a config_setting instance."),
+ "A dict that maps configuration conditions to values. Each key is a "
+ + "<a href=\"$BE_ROOT/../skylark/lib/Label.html\">Label</a> or a label string"
+ + " that identifies a config_setting, constraint_setting, or constraint_value"
+ + " instance."),
  @Param(
  name = "no_match_error",
  defaultValue = "''",

src/main/java/com/google/devtools/build/lib/starlarkbuildapi/StarlarkRuleFunctionsApi.java

@@ -579,10 +579,11 @@ StarlarkAspectApi aspect(
  @StarlarkMethod(
  name = "Label",
  doc =
- "Creates a Label referring to a BUILD target. Use this function only when you want to"
- + " give a default value for the label attributes. The argument must refer to an"
- + " absolute label. The repo part of the label (or its absence) is interpreted in the"
- + " context of the repo where this Label() call appears. Example: <br><pre"
+ "Creates a Label referring to a BUILD target. Use this function when you want to give a"
+ + " default value for the label attributes of a rule or when referring to a target"
+ + " via an absolute label from a macro. The argument must refer to an absolute label."
+ + " The repo part of the label (or its absence) is interpreted in the context of"
+ + " the repo where this Label() call appears. Example: <br><pre"
  + " class=language-python>Label(\"//tools:default\")</pre>",
  parameters = {
  @Param(name = "label_string", doc = "the label string."),

src/test/java/com/google/devtools/build/lib/analysis/ConfigurableAttributesTest.java

@@ -427,7 +427,8 @@ public void configKeyTypeChecking_Int() throws Exception {
  " name = 'int_key',",
  " srcs = select({123: ['a.java']})",
  ")");
- assertTargetError("//java/foo:int_key", "select: got int for dict key, want a label string");
+ assertTargetError("//java/foo:int_key",
+ "select: got int for dict key, want a Label or label string");
  }
 
  @Test
@@ -439,7 +440,8 @@ public void configKeyTypeChecking_Bool() throws Exception {
  " name = 'bool_key',",
  " srcs = select({True: ['a.java']})",
  ")");
- assertTargetError("//java/foo:bool_key", "select: got bool for dict key, want a label string");
+ assertTargetError("//java/foo:bool_key",
+ "select: got bool for dict key, want a Label or label string");
  }
 
  @Test
@@ -452,7 +454,7 @@ public void configKeyTypeChecking_None() throws Exception {
  " srcs = select({None: ['a.java']})",
  ")");
  assertTargetError(
- "//java/foo:none_key", "select: got NoneType for dict key, want a label string");
+ "//java/foo:none_key", "select: got NoneType for dict key, want a Label or label string");
  }
 
  @Test
@@ -1569,4 +1571,48 @@ public void publicVisibilityConfigSetting_defaultIsPrivate() throws Exception {
  assertThat(getConfiguredTarget("//a:binary")).isNotNull();
  assertNoEvents();
  }
+
+ @Test
+ public void selectWithLabelKeysInMacro() throws Exception {
+ writeConfigRules();
+ scratch.file("java/BUILD");
+ scratch.file("java/macros.bzl",
+ "def my_java_binary(name, deps = [], **kwargs):",
+ " native.java_binary(",
+ " name = name,",
+ " deps = select({",
+ " Label('//conditions:a'): [Label('//java/foo:a')],",
+ " '//conditions:b': [Label('//java/foo:b')],",
+ " }) + select({",
+ " '//conditions:a': [Label('//java/foo:a2')],",
+ " Label('//conditions:b'): [Label('//java/foo:b2')],",
+ " }),",
+ " **kwargs,",
+ " )"
+ );
+ scratch.file("java/foo/BUILD",
+ "load('//java:macros.bzl', 'my_java_binary')",
+ "my_java_binary(",
+ " name = 'binary',",
+ " srcs = ['binary.java'],",
+ ")",
+ "java_library(",
+ " name = 'a',",
+ " srcs = ['a.java'])",
+ "java_library(",
+ " name = 'b',",
+ " srcs = ['b.java'])",
+ "java_library(",
+ " name = 'a2',",
+ " srcs = ['a2.java'])",
+ "java_library(",
+ " name = 'b2',",
+ " srcs = ['b2.java'])");
+
+ checkRule(
+ "//java/foo:binary",
+ "--foo=b",
+ /*expected:*/ ImmutableList.of("bin java/foo/libb.jar", "bin java/foo/libb2.jar"),
+ /*not expected:*/ ImmutableList.of("bin java/foo/liba.jar", "bin java/foo/liba2.jar"));
+ }
 }