query: expose is_executable

It can be useful to know this, and currently the best proxy appears to
be to look for `attributes.$is_executable` (which isn't documented), and
or-ing that with a match on `rule_class.ends_with("_test")`.

Instead, let's have a clearly documented API here.

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

@@ -45,6 +45,7 @@
 import com.google.devtools.build.lib.packages.AttributeMap;
 import com.google.devtools.build.lib.packages.BuildType;
 import com.google.devtools.build.lib.packages.ConfigurationFragmentPolicy.MissingFragmentPolicy;
+import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.packages.RuleClass.Builder.RuleClassType;
 import com.google.devtools.build.lib.packages.TargetUtils;
@@ -500,7 +501,7 @@ public RuleClass build(RuleClass.Builder builder, RuleDefinitionEnvironment env)
           .add(attr("env", STRING_DICT))
           .add(attr("output_licenses", LICENSE))
           .add(
-              attr("$is_executable", BOOLEAN)
+              attr(Rule.IS_EXECUTABLE_ATTRIBUTE_NAME, BOOLEAN)
                   .value(true)
                   .nonconfigurable("Called from RunCommand.isExecutable, which takes a Target"))
           .build();

src/main/java/com/google/devtools/build/lib/analysis/starlark/StarlarkRuleClassFunctions.java

@@ -82,6 +82,7 @@
 import com.google.devtools.build.lib.packages.MacroInstance;
 import com.google.devtools.build.lib.packages.Package;
 import com.google.devtools.build.lib.packages.PredicateWithMessage;
+import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.packages.RuleClass.Builder.RuleClassType;
 import com.google.devtools.build.lib.packages.RuleFactory;
@@ -170,7 +171,7 @@ public class StarlarkRuleClassFunctions implements StarlarkRuleFunctionsApi {
           .add(attr("args", STRING_LIST))
           .add(attr("output_licenses", LICENSE))
           .addAttribute(
-              attr("$is_executable", BOOLEAN)
+              attr(Rule.IS_EXECUTABLE_ATTRIBUTE_NAME, BOOLEAN)
                   .value(true)
                   .nonconfigurable("Called from RunCommand.isExecutable, which takes a Target")
                   .build())
@@ -268,7 +269,7 @@ public static RuleClass getTestBaseRule(RuleDefinitionEnvironment env) {
                                     + BaseRuleClasses.DEFAULT_COVERAGE_REPORT_GENERATOR_VALUE))))
             .add(attr(":run_under", LABEL).value(RUN_UNDER))
             .addAttribute(
-                attr("$is_executable", BOOLEAN)
+                attr(Rule.IS_EXECUTABLE_ATTRIBUTE_NAME, BOOLEAN)
                     .value(true)
                     .nonconfigurable("Called from RunCommand.isExecutable, which takes a Target")
                     .build());

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

@@ -94,6 +94,8 @@ public class Rule implements Target, DependencyFilter.AttributeInfoProvider {
 
   private static final OutputFile[] NO_OUTPUTS = new OutputFile[0];
 
+  public static final String IS_EXECUTABLE_ATTRIBUTE_NAME = "$is_executable";
+
   private final Package pkg;
   private final Label label;
   private final RuleClass ruleClass;
@@ -1281,6 +1283,13 @@ public boolean useToolchainResolution() {
     }
   }
 
+  public boolean isExecutable() {
+    if (getRuleClassObject().hasAttr(IS_EXECUTABLE_ATTRIBUTE_NAME, Type.BOOLEAN)) {
+      return NonconfigurableAttributeMapper.of(this).get(IS_EXECUTABLE_ATTRIBUTE_NAME, Type.BOOLEAN);
+    }
+    return false;
+  }
+
   public RepositoryName getRepository() {
     return label.getPackageIdentifier().getRepository();
   }

src/main/java/com/google/devtools/build/lib/query2/query/output/ProtoOutputFormatter.java

@@ -47,6 +47,7 @@
 import com.google.devtools.build.lib.packages.ProtoUtils;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.Target;
+import com.google.devtools.build.lib.packages.TargetUtils;
 import com.google.devtools.build.lib.packages.Type;
 import com.google.devtools.build.lib.packages.Types;
 import com.google.devtools.build.lib.query2.common.CommonQueryOptions;
@@ -201,6 +202,8 @@ public Build.Target toTargetProtoBuffer(
                     BaseEncoding.base16().lowerCase().encode(transitiveDigest))); // hexify
       }
 
+      rulePb.setIsExecutable(rule.isExecutable() || TargetUtils.isTestRule(target));
+
       ImmutableMap<Aspect, ImmutableMultimap<Attribute, Label>> aspectsDependencies =
           aspectResolver.computeAspectDependencies(target, dependencyFilter);
       if (!aspectsDependencies.isEmpty()) {

src/main/java/com/google/devtools/build/lib/rules/genrule/GenRuleBaseRule.java

@@ -27,6 +27,7 @@
 import com.google.devtools.build.lib.packages.Attribute;
 import com.google.devtools.build.lib.packages.AttributeMap;
 import com.google.devtools.build.lib.packages.BuildType;
+import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.packages.RuleClass.Builder.RuleClassType;
 import com.google.devtools.build.lib.util.FileTypeSet;
@@ -276,12 +277,13 @@ expanded to Windows style paths (with backslash).
             attr("executable", BOOLEAN)
                 .value(false)
                 .nonconfigurable(
-                    "Used in computed default for $is_executable, which is itself non-configurable"
+                    "Used in computed default for " + Rule.IS_EXECUTABLE_ATTRIBUTE_NAME
+                        + " which is itself non-configurable"
                         + " (and thus expects its dependencies to be non-configurable), because"
-                        + " $is_executable  is called from RunCommand.isExecutable, which has no"
-                        + " configuration context"))
+                        + " " + Rule.IS_EXECUTABLE_ATTRIBUTE_NAME + " is called from "
+                        + " RunCommand.isExecutable, which has no configuration context"))
         .add(
-            attr("$is_executable", BOOLEAN)
+            attr(Rule.IS_EXECUTABLE_ATTRIBUTE_NAME, BOOLEAN)
                 .nonconfigurable("Called from RunCommand.isExecutable, which takes a Target")
                 .value(
                     new Attribute.ComputedDefault() {

src/main/java/com/google/devtools/build/lib/rules/starlarkdocextract/ModuleInfoExtractor.java

@@ -29,6 +29,7 @@
 import com.google.devtools.build.lib.packages.BuildType;
 import com.google.devtools.build.lib.packages.BuiltinProvider;
 import com.google.devtools.build.lib.packages.MacroClass;
+import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.RuleClass;
 import com.google.devtools.build.lib.packages.RuleClass.Builder.RuleClassType;
 import com.google.devtools.build.lib.packages.StarlarkDefinedAspect;
@@ -401,7 +402,7 @@ protected void visitRule(String qualifiedName, StarlarkRuleFunction ruleFunction
       if (ruleClass.getRuleClassType() == RuleClassType.TEST) {
         ruleInfoBuilder.setTest(true);
       }
-      if (ruleClass.hasAttr("$is_executable", Type.BOOLEAN)) {
+      if (ruleClass.hasAttr(Rule.IS_EXECUTABLE_ATTRIBUTE_NAME, Type.BOOLEAN)) {
         ruleInfoBuilder.setExecutable(true);
       }
 

src/main/java/com/google/devtools/build/lib/runtime/commands/RunCommand.java

@@ -1123,10 +1123,7 @@ private static boolean isExecutableNonTestRule(Target target) {
     if (!(target instanceof Rule rule)) {
       return false;
     }
-    if (rule.getRuleClassObject().hasAttr("$is_executable", Type.BOOLEAN)) {
-      return NonconfigurableAttributeMapper.of(rule).get("$is_executable", Type.BOOLEAN);
-    }
-    return false;
+    return rule.isExecutable();
   }
 
   private static boolean isPlainFile(Target target) {

src/main/protobuf/build.proto

@@ -289,6 +289,9 @@ message Rule {
   // The rule class (e.g., java_library)
   required string rule_class = 2;
 
+  // Whether the rule can be `bazel run` (i.e. is a binary or test rule).
+  optional bool is_executable = 16;
+
   // The BUILD file and line number of the location (formatted as
   // <absolute_path>:<line_number>:<column_number>) in the rule's package's
   // BUILD file where the rule instance was instantiated. The line number will

src/test/java/com/google/devtools/build/lib/packages/RuleTest.java

@@ -279,4 +279,20 @@ private TargetData roundTrip(Target target) throws SerializationException, IOExc
         ImmutableClassToInstanceMap.of(
             RuleClassProvider.class, skyframeExecutor.getRuleClassProviderForTesting()));
   }
+
+  @Test
+  public void testIsExecutable() throws Exception {
+    scratch.file(
+        "x/BUILD",
+        "cc_binary(name = 'cb')",
+        "cc_library(name = 'cl')",
+        "java_binary(name = 'jb')",
+        "java_library(name = 'jl')");
+    Package pkg = getTarget("//x:BUILD").getPackage();
+    assertThat(pkg.getRule("cb").isExecutable()).isTrue();
+    assertThat(pkg.getRule("jb").isExecutable()).isTrue();
+
+    assertThat(pkg.getRule("cl").isExecutable()).isFalse();
+    assertThat(pkg.getRule("jl").isExecutable()).isFalse();
+  }
 }